He observed that the force of the charge was always sensibly increased when the gun was discharged by firing a pistol (constructed for that use) into the vent, instead of using a priming and a common match for firing off the gun.
These experiments were continued in 1792, and in 1793 they were shown to Dr. Blagden, who was in Munich during the absence of Sir B. Thompson in Italy for his health.
The principal objects in view were to determine the expansive force of the elastic vapour generated in the combustion of gunpowder in its various states of condensation, and to ascertain the ratio of its elasticity to its density, and to measure the utmost force of this fluid in its most dense state.
In order to find the most economical method of lighting his Workhouse at Munich, he devised a new way of measuring the relative quantities of lights by their shadows. His arbitrary standard was a London made Argand lamp. He first experimented on the resistance of air to light, then on the loss of light in its passage through different kinds of glass, and in its reflection from a plate glass mirror, then on the relative quantities of oil burnt by different lamps and relative quantities of light emitted by different substances, and lastly on the transparency of flame.
He made these experiments into a paper on the ‘Relative Intensities of the Light Emitted by Luminous Bodies,’ and it was read before the Royal Society, February 6, 1794; and on February 20 another paper was read, being an ‘Account of some Experiments on Coloured Shadows,’ and he came to the conclusion that our eyes are not always to be believed, even with respect to the presence or absence of colours.
For his national and scientific work he received various honours between 1783 and 1794.
In 1785 he was elected member of the Bavarian Academy of Sciences, which had been established in 1758, and he was made chamberlain to the Elector.
In 1786 the King of Poland, at the request of the Elector of Bavaria, conferred on him the Order of St. Stanislaus. This was done because the statutes of Bavaria did not allow a foreigner to receive any national honours.
In 1787, when in Prussia, he was made a member of the Berlin Academy of Sciences.