1838 REPORT—1896. 
Up to March 27, the boom constructed of varnished straw and reed 
was 2 ft. 5 in. long and weighed #0z. The balance weight weighed 22 oz. 
With a period of 17 seconds a deflection at its outer end of 1 mm. corre- 
sponded to a tilt of 0’71. 
On April 24 this was replaced by an aluminium boom 3 feet in length, 
weighing 4 0z. The balance weight weighs 8 oz. With a period of 31 
seconds, a deflection of 1 mm. at its outer end corresponds to a tilt of 
about 0/2. 
The instrument stands upon the cement-covered top of a brick column, 
which is 1 ft. 6 in. square and 6 feet high. This rises freely ina pit 3 feet 
deep from a thin bed of concrete covering the surface of the disintegrated 
chalk. The sides of the column are oriented N S., and E W. 
The building in which this is placed is an old stable built with brick, 
and sheltered by trees on its north, south, and west sides. From October 
1895 the southern face of the column was covered with cement, which like 
the top was on that day coated with paint. The pit in which the column 
rises is filled with dry straw and hay, whilst for some months the column 
itself was wrapped round with a double thickness of thick felt. 
About the end of June a second instrument which I call U was in- 
stalled at Carisbrooke Castle. It was made by Mr. R. W. Munro, of 
Granville Place, King’s Cross Road, London, W.C. In nearly all respects, 
excepting that of better workmanship, it is similar to the one at Shide. 
It stands on a brick column inside a building, one wall of which is 
the western wall of the Castle, facing the bowling green. With a period 
of 8 seconds its sensibility is such that 1 mm. deflection of the boom 
corresponds to a tilt of about 0’-5. 
The cost of working one of these instruments, which includes benzine, 
bromide paper, used at the rate cf 3 feet per day, and developers, is about 
2s. 6d. per week. To wind and compare the watch, mark the bromide 
papers with a date, and to refill the lamp, which has to be done daily, 
occupies about 10 minutes. Changing and developing the papers once 
-a week can be done in about 45 minutes. The time occupied to analyse 
a diagram depends upon its nature and the exactitude required in the 
necessary measurements. It may be 5 minutesorone hour. The walk to 
Carisbrooke and back takes about 1} hour. 
Artificial Disturbances.—(Blasting, Train and Cart Effects.) 
At a distance of 242 yards on the N.N.W. side of the instrument 
there isa chalk quarry, at which when the present observations commenced 
‘charges of powder of 5 lb. and upwards were fired. Since October 1 the 
‘quantities of powder employed are said to have been reduced, and the 
times of firing the same confined to the half hours between 9 and 9.30 a.m. 
and 2 and 2.30 p.m. 
Although I have several times had the opportunity of watching the 
instrument within 20 seconds of one of these explosions I never observed 
that any appreciable motion had been produced. 
It may therefore be assumed that the instrument was not seriously 
affected by these operations. An assurance of this was obtained by com- 
‘paring the following list of explosions very kindly made by Miss E. A. 
Evelegh, of Shide House, which is within 50 yards of the quarry and a 
