What Faraday Meant by Fifteen Pounds to the Inch
Michael Faraday delivered The Chemical History of a Candle as a course of six lectures for a young audience at the Royal Institution, and the book has been in print since 1861. The passage you can type here is 257 characters from the second lecture, and it is not an explanation so much as an invitation: he is holding two brass hemispheres and telling the room that nobody in it will pull them apart.
Every square inch of surface that is contained in the area of that vessel sustains fifteen pounds by weight, or nearly so, when the air is taken out; and you may try your strength presently in seeing whether you can overcome that pressure of the atmosphere.
Michael Faraday, 1861.
Where did the candle lectures come from?
Faraday started the Christmas Lectures at the Royal Institution in 1825, when organized science teaching for children barely existed, and the series has run ever since. The Royal Institution now calls it the oldest science series on television: it was first broadcast in 1936 and has gone out every year since 1966.
The candle course is the best known of them. Faraday chose the humblest object in the room and worked outwards from it to combustion, air, water and respiration, on the argument that no better door into science exists than a burning candle. The text was edited by William Crookes and published in 1861. The copy on Project Gutenberg is a later impression of that edition, with the Chatto and Windus title page dated 1908.
What is he demonstrating in this passage?
He is holding an apparatus of two hollow brass hemispheres, fitted closely together, with a pipe and a tap through which the air inside can be pumped out. While the air is in, the halves come apart in a second. Once the air is gone, the atmosphere presses on the outside with nothing pushing back, and no two people in the audience can separate them.
The number is the point. Fifteen pounds on every square inch is roughly what the atmosphere weighs on any surface at sea level, so the force holding the hemispheres together grows with the size of the sphere. Faraday does not give the pupils a formula. He hands them the apparatus and lets them fail to open it.
What is easy to miss on the first reading?
Faraday had almost no formal schooling. He was apprenticed to a bookbinder and read the books that passed through his hands, which is where his science began. The plain vocabulary in these lectures is not simplification for children; it is how he thought and wrote.
The sentence also shows his method in one move. He states a quantity, then immediately turns it into something the audience will do with their own arms in a moment. A modern textbook would put the demonstration first and the number afterwards, or drop the demonstration entirely.
There is a smaller detail in the punctuation. The semicolon in the middle of the sentence is doing real work: it joins the measurement to the challenge without letting either become a separate sentence, which is exactly how a lecturer keeps a room from applauding too early.
What do you practice by typing this passage?
This is the easiest of the science passages on the site, and it is a good place to start if long texts put you off. There are no digits at all. Fifteen is spelled out, as numbers usually were in printed lectures, so your hands stay on the letter rows and never reach for the number row.
What it does drill is the comma and the semicolon inside a long spoken sentence, plus a handful of longer words among the short ones: surface, contained, sustains, atmosphere. The rhythm is conversational rather than literary, which makes it a fair test of whether you can keep an even pace through a sentence that does not stop where you expect.
| Fact | Detail |
|---|---|
| Author | Michael Faraday, edited by William Crookes |
| Year | 1861 |
| Form | Course of six lectures for a young audience |
| Source edition | Project Gutenberg text of the Crookes edition |
| Characters | 257 in the practice passage, 46 words |
| Level | Easy |
| Trains | Figures written as words, semicolon, technical nouns |
FAQ
What is The Chemical History of a Candle?
Six lectures Faraday gave to a young audience at the Royal Institution, published in 1861, which use a burning candle as the way into combustion, air, water and breathing.
What does fifteen pounds to the inch mean?
That the atmosphere presses on every square inch of a surface with about fifteen pounds of force. Faraday uses it to explain why two brass hemispheres cannot be pulled apart once the air between them is pumped out.
Did Faraday start the Christmas Lectures?
Yes, in 1825. The Royal Institution has run them every year since, and they were first broadcast on television in 1936.
Is this passage good for a beginner?
It is marked easy and contains no digits, so it suits anyone still learning the letter rows. The only awkward reaches are the semicolon and the commas.
Where can I read the whole book?
The full text of the Crookes edition is free on Project Gutenberg, linked at the end of this page.
Type it, then follow the candle further
The passage is in the typing test with its source and year on the page. Two more come from the same lectures. Why the wick does not burn away is 451 characters, and the shadow of the flame is 460, both easy. If you want the same plain scientific voice from another writer, Darwin on the slowest breeder is 456 characters and spells its numbers out as well.
Longer passages get easier with a routine rather than with effort, and our thirty day plan sets one out. The complete lectures are on Project Gutenberg, and the history of the series is on the Royal Institution site.
