1820.] Physical Science during the Year 1819. 3 



matter exactly similar to the sugar of grapes. The same sugar 

 makes its appearance in barley when it is malted ; but hitherto 

 it has been out of our power to explain any of these complicated 

 processes, or to show how any of these changes is induced. 



But notwithstanding the imperfection of our present know- 

 ledge, I see no reason why we should despair of being able 

 hereafter to account for many of those processes which puzzle us 

 at present, and even of being able to form artificially various 

 substances, both animal and vegetable, which we cannot do at 

 present. The first thing is to determine with accuracy the sub- 

 stances of which these bodies are composed ; and the next to 

 make ourselves acquainted with the laws by which the combina- 

 tions of these bodies are regulated. 



The great number of distinguished individuals at present 

 devoted to the study of chemistry, and the very considerable 

 progress which it annually makes, renders it more and more 

 probable every year that these hopes will be ultimately realized. 

 My object in this paper is to give a view of the progress which 

 our science has made, or rather of the new chemical facts which 

 have come to my knowledge, since the last annual historical 

 sketch was drawn up. I do not know how far these annual 

 views may interest or inform the reader ; but I never fail myself 

 to add to my own knowledge while engaged in drawing them up. 

 The very necessity of classifying the facts, and of comparing 

 them with each other, serves materially to make them sink deep 

 into the memory ; while they often suggest new experiments and 

 new views which I am afterwards led to prosecute with consider- 

 able advantage. I shall as usual arrange the facts which 1 have 

 to mention under distinct heads, without being very solicitous 

 about minute precision of arrangement. 



I. Apparatus, 



A good treatise on chemical apparatus, and on the mode of 

 conducting chemical experiments, is at present a desideratum in 

 this country. I have been making arrangements for some time 

 to endeavour to supply this defect, and hope before many years 

 elapse to publish a treatise on the subject, which will be of some 

 utility to practical chemists. I conceive it to be requisite that 

 such a book should contain little except what has been actually 

 verified by the author. This of necessity renders it a work 

 which can proceed only from one who has been for a number of 

 years actually engaged in chemical investigations. 



1. The only piece of apparatus which 1 consider it necessary 

 to notice here is the one contrived by Dr. Prout for analyzing 

 organized bodies by heating them with peroxide of copper. It 

 is described, and a figure of it given in the Annals of Philosophy/, 

 vol. XV. p. 190. This apparatus is in itself so simple, while it is 

 80 distinctly described in the paper which accompanies the 

 engravings, that it is only necessary to refer the reader to the 



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