
A sample post with markdown.

## Inline Highlighting

Sample of inline highlighting `sum = parseInt(num1) + parseInt(num2)`

## Code Blocks

Some Javascript code

```javascript
var num1, num2, sum;
num1 = prompt("Enter first number");
num2 = prompt("Enter second number");
sum = parseInt(num1) + parseInt(num2); // "+" means "add"
alert("Sum = " + sum); // "+" means combine into a string
```

Some Python code 🐍

```python
def fib():
    a, b = 0, 1
    while True:            # First iteration:
        yield a            # yield 0 to start with and then
        a, b = b, a + b    # a will now be 1, and b will also be 1, (0 + 1)

for index, fibonacci_number in zip(range(10), fib()):
     print('{i:3}: {f:3}'.format(i=index, f=fibonacci_number))
```



## Overview

A post on the new features introduced in v1.0. New features:

<TOCInline toc={props.toc} exclude="Overview" toHeading={2} />

First load JS decreased from 43kB to 39kB despite all the new features added! [^1]

[^1]: With the new changes in Nextjs 12, first load JS increase to 45kB.

See [upgrade guide](#upgrade-guide) below if you are migrating from v0 version of the template.

## Theme colors

You can easily modify the theme color by changing the primary attribute in the tailwind config file:

```js:tailwind.config.js
theme: {
    colors: {
      primary: colors.teal,
      gray: colors.neutral,
      ...
    }
  ...
}
```

The primary color attribute should be assigned an object with keys from 50, 100, 200 ... 900 and the corresponding color code values.

Tailwind includes great default color palettes that can be used for theming your own website. Check out [customizing colors documentation page](https://tailwindcss.com/docs/customizing-colors) for the full range of options.

Migrating from v1? You can revert to the previous theme by setting `primary` to `colors.sky` (Tailwind 2.2.2 and above, otherwise `colors.lightBlue`) and changing gray to `colors.gray`.

From v1.1.2+, you can also customize the style of your code blocks easily by modifying the `css/prism.css` stylesheet. Token classnames are compatible with prismjs
so you can copy and adapt token styles from a prismjs stylesheet e.g. [prism themes](https://github.com/PrismJS/prism-themes).

## Xdm MDX compiler

We switched the MDX bundler from [next-mdx-remote](https://github.com/hashicorp/next-mdx-remote) to [mdx-bundler](https://github.com/kentcdodds/mdx-bundler).
This uses [xdm](https://github.com/wooorm/xdm) under the hood, the latest micromark 3 and remark, rehype libraries.

**Warning:** If you were using custom remark or rehype libraries, please upgrade to micromark 3 compatible ones. If you are upgrading, please delete `node_modules` and `package-lock.json` to avoid having past dependencies related issues.

[xdm](https://github.com/wooorm/xdm) contains multiple improvements over [@mdx-js/mdx](https://github.com/mdx-js/mdx), the compiler used internally by next-mdx-remote, but there might be some breaking behaviour changes.
Please check your markdown output to verify.

Some new possibilities include loading components directly in the mdx file using the import syntax and including js code which could be compiled and bundled at the build step.

For example, the following jsx snippet can be used directly in an MDX file to render the page title component:

```jsx
// Or import PageTitle from './components/PageTitle.js' if you are using js
import PageTitle from "./components/PageTitle.tsx";
<PageTitle> Using JSX components in MDX </PageTitle>;
```

The default configuration resolves all components relative to the `components` directory.

**Note**:
Components which require external image loaders also require additional esbuild configuration.
Components which are dependent on global application state on lifecycle like the Nextjs `Link` component would also not work with this setup as each mdx file is built independently.
For such cases, it is better to use component substitution.

## Table of contents component

Inspired by [Docusaurus](https://docusaurus.io/docs/next/markdown-features/inline-toc) and Gatsby's [gatsby-remark-table-of-contents](https://www.gatsbyjs.com/plugins/gatsby-remark-table-of-contents/),
the `toc` variable containing all the top level headings of the document is passed to the MDX file and can be styled accordingly.
To make generating a table of contents (TOC) simple, you can use the existing `TOCInline` component.

For example, the TOC in this post was generated with the following code:

```jsx
<TOCInline toc={props.toc} exclude="Overview" toHeading={2} />
```

You can customise the headings that are displayed by configuring the `fromHeading` and `toHeading` props, or exclude particular headings
by passing a string or a string array to the `exclude` prop. By default, all headings that are of depth 3 or smaller are indented. This can be configured by changing the `indentDepth` property.
A `asDisclosure` prop can be used to render the TOC within an expandable disclosure element.

Here's the full TOC rendered in a disclosure element.

```jsx
<TOCInline toc={props.toc} asDisclosure />
```

<TOCInline toc={props.toc} asDisclosure />

## Layouts

You can map mdx blog content to layout components by configuring the frontmatter field. For example, this post is written with the new `PostSimple` layout!

### Adding new templates

layout templates are stored in the `./layouts` folder. You can add your React components that you want to map to markdown content in this folder.
The component file name must match that specified in the markdown frontmatter `layout` field.

The only required field is `children` which contains the rendered MDX content, though you would probably want to pass in the frontMatter contents and render it in the template.

You can configure the template to take in other fields - see `PostLayout` component for an example.

Here's an example layout which you can further customise:

```jsx
export default function ExampleLayout({ frontMatter, children }) {
  const { date, title } = frontMatter;

  return (
    <SectionContainer>
      <div>{date}</div>
      <h1>{title}</h1>
      <div>{children}</div>
    </SectionContainer>
  );
}
```

### Configuring a blog post frontmatter

Use the `layout` frontmatter field to specify the template you want to map the markdown post to. Here's how the frontmatter of this post looks like:

```
---
title: 'New features in v1'
date: '2021-05-26   '
tags: ['next-js', 'tailwind', 'guide']
draft: false
summary: 'Introducing the new layout features - you can map mdx blog content to layout components by configuring the frontmatter field'
layout: PostSimple
---
```

You can configure the default layout in the respective page section by modifying the `DEFAULT_LAYOUT` variable.
The `DEFAULT_LAYOUT` for blog posts page is set to `PostLayout`.

### Extend

`layout` is mapped to wrapper which wraps the entire MDX content.

```jsx
export const MDXComponents = {
  Image,
  a: CustomLink,
  pre: Pre,
  wrapper: ({ components, layout, ...rest }) => {
    const Layout = require(`../layouts/${layout}`).default;
    return <Layout {...rest} />;
  },
};

export const MDXLayoutRenderer = ({ layout, mdxSource, ...rest }) => {
  const MDXLayout = useMemo(() => getMDXComponent(mdxSource), [mdxSource]);

  return <MDXLayout layout={layout} components={MDXComponents} {...rest} />;
};
```

Use the `MDXLayoutRenderer` component on a page where you want to accept a layout name to map to the desired layout.
You need to pass the layout name from the layout folder (it has to be an exact match).

## Analytics

The template now supports [plausible](https://plausible.io/), [simple analytics](https://simpleanalytics.com/) and google analytics.
Configure `siteMetadata.js` with the settings that correspond with the desired analytics provider.

```js
analytics: {
    // supports plausible, simpleAnalytics or googleAnalytics
    plausibleDataDomain: '', // e.g. tailwind-nextjs-starter-blog.vercel.app
    simpleAnalytics: false, // true or false
    googleAnalyticsId: '', // e.g. UA-000000-2 or G-XXXXXXX
  },
```

Custom events are also supported. You can import the `logEvent` function from `@components/analytics/[ANALYTICS-PROVIDER]` file and call it when
triggering certain events of interest. _Note_: Additional configuration might be required depending on the analytics provider, please check their official
documentation for more information.

## Blog comments system

We have also added support for [giscus](https://github.com/laymonage/giscus), [utterances](https://github.com/utterance/utterances) or disqus.
To enable, simply configure `siteMetadata.js` comments property with the desired provider and settings as specified in the config file.

```js
comment: {
    // Select a provider and use the environment variables associated to it
    // https://vercel.com/docs/environment-variables
    provider: 'giscus', // supported providers: giscus, utterances, disqus
    giscusConfig: {
      // Visit the link below, and follow the steps in the 'configuration' section
      // https://giscus.app/
      repo: process.env.NEXT_PUBLIC_GISCUS_REPO,
      repositoryId: process.env.NEXT_PUBLIC_GISCUS_REPOSITORY_ID,
      category: process.env.NEXT_PUBLIC_GISCUS_CATEGORY,
      categoryId: process.env.NEXT_PUBLIC_GISCUS_CATEGORY_ID,
      mapping: 'pathname', // supported options: pathname, url, title
      reactions: '1', // Emoji reactions: 1 = enable / 0 = disable
      // Send discussion metadata periodically to the parent window: 1 = enable / 0 = disable
      metadata: '0',
      // theme example: light, dark, dark_dimmed, dark_high_contrast
      // transparent_dark, preferred_color_scheme, custom
      theme: 'light',
      // theme when dark mode
      darkTheme: 'transparent_dark',
      // If the theme option above is set to 'custom`
      // please provide a link below to your custom theme css file.
      // example: https://giscus.app/themes/custom_example.css
      themeURL: '',
    },
    utterancesConfig: {
      // Visit the link below, and follow the steps in the 'configuration' section
      // https://utteranc.es/
      repo: process.env.NEXT_PUBLIC_UTTERANCES_REPO,
      issueTerm: '', // supported options: pathname, url, title
      label: '', // label (optional): Comment 💬
      // theme example: github-light, github-dark, preferred-color-scheme
      // github-dark-orange, icy-dark, dark-blue, photon-dark, boxy-light
      theme: '',
      // theme when dark mode
      darkTheme: '',
    },
    disqus: {
      // https://help.disqus.com/en/articles/1717111-what-s-a-shortname
      shortname: process.env.NEXT_PUBLIC_DISQUS_SHORTNAME,
    },
  },
```

## Multiple authors

Information on authors is now split from `siteMetadata.js` and stored in its own `data/authors` folder as a markdown file. Minimally, you will need to have a `default.md` file with authorship information. You can create additional files as required and the file name will be used as the reference to the author.

Here's how an author markdown file might look like:

```md:default.md
---
name: Tails Azimuth
avatar: /static/images/avatar.png
occupation: Professor of Atmospheric Science
company: Stanford University
email: address@yoursite.com
twitter: https://twitter.com/Twitter
linkedin: https://www.linkedin.com
github: https://github.com
---

A long description of yourself...
```

You can use this information in multiple places across the template. For example in the about section of the page, we grab the default author information with this line of code:

```js
const authorDetails = await getFileBySlug("authors", ["default"]);
```

This is rendered in the `AuthorLayout` template.

### Multiple authors in blog post

The frontmatter of a blog post accepts an optional `authors` array field. If no field is specified, it is assumed that the default author is used. Simply pass in an array of authors to render multiple authors associated with a post.

For example, the following frontmatter will display the authors given by `data/authors/default.md` and `data/authors/sparrowhawk.md`

```yaml
title: "My first post"
date: "2021-01-12"
draft: false
summary: "My first post"
authors: ["default", "sparrowhawk"]
```

A demo of a multiple authors post is shown in [Introducing Tailwind Nextjs Starter Blog post](/blog/introducing-tailwind-nextjs-starter-blog).

## Copy button for code blocks

Hover over a code block and you will notice a GitHub-inspired copy button! You can modify `./components/Pre.js` to further customise it.
The component is passed to `MDXComponents` and modifies all `<pre>` blocks.

## Line highlighting and line numbers

Line highlighting and line numbers are now supported out of the box thanks to the new [rehype-prism-plus plugin](https://github.com/timlrx/rehype-prism-plus)

The following javascript code block:

````
```js {1, 3-4} showLineNumbers
var num1, num2, sum
num1 = prompt('Enter first number')
num2 = prompt('Enter second number')
sum = parseInt(num1) + parseInt(num2) // "+" means "add"
alert('Sum = ' + sum) // "+" means combine into a string
```
````

will appear as:

```js {1,3-4} showLineNumbers
var num1, num2, sum;
num1 = prompt("Enter first number");
num2 = prompt("Enter second number");
sum = parseInt(num1) + parseInt(num2); // "+" means "add"
alert("Sum = " + sum); // "+" means combine into a string
```

To modify the styles, change the following class selectors in the `prism.css` file:

```css
.code-highlight {
  @apply float-left min-w-full;
}

.code-line {
  @apply -mx-4 block border-l-4 border-opacity-0 pl-4 pr-4;
}

.code-line.inserted {
  @apply bg-green-500 bg-opacity-20;
}

.code-line.deleted {
  @apply bg-red-500 bg-opacity-20;
}

.highlight-line {
  @apply -mx-4 border-l-4 border-primary-500 bg-gray-700 bg-opacity-50;
}

.line-number::before {
  @apply -ml-2 mr-4 inline-block w-4 text-right text-gray-400;
  content: attr(line);
}
```

## Newletter component (v1.1.3)

Introduced in v1.1.3, the newsletter component gives you an easy way to build an audience. It integrates with the following providers:

- [Mailchimp](https://mailchimp.com/)
- [Buttondown](https://buttondown.email/)
- [Convertkit](https://convertkit.com/)

To use it, specify the provider which you are using in the config file and add the necessary environment variables to the `.env` file.
For more information on the required variables, check out `.env.sample.`

Two components are exported, a default `NewsletterForm` and a `BlogNewsletterForm` component, which is also passed in as an MDX component
and can be used in a blog post:

```jsx
<BlogNewsletterForm title="Like what you are reading?" />
```

<BlogNewsletterForm title="Like what you are reading?" />

The component relies on nextjs's [API routes](https://nextjs.org/docs/api-routes/introduction) which requires a server-side instance of nextjs to be setup
and is not compatible with a 100% static site export. Users should either self-host or use a compatible platform like Vercel or Netlify which supports this functionality.

A static site compatible alternative is to substitute the route in the newsletter component with a form API endpoint provider.

## Bibliography and Citations (v1.2.1)

`rehype-citation` plugin is added to the xdm processing pipeline in v1.2.1. This allows you to easily format citations and insert bibliography from an existing bibtex or CSL-json file.

For example, the following markdown code sample:

```md
Standard citation [@Nash1950]
In-text citations e.g. @Nash1951
Multiple citations [see @Nash1950; @Nash1951, page 50]

**References:**

[^ref]
```

is rendered to the following:

Standard citation [@Nash1950]  
In-text citations e.g. @Nash1951  
Multiple citations [see @Nash1950; @Nash1951, page 50]

**References:**

[^ref]

A bibliography will be inserted at the end of the document, but this can be overwritten by specifying a `[^Ref]` tag at the intended location.
The plugin uses APA citation formation, but also supports the following CSLs, 'apa', 'vancouver', 'harvard1', 'chicago', 'mla', or a path to a user-specified CSL file.

See [rehype-citation readme](https://github.com/timlrx/rehype-citation) for more information on the configuration options.

## Self-hosted font (v1.5.0)

Google font has been replaced with self-hosted font from [Fontsource](https://fontsource.org/). This gives the following [advantages](https://fontsource.org/docs/introduction):

> Self-hosting brings significant performance gains as loading fonts from hosted services, such as Google Fonts, lead to an extra (render blocking) network request. To provide perspective, for simple websites it has been seen to double visual load times.
>
> Fonts remain version locked. Google often pushes updates to their fonts without notice, which may interfere with your live production projects. Manage your fonts like any other NPM dependency.
>
> Commit to privacy. Google does track the usage of their fonts and for those who are extremely privacy concerned, self-hosting is an alternative.

This leads to a smaller font bundle and a 0.1s faster load time ([webpagetest comparison](https://www.webpagetest.org/video/compare.php?tests=220201_AiDcFH_f68a69b758454dd52d8e67493fdef7da,220201_BiDcMC_bf2d53f14483814ba61e794311dfa771)).

To change the default Inter font:

1. Install the preferred [font](https://fontsource.org/fonts) - `npm install -save @fontsource/<font-name>`
2. Update the import at `pages/_app.js`- `import '@fontsource/<font-name>.css'`
3. Update the `fontfamily` property in the tailwind css config file

## Upgrade guide

There are significant portions of the code that has been changed from v0 to v1 including support for layouts and a new mdx engine.

There's also no real reason to change if the previous one serves your needs and it might be easier to copy
the component changes you are interested in to your existing blog rather than migrating everything over.

Nonetheless, if you want to do so and have not changed much of the template, you could clone the new version and copy over the blog post over to the new template.

Another alternative would be to pull the latest template version with the following code:

```bash
git remote add template git@github.com:timlrx/tailwind-nextjs-starter-blog.git
git pull template v1 --allow-unrelated-histories
rm -rf node_modules
```

You can see an example of such a migration in this [commit](https://github.com/timlrx/timlrx.com/commit/bba1c185384fd6d5cdaac15abf802fdcff027286) for my personal blog.

v1 also uses `feed.xml` rather than `index.xml`, to avoid some build issues with Vercel. If you are migrating you should add a redirect to `next.config.js` like so:

```js
async redirects() {
  return [
    {
      source: '/:path/index.xml',
      destination: '/:path/feed.xml',
      permanent: true,
    }
  ]
}
```



The scenic lands of Canada featuring maple leaves, snow-capped mountains, turquoise lakes and Toronto. Take in the sights in this photo gallery exhibition and see how easy it is to replicate with some MDX magic and tailwind classes.

Features images served using `next/image` component. The locally stored images are located in a folder with the following path: `/static/images/canada/[filename].jpg`

Since we are using mdx, we can create a simple responsive flexbox grid to display our images with a few tailwind css classes.

---

# Gallery

<div className="-mx-2 flex flex-wrap overflow-hidden xl:-mx-2">
  <div className="my-1 w-full overflow-hidden px-2 xl:my-1 xl:w-1/2 xl:px-2">
    ![Maple](/static/images/canada/maple.jpg)
  </div>
  <div className="my-1 w-full overflow-hidden px-2 xl:my-1 xl:w-1/2 xl:px-2">
    ![Lake](/static/images/canada/lake.jpg)
  </div>
  <div className="my-1 w-full overflow-hidden px-2 xl:my-1 xl:w-1/2 xl:px-2">
    ![Mountains](/static/images/canada/mountains.jpg)
  </div>
  <div className="my-1 w-full overflow-hidden px-2 xl:my-1 xl:w-1/2 xl:px-2">
    ![Toronto](/static/images/canada/toronto.jpg)
  </div>
</div>

# Implementation

```js
<div className="-mx-2 flex flex-wrap overflow-hidden xl:-mx-2">
  <div className="my-1 w-full overflow-hidden px-2 xl:my-1 xl:w-1/2 xl:px-2">
    ![Maple](/static/images/canada/maple.jpg)
  </div>
  <div className="my-1 w-full overflow-hidden px-2 xl:my-1 xl:w-1/2 xl:px-2">
    ![Lake](/static/images/canada/lake.jpg)
  </div>
  <div className="my-1 w-full overflow-hidden px-2 xl:my-1 xl:w-1/2 xl:px-2">
    ![Mountains](/static/images/canada/mountains.jpg)
  </div>
  <div className="my-1 w-full overflow-hidden px-2 xl:my-1 xl:w-1/2 xl:px-2">
    ![Toronto](/static/images/canada/toronto.jpg)
  </div>
</div>
```

With MDX v2, one can interleave markdown in jsx as shown in the example code.

### Photo Credits

<div>
  Maple photo by [Guillaume
  Jaillet](https://unsplash.com/@i_am_g?utm_source=unsplash&amp;utm_medium=referral&amp;utm_content=creditCopyText)
  on
  [Unsplash](https://unsplash.com/s/photos/canada?utm_source=unsplash&amp;utm_medium=referral&amp;utm_content=creditCopyText)
</div>
<div>
  Mountains photo by [John
  Lee](https://unsplash.com/@john_artifexfilms?utm_source=unsplash&amp;utm_medium=referral&amp;utm_content=creditCopyText)
  on
  [Unsplash](https://unsplash.com/s/photos/canada?utm_source=unsplash&amp;utm_medium=referral&amp;utm_content=creditCopyText)
</div>
<div>
  Lake photo by [Tj
  Holowaychuk](https://unsplash.com/@tjholowaychuk?utm_source=unsplash&amp;utm_medium=referral&amp;utm_content=creditCopyText)
  on
  [Unsplash](https://unsplash.com/s/photos/canada?utm_source=unsplash&amp;utm_medium=referral&amp;utm_content=creditCopyText)
</div>
<div>
  Toronto photo by [Matthew
  Henry](https://unsplash.com/@matthewhenry?utm_source=unsplash&amp;utm_medium=referral&amp;utm_content=creditCopyText)
  on
  [Unsplash](https://unsplash.com/s/photos/canada?utm_source=unsplash&amp;utm_medium=referral&amp;utm_content=creditCopyText)
</div>



# Nested Routes

The blog template supports posts in nested sub-folders. This helps in organisation and can be used to group posts of similar content e.g. a multi-part series. This post is itself an example of a nested route! It's located in the `/data/blog/nested-route` folder.

## How

Simplify create multiple folders inside the main `/data/blog` folder and add your `.md`/`.mdx` files to them. You can even create something like `/data/blog/nested-route/deeply-nested-route/my-post.md`

We use Next.js catch all routes to handle the routing and path creations.

## Use Cases

Here are some reasons to use nested routes

- More logical content organisation (blogs will still be displayed based on the created date)
- Multi-part posts
- Different sub-routes for each author
- Internationalization (though it would be recommended to use [Next.js built-in i8n routing](https://nextjs.org/docs/advanced-features/i18n-routing))

## Note

- The previous/next post links at bottom of the template are currently sorted by date. One could explore modifying the template to refer the reader to the previous/next post in the series, rather than by date.



# Introduction

The tailwind starter blog has out of the box support for [Next.js's built-in image component](https://nextjs.org/docs/api-reference/next/image) and automatically swaps out default image tags in markdown or mdx documents to use the Image component provided.

# Usage

To use in a new page route / javascript file, simply import the image component and call it e.g.

```js
import Image from "next/image";

function Home() {
  return (
    <>
      <h1>My Homepage</h1>
      <Image
        src="/me.png"
        alt="Picture of the author"
        width={500}
        height={500}
      />
      <p>Welcome to my homepage!</p>
    </>
  );
}

export default Home;
```

For a markdown file, the default image tag can be used and the default `img` tag gets replaced by the `Image` component in the build process.

Assuming we have a file called `ocean.jpg` in `data/img/ocean.jpg`, the following line of code would generate the optimized image.

```
![ocean](/static/images/ocean.jpg)
```

Alternatively, since we are using mdx, we can just use the image component directly! Note, that you would have to provide a fixed width and height. The `img` tag method parses the dimension automatically.

```js
<Image alt="ocean" src="/static/images/ocean.jpg" width={256} height={128} />
```

_Note_: If you try to save the image, it is in webp format, if your browser supports it!

![ocean](/static/images/ocean.jpeg)

Photo by [YUCAR FotoGrafik](https://unsplash.com/@yucar?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText)
on [Unsplash](https://unsplash.com/s/photos/sea?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText)

# Benefits

- Smaller image size with Webp (~30% smaller than jpeg)
- Responsive images - the correct image size is served based on the user's viewport
- Lazy loading - images load as they are scrolled to the viewport
- Avoids [Cumulative Layout Shift](https://web.dev/cls/)
- Optimization on demand instead of build-time - no increase in build time!

# Limitations

- Due to the reliance on `next/image`, unless you are using an external image CDN like Cloudinary or Imgix, it is practically required to use Vercel for hosting. This is because the component acts like a serverless function that calls a highly optimized image CDN.

  If you do not want to be tied to Vercel, you can remove `imgToJsx` in `remarkPlugins` in `lib/mdx.js`. This would avoid substituting the default `img` tag.

  Alternatively, one could wait for image optimization at build time to be supported. A different library, [next-optimized-images](https://github.com/cyrilwanner/next-optimized-images) does that, although it requires transforming the images through webpack which is not done here.

- Images from external links are not passed through `next/image`
- All images have to be stored in the `public` folder e.g `/static/images/ocean.jpeg`



# The Time Machine by H. G. Wells

_Title_: The Time Machine

_Author_: H. G. Wells

_Subject_: Science Fiction

_Language_: English

_Source_: [Project Gutenberg](https://www.gutenberg.org/ebooks/35)

## Introduction

The Time Traveller (for so it will be convenient to speak of him) was
expounding a recondite matter to us. His pale grey eyes shone and
twinkled, and his usually pale face was flushed and animated. The fire
burnt brightly, and the soft radiance of the incandescent lights in the
lilies of silver caught the bubbles that flashed and passed in our
glasses. Our chairs, being his patents, embraced and caressed us rather
than submitted to be sat upon, and there was that luxurious
after-dinner atmosphere, when thought runs gracefully free of the
trammels of precision. And he put it to us in this way—marking the
points with a lean forefinger—as we sat and lazily admired his
earnestness over this new paradox (as we thought it) and his fecundity.

“You must follow me carefully. I shall have to controvert one or two
ideas that are almost universally accepted. The geometry, for instance,
they taught you at school is founded on a misconception.”

“Is not that rather a large thing to expect us to begin upon?” said
Filby, an argumentative person with red hair.

“I do not mean to ask you to accept anything without reasonable ground
for it. You will soon admit as much as I need from you. You know of
course that a mathematical line, a line of thickness _nil_, has no real
existence. They taught you that? Neither has a mathematical plane.
These things are mere abstractions.”

“That is all right,” said the Psychologist.

“Nor, having only length, breadth, and thickness, can a cube have a
real existence.”

“There I object,” said Filby. “Of course a solid body may exist. All
real things—”

“So most people think. But wait a moment. Can an _instantaneous_ cube
exist?”

“Don’t follow you,” said Filby.

“Can a cube that does not last for any time at all, have a real
existence?”

Filby became pensive. “Clearly,” the Time Traveller proceeded, “any
real body must have extension in _four_ directions: it must have
Length, Breadth, Thickness, and—Duration. But through a natural
infirmity of the flesh, which I will explain to you in a moment, we
incline to overlook this fact. There are really four dimensions, three
which we call the three planes of Space, and a fourth, Time. There is,
however, a tendency to draw an unreal distinction between the former
three dimensions and the latter, because it happens that our
consciousness moves intermittently in one direction along the latter
from the beginning to the end of our lives.”

“That,” said a very young man, making spasmodic efforts to relight his
cigar over the lamp; “that . . . very clear indeed.”

“Now, it is very remarkable that this is so extensively overlooked,”
continued the Time Traveller, with a slight accession of cheerfulness.
“Really this is what is meant by the Fourth Dimension, though some
people who talk about the Fourth Dimension do not know they mean it. It
is only another way of looking at Time. _There is no difference between
Time and any of the three dimensions of Space except that our
consciousness moves along it_. But some foolish people have got hold of
the wrong side of that idea. You have all heard what they have to say
about this Fourth Dimension?”

“_I_ have not,” said the Provincial Mayor.

“It is simply this. That Space, as our mathematicians have it, is
spoken of as having three dimensions, which one may call Length,
Breadth, and Thickness, and is always definable by reference to three
planes, each at right angles to the others. But some philosophical
people have been asking why _three_ dimensions particularly—why not
another direction at right angles to the other three?—and have even
tried to construct a Four-Dimensional geometry. Professor Simon Newcomb
was expounding this to the New York Mathematical Society only a month
or so ago. You know how on a flat surface, which has only two
dimensions, we can represent a figure of a three-dimensional solid, and
similarly they think that by models of three dimensions they could
represent one of four—if they could master the perspective of the
thing. See?”

“I think so,” murmured the Provincial Mayor; and, knitting his brows,
he lapsed into an introspective state, his lips moving as one who
repeats mystic words. “Yes, I think I see it now,” he said after some
time, brightening in a quite transitory manner.

“Well, I do not mind telling you I have been at work upon this geometry
of Four Dimensions for some time. Some of my results are curious. For
instance, here is a portrait of a man at eight years old, another at
fifteen, another at seventeen, another at twenty-three, and so on. All
these are evidently sections, as it were, Three-Dimensional
representations of his Four-Dimensioned being, which is a fixed and
unalterable thing.

“Scientific people,” proceeded the Time Traveller, after the pause
required for the proper assimilation of this, “know very well that Time
is only a kind of Space. Here is a popular scientific diagram, a
weather record. This line I trace with my finger shows the movement of
the barometer. Yesterday it was so high, yesterday night it fell, then
this morning it rose again, and so gently upward to here. Surely the
mercury did not trace this line in any of the dimensions of Space
generally recognised? But certainly it traced such a line, and that
line, therefore, we must conclude, was along the Time-Dimension.”

“But,” said the Medical Man, staring hard at a coal in the fire, “if
Time is really only a fourth dimension of Space, why is it, and why has
it always been, regarded as something different? And why cannot we move
in Time as we move about in the other dimensions of Space?”

The Time Traveller smiled. “Are you so sure we can move freely in
Space? Right and left we can go, backward and forward freely enough,
and men always have done so. I admit we move freely in two dimensions.
But how about up and down? Gravitation limits us there.”

“Not exactly,” said the Medical Man. “There are balloons.”

“But before the balloons, save for spasmodic jumping and the
inequalities of the surface, man had no freedom of vertical movement.”

“Still they could move a little up and down,” said the Medical Man.

“Easier, far easier down than up.”

“And you cannot move at all in Time, you cannot get away from the
present moment.”

“My dear sir, that is just where you are wrong. That is just where the
whole world has gone wrong. We are always getting away from the present
moment. Our mental existences, which are immaterial and have no
dimensions, are passing along the Time-Dimension with a uniform
velocity from the cradle to the grave. Just as we should travel _down_
if we began our existence fifty miles above the earth’s surface.”

“But the great difficulty is this,” interrupted the Psychologist. ’You
_can_ move about in all directions of Space, but you cannot move about
in Time.”

“That is the germ of my great discovery. But you are wrong to say that
we cannot move about in Time. For instance, if I am recalling an
incident very vividly I go back to the instant of its occurrence: I
become absent-minded, as you say. I jump back for a moment. Of course
we have no means of staying back for any length of Time, any more than
a savage or an animal has of staying six feet above the ground. But a
civilised man is better off than the savage in this respect. He can go
up against gravitation in a balloon, and why should he not hope that
ultimately he may be able to stop or accelerate his drift along the
Time-Dimension, or even turn about and travel the other way?”

“Oh, _this_,” began Filby, “is all—”

“Why not?” said the Time Traveller.

“It’s against reason,” said Filby.

“What reason?” said the Time Traveller.

“You can show black is white by argument,” said Filby, “but you will
never convince me.”

“Possibly not,” said the Time Traveller. “But now you begin to see the
object of my investigations into the geometry of Four Dimensions. Long
ago I had a vague inkling of a machine—”

“To travel through Time!” exclaimed the Very Young Man.

“That shall travel indifferently in any direction of Space and Time, as
the driver determines.”

Filby contented himself with laughter.

“But I have experimental verification,” said the Time Traveller.

“It would be remarkably convenient for the historian,” the Psychologist
suggested. “One might travel back and verify the accepted account of
the Battle of Hastings, for instance!”

“Don’t you think you would attract attention?” said the Medical Man.
“Our ancestors had no great tolerance for anachronisms.”

“One might get one’s Greek from the very lips of Homer and Plato,” the
Very Young Man thought.

“In which case they would certainly plough you for the Little-go. The
German scholars have improved Greek so much.”

“Then there is the future,” said the Very Young Man. “Just think! One
might invest all one’s money, leave it to accumulate at interest, and
hurry on ahead!”

“To discover a society,” said I, “erected on a strictly communistic
basis.”

“Of all the wild extravagant theories!” began the Psychologist.

“Yes, so it seemed to me, and so I never talked of it until—”

“Experimental verification!” cried I. “You are going to verify _that_?”

“The experiment!” cried Filby, who was getting brain-weary.

“Let’s see your experiment anyhow,” said the Psychologist, “though it’s
all humbug, you know.”

The Time Traveller smiled round at us. Then, still smiling faintly, and
with his hands deep in his trousers pockets, he walked slowly out of
the room, and we heard his slippers shuffling down the long passage to
his laboratory.

The Psychologist looked at us. “I wonder what he’s got?”

“Some sleight-of-hand trick or other,” said the Medical Man, and Filby
tried to tell us about a conjuror he had seen at Burslem, but before he
had finished his preface the Time Traveller came back, and Filby’s
anecdote collapsed.


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