ON SEISMOLOGICAL INVESTIGATION. 185 
242 yards, there is a chalk quarry, where at certain fixed times blasting 
takes place. 
At the back of the house within a few yards of the buildings in 
which the instrument is placed there is a lane down which on week days 
carts heavily laden with gravel pass. 
Through the kindness of Mr. A. Harbottle Escourt, Deputy Governor 
of the island, I was enabled to establish a second instrument (U) within 
the grounds of Carisbrooke Castle. The foundation is similar to that at 
Shide, being a brick column built up from the chalk. This stands in a 
small room, one wall of which is the western wall of the castle. Towards 
the east it faces the Bowling Green. 
This instrument gave its first records about June 22, but it was not 
in proper working order until the middle of July. 
Shide lies at a distance of 1} mile in a N.N.E. direction from Caris- 
brooke. Mount Joy, which is 274 feet high, lies between the two places. 
At Shide and continuing towards Carisbrooke the chalk ridge, which 
forms the backbone of the island, strikes E.S.E. to W.N.W., and dips at 
at a high angle approaching verticality towards the north. The central 
portion of this anticline has been removed by denudation, whilst its 
southern, which dips gently, can be seen in the Downs along the south 
coast. 
The steep dip on the northern side of this anticline is a feature 
cominon to the folds of the continuation of these rocks. Sudden mono- 
clinal folds are generally recognised as representing movements, which 
if continued result in faulting, and the home of faults is that of 
earthquakes. 
The faults which are actually visible or inferred from the displace- 
ment of beds in the Isle of Wight are only seven or eight in number, 
and the throw of those, excepting the one supposed to exist a few miles 
east of Shide at Ashey, is but small (see ‘The Geology of the Isle of 
Wight,’ by H. W. Bristow, revised and enlarged by Clement Reid, and 
Aubrey Strahan, ‘ Memoirs of the Geological Survey,’ 1889). 
The structural and the stratigraphical conditions which I have per- 
sonally observed at Shide and its neighbourhood are as follows. The 
chalk is so sharply tilted that it is reasonable to suppose that limits of 
its elasticity have often been exceeded. As a result of the pressure and 
metamorphic actions accompanying this distortion, the chalk has been so 
far hardened that when two pieces of it are struck together it has almost 
the ring of crystalline limestone, the flints if not broken into fragments 
have been brought together in patches, and have been so far fractured 
that by the application of light blows they fall in pieces. Siliceous 
matter has been deposited in veins, whilst slickensided surfaces in 
various directions apparently indicate that from time to time strain has 
been relieved by minor yieldings. 
At Alverton chalk pit, which lies to the west of Carisbrooke, the 
chaik dips northwards at about 45°. Parallel to the dip the strike, and 
in intermediate directions the beds, are traversed by fractures which can 
‘be traced over lengths of 20 yards. 
That these fractures are not mere cracks but are accompanied by 
displacement, and therefore have the character of true faults, is shown in 
one instance by the abrupt termination of a band of flint where it meets 
one of these lines, in another case, as also at Shide, it is shown by the 
smashing up of a mass of flint and the trailing out of the fragments of 
