872 
MESSRS. J. MILNE AND T. GRAY ON SEISMIC EXPERIMENTS. 
In fig. 2 these central motions were performed in a direction inclined at about 45° 
to the first motions. 
In fig. 3, about which it may be remarked that other diagrams taken at the same 
station were very similar, a lemniscate-like motion is exceedingly well pronounced. 
The shaded portions of these three figures indicate the parts where the lines were so 
numerous that they could not be distinctly separated from each other. 
The stations at which these figures were drawn and the fall of the ball to which 
they correspond are indicated beneath each. 
In the first column of the following table a number is given showing on which fall 
of the ball the experiment was made. The second column indicates at which station, 
or the distance in feet from the point where the ball fell, at which the experiment was 
made—with the exception of the fall No. 23 all these stations are on the line A D. 
The third column shows the maximum amplitude of the normal, and the fourth 
column that of the transverse motion—excepting the falls 27, 28, and 29 (see 
Remarks), the weight fell 35 feet. 
Maximum amplitudes. 
Number 
Station. 
Remarks. 
of 
fall. 
Normal 
Transverse 
vibrations. 
vibrations. 
feet. 
millims. 
millims. 
9 
50 
7 
4-5 
The hall fell on a block of iron. 
10 
50 
10 
2-5 
Transverse motion not very distinct. 
11 
50 
10 
2-25 
J) >> 
12 
100 
4-5 
2 
Transverse motion at an angle of about 45° with the normal 
vibrations. As the ground hardened under the weight, the 
transverse vibration apparently became less. 
13 
14 
100 
100 
3-5 
3-5 
2-75 
3 
f The character of the records drawn for these two experiments 
j 
are very similar, but slightly different from that obtained 
L from Fall No. 12. 
15 
16 
200 
200 
Q 
1*5 
1*5 
f These two records appear to be exactly the same, the trans¬ 
di 
2 
i 
verse motion is now more than at right angles to the normal 
motion. 
17 
100 
4*5 
2 
18 
100 
4-25 
2*5 
20 
150 
5 
3*5 
21 
250 
2 
1-5 
Not completely written. 
22 
250 
1’75 
1*75 
Somewhat complicated. 
23 
130 
1 
1*25 
This record was made at the 130 feet station on A E. 
26 
50 
9 (?) 
5 
The record is somewhat confused. 
27 
50 
8-5 
4*5 
Ball only fell 25 feet. The record is not good. 
29 
50 
9 
2 
Ball only fell 11 feet 1 Transverse measurements represent the 
30 
50 
8 
2-5 
„ „ 8 feet j breadth of the normal ellipses. 
