20 The Progress of Physical Discovery. \_ J ANV 



remedy this inconvenience ; and the calorimeter now in use was Invented 

 by the latter. These researches on capacity led to the recognition, by 

 Lavoisier and Delaplace, of the combination of heat with bodies, in an 

 elastic or gaseous state, which is reproduced with violence, when the 

 combination is separated, as is the case with the explosion of gunpowder. 

 The modification of chemical affinities by heat, and the degree of 

 influence of pressure in such modifications, have occupied the attention 

 of Sir James Hall, of Lavoisier, Dalton, and Watt ; and the employ- 

 ment of steam as a moving force, has formed a new eera in society, and 

 is one of the most striking proofs that can be adduced of the influence 

 of science upon the prosperity of nations. 



The production, transmission, and chemical action of electricity have 

 been the studies of Cavendish and Wollaston names that will long live 

 in the annals of English chemistry as well as of Pfaff and Van Marum. 

 Its production, by the contact of bodies, called Galvanism, has perhaps 

 excited more curiosity than any other branch of physics, whether con- 

 sidered in its effect upon the animal economy, as first developed by Gal- 

 vani ; in its nature and origin, as demonstrated by Volta ; or in its 

 peculiar chemical action, recognized by Rutter, Carlisle, Davy, and 

 Kicholson. The experiments of Sir Humphrey Davy, in particular, 

 ascertained in 1807, that acids combine with alkalis and metallic oxides, 

 in consequence of their being in opposite states of electricity; from 

 which results the important truth, that the simple contact of heteroge- 

 neous substances has the power of altering the electric equilibrium, and 

 that this alteration may extend to the chemical affinities of all surround- 

 ing bodies. Our illustrious countrymen seems by this discovery to 

 have opened a new source of light in natural philosophy, for it is easy 

 to perceive the great influence of this tranquil and continued action upon 

 the surface and interior of the globe, and perhaps upon the complicated 

 movements of life. 



The theory of combustion, so important in its application to the arts, 

 and the uses of domestic life, as well as in its influence over the pheno- 

 mena of nature, was unknown to the ages preceding our own. It was 

 within the period of the present generation that the discovery of latent 

 heat, by Black; that of the disengagement of air from the ashes of 

 mercury, reduced without attrition, by Bayen ; and that of the produc- 

 tion of fixed air in the combustion of carbon, and of water in that of 

 inflammable air, by Cavendish, formed the ingredients from which 

 Lavoisier had the glory of ascertaining the true nature of combustion in 

 general. It was from him that we learned, in 1774, that all combustible 

 bodies absorb, in burning, only that portion of air that is pure or 

 breathable, and that, in a quantity precisely equal to the augmentation 

 of the weight of the alkalis or acids produced, they emit this air in 

 reducing themselves, and that the air returned is changed into fixed air 

 when they are reduced by carbon. Upon this was founded the new 

 system called French Chemistry, which was proclaimed not only by 

 Lavoisier himself, but by Fourcroy, Berthollet, and Guyton, and the 

 other distinguished men who, discarding all rivalry and jealousy, ranged 

 themselves at once under his banners, and promulgated hisr principles in 

 their works and their lecture rooms, in a way as honourable to them- 

 selves as to the annals of science. The French theory, which is now 

 almost universally received, was endeavoured to be modified by Winterl, 

 of Pesth, in 1800, who asserted the existence of two principles of acidity 



