262 



Dr. Andrew Steel 



[April 



spirit, we add water, till the bulk is exactly 100 measures, 

 such a mixture, in the language of Sikes, will be 50 per 

 cent, under proof. The term per centage, is in one sense, 

 therefore obviously defective, since spirit for example of 

 50 per cent, under proof, is not composed of 50 of spirit 

 •+■ 50 water, but of 50 spirit + 51 of water. 



Knowing the composition of proof spirits, we can easily 

 calculate the per centage in these terms, of that at any 

 other specific gravity, and the correspondence of the indi- 

 cation of the instrument with this, will be a proof of its 

 accuracy, and vice versa. 



The rule for this calculation may be represented generally, 

 as follows : 



Let s=the specific gravity of the liquid under tried. 

 ,, c=its per centage of alcohol. 



,, #=the proof spirit it contains per cent, or is capable 

 of producing. 



,, y=the per centage, in the language of Sikes' tables, 

 2-0325203. S .c. =2 . 21029jsc = ;c _ 



X = - 



■91957 



and y= iqq°£ as the spirit is over or under proof. 



Thus, in the case of proof itself, we have 



s = 91957, and c = 49*2, consequently, 

 x = 2-21029 x -91957 x 49-2 = 99.999, and 

 y = in this case to 0* 

 The following table exhibits the correspondence between 

 Sikes' Hydrometer, and the per centage calculated from the 

 specific gravity by the above rule. 



