2 Sketch of the latest Improvements [Jan. 



optics, have been studied on the Continent with the greatest atten- 

 tion. I shall take a subsequent opportunity of laying the improve- 

 ments made in these sciences befoie the reader. 



Chemistry. 



This science embraces so vast a field, and is cultivated by so 

 numerous a tribe of votaries, that its annual progress is exceedingly 

 striking and rapid, 1 shall, for the sake of perspicuity, arrange the 

 facts 1 have to state under diH'erent heads ; because 1 consider any 

 arrangement, even though iinperiect, as greatly preferable to no 

 arrangement at all. 



I. General Principles. 



There arc two general principles in chemistry of the utmost im- 

 portance, which have lately attracted a great deal of the attention 

 of chemists, and copcerning which various theories have been started 

 which have had considerable influence on the science. These two 

 principles are, 1. The poiaer by which bodies unite chemically. 

 This power is usually knovvn by the name of afpnlty. 2. The 

 proportions in which bodies unite chemically. The facts established 

 relative to this point have received the name of the atomic theory. 

 I shall endeavour to lay a short view of the opinions relative to these 

 two principles before my readers. 



I. AJjinily. — In the year 1803 an elaborate set of electrical expe- 

 riments on the decomposition of salts and other bodies by the Gal- 

 vanic pile was published by Hisiuger and Bcrzelius.* This paper 

 was republished in ISOG by the authors in the Swedish language. f 

 In 1803 an abstract of this paper was translated from tlie German, 

 and published by the Frencli chemists at Paris. J Among other 

 conclusions from their experiments, the authors draw the following: 

 Substances are decomposed by electricity according to a determinate 

 law. Oxygen and acids are attracted to the positive pole ; while 

 hydrogen, alkalies, earths, and metals, are attracted to the negative 

 pole. This they consider as owing to an affinity subsisting between 

 oxygen, and acids, and positive electricity ; and between hydrogen, 

 alkalies, earths and metals, and negative electricity. This important 

 principle was still further developed by Sir Humphry Davy, and 

 placed in a very luminous point of view in his celebrated lecture 

 On some Chemical Agencies of Electricity, published in the 

 Transactions of the Royal Society for 180S, and which gained the 

 prize proposed by Bonaparte for the most important discovery in 

 galvanism. This dissertation deserves, in every point of view, to 

 be considered as tlie most valuable of all Sir Humphry Davy's phi- 

 losophical discoveries. His subsequent discoveries were more 

 brilliant, and gave him greater eclat ; but ihey were all derived 

 from this profound dissertation, which pointed out the means of 



* Gphlcn's ncties allojemeines Jouinal der Clieinic, i. 116. 

 + Afhandlinsar i F>sik, Kemi ocli Miucralogi, i, 1. 

 ■j AnniUcs de Chiuiie, li, 167, 



