Kent Scientists

Charles Stanhope (1753-1816)

Lived at Chevening, near Sevenoaks

Eccentric aristocrat, scientist, inventor and politician

Charles Stanhope

Charles Stanhope, 3rd Earl Stanhope by Ozias Humphry, 1796 © National Portrait Gallery NPG 380

Chevening House between Sevenoaks and Biggin Hill must be the only stately home in the country whose Great Drawing-Room was once a fully-equipped scientific laboratory. The owner at the time was Charles Stanhope, known first as Lord Mahon and then, following his father’s death in 1786, as the 3rd Earl Stanhope.

Charles was a most unusual man, hugely energetic and with an extremely active and original mind. At a time when it was unheard of for a Peer to be concerned with such matters, he investigated with great vigour over many years a range of problems in which scientific principles were applied to practical issues.

Charles’ father, the 2nd Earl Stanhope, was a distinguished mathematician and used his influence to ensure that his son was elected a Fellow of the Royal Society at the early age of 19. Charles’ own career as scientist and inventor began with a detailed study of electrostatics – the behaviour of electrically charged objects – and in particular of lightning.

An illustration from 'Principles of Electricity' by Charles Mahon (Google books)

Lightning conductors were a subject of debate in scientific circles in the 1770s, amid concern about how to prevent a gunpowder store being accidentally detonated during a thunderstorm, as had once happened in Italy. The controversy was whether a lightning conductor – a metal rod mounted on top of a building and connected down to the ground – should have a sharp point or a rounded end. Benjamin Franklin, over from America at the time, and others, argued that a sharp pointed conductor would be most effective, while another scientist, Benjamin Wilson, maintained vehemently that a round-ended rod below the roofline would be safest. After meeting Franklin, Lord Mahon (as Charles Stanhope was then known) embarked on a lengthy programme of research into the basic principles of electrostatics. His conclusion, in a highly-regarded book published in 1779, was that lightning conductors should indeed be finely tapered with a sharp point, advice which stands to this day and which he put into practice by installing pointed conductors extending seventeen feet above two of the chimney stacks on Chevening House.

Chevening Place

'Chevening Place' in 1830. Two tall lightning conductors can be seen

At times in the 1770s the grounds of Chevening House became the scene of spectacular fires, in one of which flames rose to a height of 87 feet. All were deliberately started by Lord Mahon who was testing new ways to make buildings more fireproof. His method involved sealing rooms to starve any fire of oxygen, and coating surfaces, particularly under the floorboards, with a layer of sand and a special type of mortar of his own devising. For one remarkable demonstration he had a two-storey wooden house constructed in the grounds. The lower floor was filled with wood shavings and other inflammable materials. Ever the showman, he persuaded a number of eminent – and perhaps foolhardy – guests to remain in the upper floor while he ignited the material beneath them. In the inferno that ensued, the downstairs windows were so hot that the glass melted. The gentlemen upstairs however, who included the Lord Mayor of London, the President of the Royal Society, and the former Prime Minister William Pitt, continued to eat ice creams without inconvenience.

A further unplanned test took place 20 years later when a real fire broke out in Chevening House. It spread through several untreated rooms, but halted when it came up against rooms which had been fireproofed. Despite this, the treatment does not seem to have been adopted elsewhere.

The 1790s found Lord Stanhope, as Charles now was, focusing his energies on a new problem, the design of a boat which would be propelled, not by the vagaries of wind and sail but by the reliable application of steam power. To drive his boat he chose to use the ‘duck’s foot’ principle in which a flat paddle mounted beneath the craft would be made to oscillate back and forth. On the backwards strokes the boat would be propelled forwards, but on the forward strokes the paddle would fold to smaller size and cut through the water without appreciably slowing the boat.

Chevening House today, showing part of the lake where Stanhope tested his 'ambi-navigator'.

Early trials on the lake at Chevening seem to have been promising, even though the unorthodox method of propulsion only worked when the boat was already in motion. To start it from scratch a towrope was attached pulled by a gang of Chevening gardeners, presumably on dry land on the other side of the water. In his enthusiasm, Stanhope would unexpectedly cut the rope once the boat was moving, unmindful that this caused the towing team to fall flat on the ground.

Another feature of Stanhope’s design was that his boats were pointed at both ends. By adjusting the underwater paddle they could be made to move equally well in either direction. He therefore called them his ‘ambi-navigators’.

Stanhope’s attempts to convince the British Navy that steam powered warships were the future met with a cool response. But the officials did agree that if he built a larger trial boat and it worked they would reimburse the cost. Stanhope went ahead with commissioning a 200 ton ambi-navigator, the ‘Kent’, from Deptford Dockyard.  Fifty-five feet in length and 6 feet wide, it was propelled by six duck’s-feet paddles, three on each side. Adapting a steam engine to move paddles required all its inventor’s ingenuity since the only steam power available at that time came from huge beam engines. Eventually a compact 12 HP engine was built and installed and trials of the Kent began in the Thames near Rotherhithe.

When it transpired that the boat’s top speed was only three miles per hour the Navy withdrew its support, and the Kent was scrapped soon after. But Stanhope’s experiment may have inspired others to try different methods of propulsion. When the first really practical steamship took to the water in Scotland in 1803 it was a paddle-steamer.

Among Stanhope’s other inventions were two mechanical calculators, the second of which could multiply or divide 12-digit numbers faultlessly by turning a handle. Machines on similar principles remained in common use in science and commerce until the advent of electronic calculators two centuries later. A long-term interest in the principles of logic led to the creation of a device called the Stanhope Demonstrator, capable of solving simple logical problems. Fed with the information, for example, that out of a group of 10 cats, 8 have a white tail, and 4 have one white paw, the Demonstrator would correctly show that the number of cats with both attributes must be at least 2. Stanhope’s calculators and demonstrator are now in the Science Museum in London.

A 'Stanhope' iron printing press

Concern that printed material should be produced more efficiently, and so be affordable by as many people as possible, led him to introduce a number of innovations in the art of printing. The best known of these is the Stanhope Press. For three centuries from the time of Gutenberg, the hand press had changed little. In particular the force that pressed the paper down onto the inked type was still applied by means of a screw mechanism. Stanhope added a system of levers that would do the job much more effectively, which meant that a sheet of paper could be printed with a single pull of the press, rather than two pulls as previously. At the same time, he redesigned the hand-press, which until than had always been made of wood, with a massive cast iron frame. Soon book printers and newspaper proprietors were throwing out their old wooden presses and installing Stanhope iron ones – manufactured by a number of different firms since the Earl, on principle, did not take out a patent on his invention.

In parallel with his work as scientist and inventor Charles Stanhope pursued an equally active career as a maverick politician, first in the House of Commons, and then in the Lords where he often found himself in a ‘minority of one’. Deserted by his family in later life, he led an ascetic life at Chevening, reportedly sleeping under 12 blankets with the windows open even in the coldest weather. On his death in 1816 Chevening was described as ‘a dilapidated and decayed house standing in a hayfield’. (Today it is the official residence of a senior government minister.)

Charles, 3rd Earl Stanhope is buried in Chevening Church, where a simple tablet reflects his own request to be buried ‘as a very poor man’.