452 O. N. Rood—Application of the Horizontal Pendulum to the 
Determinations of the value of a scale division. 
In No. 1, after using the micrometer-screw, five readings were 
taken consecutively, the interval between them being only that 
required for making the record; in Nos. 2 an single readings 
only were taken, but each reading is to be regarded as a mental 
average of at least two or three readings; in No. 4 twenty- ae 
consecutive readings were taken on each occasion. The 
mode, on the whole, seems to be to take in each case not ‘ae 
than five or more than ten rapid readings, and then again to 
use the micrometer-screw. 
No. 1. 
Actual readings. Average. Difference. 
54°2 53°2 53° 53°4 27°8 
81°5 80°9 81°6 80°8 81°2 27°8 
53°5 55° 53°4 53° 52 53°4 29°2 
83° 82°3 83° 83° 82 82°6 29°0 
56°3 54°2 54° 51°6 52 6 28°1 
S2 -8I°° 83" < 83 81°5 81°7 29°6 
53°2 52°7 51° 53°5 50°2 52°1 29°4 
80°3 81°3 82°8 82° 81:2 81°5 28°2 
Although in these observations the temperature seems to 
have been constant, yet for the sake of uniformity I have pre- 
ferred to treat them ‘according to the method above described. 
M’ MM”, 
27°8 28°5 28°15 
29°1 28°5 28°80 
28°8 29°5 29°15 
Final average, 28°7 
The probable error is 0198 of one scale division; which, 
with the adjustment then employed, corresponds to TT,300,000 
of an English inch. 
No, 2 
Actual readings: ': — Ditt Mw’. Mw”. M. 
a -, 28 28°25 28°12 
mee ie 29°5 30°25 29°87 
ra: ee 31°75 30°25 31° 
ite ae 26°75 26° 26°37 
ace are 27° 27°9 27°45 
BE anes tes 
24°3 29°9 Final average, 28°48 
