249 



otlu-r riiiise* which hare appeared to him t(t contribute to the sus- 

 tained action of his battery, he has reniarixed, that considerable ad- 

 vantage seems to arise from the occasional exposure of the plates 

 to the air. 



The voltameter of the author consists of a tube bent like the let- 

 ter U, which at one end has a glass reservoir attached to it, of the 

 same capacity with the tube, and at the other graduated end has a 

 stopcock to allow the gas to escape upon occasion, which accumu- 

 lates at that end from the platinum wires evolving the gases at the 

 bottom. 



2. Notice upon the Alcoholic Strength of Wines. By Dr 

 Christison. 



Various accounts have been given of the alcoholic strength of 

 wines by Mr Brande, Julia-Fontenelle, and others. The author 

 has been engaged for some time in experiments for determining 

 the proportion of alcohol contained in various wines of commerce 

 and also the circumstances which occasion a variety in this respect. 

 The present paper is an interim notice of the results. 



The method of analysis consisted in the mode by distillation, 

 which was applied with such contrivances for accuracy that nearly 

 the wlude spirit and water were distilled over without a trace of 

 empyreuma, and without the loss of more than between 2 and 6 

 grains in 2000. From the quantity and density of the spirit, the 

 weight of absolute alcohol of the density 793.9, as well as the volume 

 of proof spirit of the density 920, was calculated from the tables of 

 Richter founded on those of Gilpin. 



The author has been led to the general conclusion that the al- 

 coholic strength of many wines has been overrated by some expe- 

 rimentalists, and gives the following table as the result of the in- 

 vestigations he has hitherto conducted. The first column gives the 

 per-centage of absolute alcohol by weight in the wine, the second 

 the per-centage of proof spirit by volume. 



Alc. p. c. P. Sp. p. c. 



by weight, by volume. 



Port— Weakest 1497 30 gg 



Mean of 7 wines, ...... 16'.20 3391 



Strongest, 17.10 37.27 



White Port, 14.97 31.31 



Sherry— Weakest, 13.98 30.84 



Mean of 13 wines, excluding those very long 



kept in cask, 1 6.37 3359 



