260 Instrument for determining Speeijic Gravities. 

 Table II. 



In preparing these springs, care was taken to keep the dif- 

 ferent coils of each a little asunder; they would not stretch 

 uniformly if allowed to be in contact any where. 



The space through which a given weight stretches any of 

 these springs is in proportion to the number of coils contained 

 in it, the diameter being the same ; but where the diameters are 

 various, there does not appear to be any regular proportion, 

 though in some cases it was observed to be nearly as the 

 squares of these diameters ; the tables, however, may assist in 

 giving a general idea of the size of .springs required for any 

 given weight, and in an instrument to be used for weighing or 

 taking specific gravities, as above described, two or three 

 springs might be contained, suited to different weights and di- 

 vided scales of ounces, grains, &c., added to make it useful 

 as a common spring balance ; a very small box or case would 

 contain the whole, and the scale of diverging lines may be put 

 inside the lid or cover. 



I have the honour to be. Sir, 



Your very obedient Servant, 



Henhy Creigiiton. 

 W. T. Brande, Escj. R. I. 



