Photograph: David Remes (2003)

A rough sketch from 1779 can be understood as a rocket motor powered by compressed hydrogen and oxygen (inflammable air and dephlogisticated air in Darwin’s terminology) as propellants. The gases are stored in separate containers and fed into a cylindrical chamber with an exit nozzle at one end. The volume of hydrogen is correctly shown as being greater than of oxygen. Darwin’s idea appears to be very advanced for his time, as the invention of hydrogen-oxygen rocket has been usually associated with Konstantine Tsiolkovskii (1857-1935). It came into use for space launches from the late 1960s.

Photograph: David Remes (2003)

Some of Darwin’s inventions were inspired by his medical practice. He experimented with various therapeutic methods including electrotherapy, which was coming into fashion in the late 18th century. For electrical treatment he needed a special generating machine. Among his designs of 1778 is an ‘electrical doubler’ which was quite successful and became well known at that time. Darwin’s friend Abraham Bennet (1750-1799) to whom Darwin passed his improvements, later described Darwin’s work in the following way:

Dr Darwin made the first attempt with two plates mowing between two others by a lever, so as to bring them exactly to the same position in each operation. This contrivance he soon improved by another instrument in which the plates stood vertically and moved by rack work in a direction exactly parallel to each other.

Photograph: David Remes (2003)

In 1778-79 Darwin continued his work on a copying machine and perfected a ‘polygrapher’ – a model working on the pantograph principle. It was able to duplicate writing and drawings, and produced an identical copy. In this variant the pen was not stiffened, and the height of the machine was reduced.

Photograph: David Remes (2003)

Many of Joseph Priestley’s experiments with air of the mid 1770s were discussed at Lunar meetings, and Darwin’s Commonplace book reflects his interest in them:

There is a reason to believe from some of Dr Priestley’s experiments that air which has been breathed, by being washed in water becomes fit to breath again. Suppose a person was to put his head under a small diving bell, & by such a pump, as that described on the reverse page, could throw a stream continually in showers about the bell, would it not sufficiently purify the air? The water should be a running stream, & the pump takes it from a little distance. It might not be the same water again & again. This experiment with a candle & a syphon inverted under a cork might be easily tried.

Photograph: David Remes (2003)

In 1760s, Darwin was deeply involved in a major enterprise – the building of the Grand Trunk Canal. This inspired him with the idea of a canal lift, which is described in an entry in the Commonplace Book dated 1777-1778.

If a canal has to climb a hill, a number of locks is usually needed. These will delay traffic, or may be difficult to build. They also allow water to escape from the upper stretches of the canal whenever a boat passes. Darwin’s lift for was intended to avoid these difficulties, and also to link the canal with a river below. He proposed raising and lowering the boats in two water-filled wooden boxes suspended on chains, each acting as counterweight to the other.

Let a wooden box be constructed so large as to receive a loaded boat. Let the box be join’d [to] the end of the upper canal and then the boat be admitted, and the doors of the admission secured again. Then the box with the boat in it being balanced on wheels, or levers, is let down, and becomes a part of the inferior lock.

Since then many lifts of a very similar design to Darwin’s invention have been installed on British canals – including the Grand Trunk Canal with which Darwin was directly associated.

Photograph: David Remes (2003)

Sketches of a mechanical copying machine, or ‘bigrapher’, from 1777. The writing is done with the quill on the extreme right of a 3 ft long arm. The tube near its middle duplicates the document on a separate sheet of paper at the same time as it is written.
Today a working model of the bigrapher can be seen and tried out at Erasmus Darwin House, Lichfield. Darwin would later work on another type of copying machine.

Photograph: David Remes (2003)

Darwin’s drawing of 1777 represents an artificial bird (a goose) with flapping wings

Let a watch-spring be fix[ed] with one end to the frame & the other wrap’d round an axis; at each end of the axis let a wheel be put with teeth of such form & situation that they shall move a wing, like a bat’s wing, or like a ladies fan, one tooth carrying it downwards, another carrying it towards the body, another carrying it upwards, & a fourth outwards again from the body. NB. One edge of the wing is to be fasten’d to the body & the other to a kind of fan-stick made of a porcupine quill. The tail of feathers spread out & lying obliquely to the action of the wings, or rather to its intended track in the air.

At first a small gunpowder motor was suggested as the in-flight rewinding mechanism, but later Darwin replaced it with a reservoir of compressed air.

Although the idea of a mechanical bird was by no means new, even towards the end of the 18th century there was still no satisfactory explanation of the mechanics of flight. Darwin’s description of a bird’s flight is very close to reality, and appears to be the first complete account of a power-plant and the necessary cycle of the wings’ movement.

Image: Title page of Erasmus Darwin’s Commonplace Book

Photograph: David Remes (2003)

One of the most significant original objects reflecting Erasmus Darwin’s life and work is his Commonplace Book. It now belongs to English Heritage, and can be seen at Erasmus Darwin House, Lichfield.

It is a quarto volume, lavishly bound in vellum and containing about 300 sheets of fine paper. It was produced by the well-known London printer, publisher and bookseller John Bell (1745-1831). The title runs as follows: ‘Bell’s Common-Place Book, Formed generally upon the Principles Recommended and Practised by Mr Locke. London. Printed for John Bell, near Exeter Exchange in the Strand.1770’. Each line of the title is printed in a different typeface, as if to indicate the variety of individual characters which can be reflected in a commonplace book. By publishing a finely bound book of blank pages, Bell invited his customers to participate in the culture of letters, both as readers and writers. On the first pages, hints are provided on how to use a Commonplace Book. A few lined pages follow, with inserted letters for an alphabetical index. There are 136 entries in Erasmus Darwin’s own handwriting in the index pages.

Blank pages 1 to 160 are numbered and filled by Erasmus Darwin. He started this book in 1776 and continued it until 1787. Darwin’s records in the Commonplace Book do not refer to his experiments before 1776, although some material has been transferred from another source. Presumably there must have been at least one earlier Commonplace book, which has not been found.

On the first pages there are mostly medical records, but gradually the proportion of notes and drawings on other subject increases. These clearly reflect his thoughts on various scientific matters, mechanical and industrial improvements, and inventions for both public and domestic use. Some of them were successfully put into practice, some came to nothing; and some were reinvented later by others.

After his death in 1802 the book presumably passed to his widow Elizabeth who added some details of family history. Then the book passed to her son and his descendants. In their turn they added a few entries, mostly of a family character. Finally, Leonard Darwin (1850-1943), the last surviving son of Charles Darwin, gave it to Down House, Kent. In 1999 the Commonplace Book was loaned to Erasmus Darwin House, Lichfield.

Erasmus Darwin’s Commonplace Book is not only a valuable source of information on 18th century science and medicine, but also a unique and precious document revealing the fertility of creative imagination and the variety of talents of one of the most inventive and influential characters of the Industrial Revolution and the Age of Enlightenment.