864 
MESSRS. J. MILNE AND T. GRAY ON SEISMIC EXPERIMENTS. 
The following are the principal points towards which we have directed our attention 
with regard to the resulting vibrations. 
1. The difference in the magnitude and character of the motions produced at stations 
variously situated with regard to the point at which the blow was struck. 
These stations were sometimes taken on a level plain at different distances 
from the origin of the motion. At other times they were taken at various 
points on the side and summit of a hill. They were also taken so that a deep 
cutting in the form of a pond intervened between the point where the blow was 
struck and the observing station. 
2. The relation between normal and transverse vibration as simultaneously exhibited 
at various stations. 
3. The velocity of transmission of normal and of transverse vibrations. 
The Akabane Engineering Works where these experiments were carried on are 
situated on the southern side of Tokio, upon a flat alluvial plain bordering a low spur 
running out from one of the table-land-like elevations which characterise certain 
portions of the city lying at a short distance from the sea board. The soil, with the 
exception, of that wliich is immediately upon the surface, may be described as a 
hardened mud, very similar in character to that which is now being deposited in the 
delta-like formations at the mouths of the various rivers which enter the bay. 
The plan which is attached (Plate 52) shows the general arrangement of the works. 
The buildings which are shaded are built of brick ; the others are light structures built 
of wood. The ball which gave the shock was always dropped at the point A, it weighed 
1,710 lbs., and could be conveniently raised up to a height of 35 feet. 
The stations where the effects of the blows were observed are on the lines A B, A C, 
A D, &c. 
The stations on these lines are distinguished from each other by numbers indicating 
their distance in feet from the point A where the ball fell. The only exception to these 
are the stations on the line J K, which are marked according to their distances in feet 
from the comer of the pond J. 
The sections on the lines A E and A H will give the contours of the hill. The pond 
has perpendicular walled sides, and is about 10 feet deep. The lines A B, A C, A D 
are along ground which is practically level. At the commencement of the experiments 
the ground was somewhat soft, and the ball at the first few blows sank to a considerable 
depth. 
We may here call attention to the fact that the vibrations which we have investi¬ 
gated, as in the case of vibrations produced in Mr. Mallet’s experiments by an 
explosion of gunpowder, are the result of a disturbance produced on the surface of the 
ground, whereas in actual earthquake motion it is quite possible that the disturbances 
we feel may have an origin which is deeply seated beneath the superficial crust. The 
only advantage which we can claim for our method of producing vibrations, as com- 
