226 Dr Davy's Observations on Fish, 



muscle and fat, to whatever class belonging, is approximately 

 denoted by their several specific gravities, and by the amount 

 of solid matter which each contains, as determined by tho- 

 rough drying, or the expulsion of the aqueous part at a tem- 

 perature such as that of boiling water, not sufficiently high 

 to effect any well-marked chemical change. 



In the trials I have made, founded on this proposition, the 

 specific gravity has been ascertained in the ordinary hydro- 

 statical w r ay ; — the portions subjected to trial, in the instance 

 of fish, have been taken from the thicker part of the back, 

 freed from skin and bone, composed chiefly of muscle. And 

 the same or similar portions have been used for the purpose 

 of determining their solid contents, dried in platina or glass 

 capsules of known weight, and exposed to the process of dry- 

 ing till they ceased to diminish in weight. 



The trials on the other articles of diet, made for the sake 

 of comparison, both as regards specific gravity (excepting 

 the liquids), and the abstraction of the hygroscopic water, or 

 water capable of being dissipated by the degree of tempera- 

 ture mentioned, have been conducted in a similar manner. 



The balance used was one of great delicacy, at home, or a 

 small portable one, when from home, of less delicacy, yet 

 turning readily with one-tenth of a grain. 



The results obtained are given in the following tables. In 

 the first, on some different species of fish ; in the second, on 

 some other articles of animal food. 



I have thought it right, whenever it was in my power, to 

 notice not only the time when the fish were taken, but also 

 the place where they were procured, — not always so precise 

 as I could wish, — as both season and locality may have an 

 influence on their quality individually. When the place men- 

 tioned is inland, it must be understood that, in the instance 

 of sea-fish, they were from the nearest sea-port. 



