PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 931 



vanometer, and note the deflection which the battery gives. I 

 then insei't some known resistance (r'), say a wire or coil of 0.2 

 miles, and note the rednced deflection. The tangents of these two 

 deflections give s and s'. We have, then, the known qnantities 7*', 

 s, and s' from which, by the formula, we compute ?•, the interior 

 resistance. The results obtained by the two methods agree almost 

 perfectly. 



For compound battery, I use the intensity galvanometer, and 

 insert some larger known resistance (r), as a mile, or ten miles; 

 or more, according to the length of the series. Let the resistance 

 of the galvanometer coil be represented by y, and the formula 

 will be, 



e e 



= s, and = s' 



(/ -}-r gf -^r + r' 



in which (/, i'\ ,9, and s' are known quantities. 



The interior resistance of the nitric acid and chromic acid batter- 

 ies, under difierent circumstances, I have found as follows, the cir- 

 cuit being kept closed on a local sounder, which gives 0.3 mile 

 resistance: One cup Grove's battery (new), r = 0.047 mile; same 

 after running 8 hours, r = 0.068 mile; same after running 16 

 hours, r == 0.140 mile; one cup chromic a(;id battery (new), r = 

 0.027 mile; same at 6 hours, ?• = 0.062 mile; same at 16 hours 

 (about run down), r = 0.154 mile. With Hill's battery,?- ranges 

 from one to two-tenths mile, according to the size and proportions 

 of the cup, at all times. The resistance of the same cup scarcely 

 varies two hundredths of a mile from month to month. 



The r is a very good index to the constancy and durability of 

 the several batteries. 



The following paper was read by the translator: 



The Cotton Seed Oil. 

 Its Physical and Chemical Properties. 



[Translated from Jacobson's Repertorium by Dr. Adolf Ott.] 



If cotton seed is pounded and then heated to 167° to 181° F., it 

 yields, by pressing, 15 to 18 i)er cent of a dark brown colored 

 oil, containing more or less slime and albumen in suspension and, 

 perhaps, a portion in solution. It is 28 to 30 times less liquid 

 than water, and its ^specific gravity is not always the same. Adri- 

 ani found it to be 0.93074 at 53.5° F., from a middle proof of 24 

 barrels; another proof he found to have the specific gravity of 



