300 Records of Measures 



The circumference was measured by a slip of tinfoil put round, and the 

 intersection marked with knife. 



The substance of glass was found by hanging it to end of sliding ruler 

 fastened to one end of balance, and weighing it in water; and by sliding the 

 ruler I made more or less of it to be immersed, and knew the difference of the 

 space immersed. 



M. ii. Specific gravity of different pieces of white glass. 



The small jar being broke, a 2 nd was measured. 



Thickness measured by calipers in 4 different rows parallel to axis and in 

 5 different places in each row, beginning at a scratch with a file near bottom. 



[Here follow the measures.] 



The thickness was then tried in 4 different parts of circumference at 4-4 inc. 

 distance from scratch. 



It was then weighed in water in the same manner as the others. 



The jar was dried before each trial, and before the 3 rd was rubbed with 

 solut. p. ash*, which made the water stick less to side, for which reason it is 

 supposed most exact. 



The circumference was measured in two parts of the middle space, and 

 they came out both the same. 



595] M. 12. Measures of coatings to jars and cylind.] 



A coating made to 2 nd small jar extending to 4-4 inqhes from scratch. Comp. 

 power = 680-7. 



Coating to white cylinder extends 9-86 inches from double mark. Comp. 

 power = 684-1. 



A coating made to 4 th green cyl. extending 7 inches from mark. Comp. 

 power = 318-2. 



A mark was made on wide part, extending 7-16 inc. from new mark. Comp. 

 power 600-7. 



M. 13. A mark made on 2 nd green cylinder 11 inches from first towards 

 thick end, and the tube cut off about i inch from I st mark. 



A coating made to the thick part extending 8-55 inches from 2 nd mark. 

 Comp. power = 600. 



* [Pearl ash.] 



f [See Art. 383. The computed power here is 8 times the true value, and there 

 is no correction for spreading of electricity.] 



