184 REPORT—1896. 
We do not know which instrument would at a given station commence 
to move the first. The probable order would be R, M, D, V. 
Carts, trains and traffic, unless very near, do not affect any of the 
instruments. 
D and V are probably not affected by ‘earth (?) tremors’ whilst 
M and B& are aifected, but the serious character of these in obliterating 
effects due to small movements has been greatly reduced. 
D and K are most sensible to tilting effects hke the diurnal wave, and 
therefore, unless we reduce their multiplication by reducing the distance 
between the mirrors and the film, they require a broad recording surface. 
D is entirely unaffected by rapid tremors. The movement of the 
image during the passage of earthquake pulsations is absolutely steady, 
showing that the rapid vibrations superposed on the long waves (tiltings of 
the ground) are entirely quenched. 
Installation and working.—V requires a strong support, like a solid 
wall, and vertically a space of 10 or 12 feet. 
Rand D require, as at present used, at Jeast 12 feet horizontally, and 
unless we reduce their multiplication, a fairly strong light, and consider- 
able isolation from the effect of loads. Six feet might be ample for R and 
D. The foundation for D costs 7/. or 81. 
M requires 4 feet horizontally, a small light, and moderate isolation. 
Each instrument will require about ten minutes’ time daily, and about 
one hour each week. 
It is possible that the smoking and varnishing of a long roll of paper, 
as required by V, may be more troublesome than developing the photo- 
graphic films of M, R, and D. The M film lasts one week. Rand D 
require changing at shorter intervals. 
Cost.—V, as made in Italy, about 20/., but without timekeeper. 
M, as made in England, 45/. with timekeeper. 
R, as made in Strassburg, about 297. without special timekeeper. 
D, as made in England, about 50/. without special timekeeper. 
Mr. Milne suggests to the Committee that they should buy the appa- 
ratus Vand an R. After which V, M, R and D should be set up side by 
side. Let R and D be reduced in length to about 4 feet, and arranged to 
record on a surface similar to M. A broad recording surface requires a 
special clock to drive it, whilst it is expensive and troublesome to handle. 
When this is done, and experiments have extended over two or three 
months, we shall then be in a position to speak more definitely about the 
relative merits of these instruments as earthquake recorders. 
Il. Observations with Pendulums T and U in the Isle of Wight, 1895-96. 
The Localities and their Geology. 
The position of Shide Hill House, where instrument T is installed, is 
approximately 50° 41’ 18’ N. Lat., and 1° 17’ 10’. W. Long. It is near 
to the Shide railway station, at the foot of the western side of Pan Down, 
which is a portion of the chalk backbone of the Isle of Wight. 
Up on the Down the chalk reaches to within a few inches of the surface. 
At Shide Hill House disintegrated chalk, which may have a thickness 
of about 6 feet, is met with at a depth of 3 feet. In front of the house, 
or towards the west, at a distance of about 150 yards at the other side of 
a small stream, there is a railway. Ina N.E. direction, at a distance of 
