490 
PROFESSOR SCHUMACHER ON THE LATE 
for brass), and of whose specific gravity, even if we assume it of brass, we are equally 
ignorant. 
We will previously state the following results of the weighings given in ^ 19. in a 
form adapted for the subsequent calculations. 
m. 
log b. 
t. 
A. 
log 
° A 
C. 
g r - 
K = 5760-03389 
1-47197 
65-09 
7-994 
+ 0-00033 
S.p = 5759-99143 
1-47308 
05-62 
21-1874 
8-67392 
S. b = 5759-98966 
1-47661 
64-50 
8-228 
— 0-01220 
RS = 5759-99795 
1-47430 
65-73 
21-1874 
8-67392 
RM = 5760-00887 
1-47245 
65-91 
7-994 
+ 0-00033 
The column marked with A contains the specific gravities of the pounds compared 
with U. Of these, the specific gravities of K and S.p only have been found by weigh - 
ing in water*. The specific gravity of S. b is the mean of the specific gravities of two 
other brass weights made by Mr. Robinson, supposing that his brass was always 
nearly of the same specific gravity, which is indeed a precarious supposition, but 
may be adopted until S. b itself be weighed in water. The specific gravities of RS 
and RM are unknown. I have, until they be determined, supposed RS of the same 
specific gravity with S.p, and RM of the same specific gravity with K. Indeed K 
and RM are both made by Mr. Bate, and probably at the same time, so that it seems 
allowable to suppose that they are of the same metal. 
The column c contains the correction for the three brass pounds to be applied to 
the log a found in Table I., on account of their specific gravities differing from 8*0, 
which is the specific gravity supposed in Table I. This correction is = 0*90309 — 
log l (see § 29.). 
33. We may now calculate the reduction to a vacuum for these weighings, on two 
hypotheses ; assuming U, 
1°. to have been of brass, with the specific gravity = 8*0 ; 
2°. to have been of copper, with the specific gravity = 8*788. 
• • • 7 ^ 
In the first hypothesis, the logarithm of the quantity (3 y = a, may for U be taken 
R 3 
immediately out of Table I. Likewise the log of the quantity (3 — may for the 
three brass pounds be taken out of Table I., on applying to the log a t>he correction c, 
R3 
stated at the bottom of that Table. For the two platina pounds, (3 y must be cal- 
culated separately, which is also the case with (3 y if we assume U to have been of 
copper. Log (3 is taken out of Table II. 
* S.p itself has not yet been weighed in water. Its specific gravity is determined by weighing in water an- 
other weight of the same platina, which Mr. Robinson made for me, for that purpose. 
