42 REPORT—1904. 
material support to the station of Shide ; his brother, Mr. R. K. Gray, 
provided the instrument for San Fernando ; Mr. Joseph Wharton, of 
Philadelphia, U.S.A., gave the instrument installed at Strathmore Qol- 
lege, near that city ; ‘pendulum apparatus was given to Shide by Mr. 
A. F. Yarrow ; the instruments in Hawaii, Victoria, and Mauritius were 
paid for, or partially paid for, by funds put at the disposal of your Secre- 
tary ; while the remaining installations were established by institutions or 
Governments in the countries where they are now working. 
II. On the Comparison of Records from three Milne Horizontal 
Pendulums at Shide. 
These pendulums and their installations referred to in the following 
note are described in the British Association Reports, 1902, p. 60, and 
1903, p. 81. 
Pendulum A is the type instrument, and carries a load of 243 gms. 
It stands on its own pier, records E.W. motion, and its period, like 
similar instruments in other parts of the world, has been kept at about 
seventeen seconds. 
Pendulums B and C stand on the same pier and swing on the same 
cast-iron upright. JB is parallel to A, and, like it, records E.W. motion. 
C responds to N.S. motion, but by means of an arm attached to it, 
similar to the arrangement shown in the British Association Reports for 
1902, p. 61, fig. 1, its records are made side by side with those of B. 
At intervals of several months the loads carried by B and C have been 
purposely varied, and the object of this note is to show the differences in 
the results obtained in consequence of such changes. In considering these 
differences two points not to be overlooked are, first, that only the move- 
ments of A and B are comparable ; and secondly, that the swinging of B 
might.cause motion in C, and wice versa. 
The comparisons given in the following table refer to the number of 
records given during different periods by A, B, and C, and the number of 
| 
—--- | Number of Records Number of Early 
Commencements 
December 28, 1902, to April 28, 1903 | 
A B C A B Cc 
fe Deslas W. 243 grms. 5 = = 
TB, pelt, We2os - 5, : ; 35 35 31 15 12 15 
|G, p. 20, W. 155, J ate ‘ 
April 28 to December 6, 1903 
A, p. 17, W. 243 grms. . - | = = 
iB; pili We23t 4 5; : : “29 40 50 9 12 47 
” 
C, p. 20, W. 404 ae be 
December 8, 1903, to May 2, 1904 | 
(A, p. 17, W. 243 grms. _,, | 22 40 al 8 
foeee poo ese 2 
| C, p. 20, W. 404, ; i a | 
27 
[le 
times each of these pendulums commenced to record either sooner than the 
others or at least simultaneously with one of the others. P=period in 
seconds, and W=load carried by the booms expressed in grammes, 
