338 Dr. Thomson's Observations on the Weights of [Nov. 



been proposed as a prize question, to discover the substance 

 which in potatoes supplies the place of sugar, to which alone the 

 spirituous fermentation is conceived to belong. A set of experi- 

 ments on potatoe meal, obtained by rasping, washing, drying, 

 and grinding, has shown that these bulbs contain sugar and 

 gum in the proportion of 64 gr. of mucous sugar, and of 220 gr. 

 of gum, in the pound weight of potatoe. These two principles 

 were discovered by digesting potatoe meal in six or eight parts 

 of cold water for 24 hours in a cool place, evaporating the 

 water to dryness, and treating the residual mass successively 

 with alcohol and water. Now it is the existence of these two 

 principles which occasions the commencement of the spirituous 

 fermentation, assisted by the barley meal. Their action upon 

 the starch, and the changes induced in it, account for the quan- 

 tity of spirit produced. 



These two discoveries, my Lord, have a real connexion with 

 political economy ; and tney interest the sciences, as they consti- 

 tute incontestible matters of fact. I may have the honour 

 hereafter of transmitting an extract of the memoir which my 

 brother proposes to read at the annual meeting of the Helvetic 

 Natural History Society, on the tribe of corns and their 

 products. 



Our means of public education will be considerably improved 

 by the choice which has been made of a very convenient place 

 for experimental lectures on chemistry, physics, astronomy, &c. 

 by the association of about 200 persons connected with the 

 same place, who receive all the scientific journals of the world, 

 and who invite foreigners of every description for the election of 

 new professional chairs, and even of new faculties of science 

 and literature. Our academy will see with pleasure foreigners 

 in its bosom (provided they be distinguished by their knowledge) 

 reading public lectures on the sciences, and thus adding to the 

 scientific resources of Geneva. We are at present purchasing 

 in Paris a great many physical and astronomical instruments, 

 which were wanting for our lectures. Already we have begun 

 to form a cabinet of natural history, mineralogy, &c. The place 

 is very large ; and we are receiving from all quarters objects 

 worthy of a place in this interesting museum. 



Peschier, D.M. 



Article III. 



Some Additional Observations on the Weights of the Atoms of 

 Chemical Bodies. By Thomas Thomson, M.D. F.R.S. 

 Regius Professor of Chemistry in the University of Glasgow. 



Though little more than five years have elapsed since I pub- 

 lished my first tables of the weights of the atoms of different 



