362 REPORT—1885. 
Fifth Report of the Committee, consisting of Mr. R. ETHERIDGE, 
Mr. THomas Gray, and Professor JoHN MILNE (Secretary), 
appointed for the purpose of investigating the Earthquake 
Phenomena of Japan. (Drawn up by the Secretary.) 
On account of an excursion which I have the intention of making during 
the coming summer to Australia and New Zealand I am compelled to 
draw up this report a month earlier than usual. As the only time when 
the work of attending to observations and experiments repays itself is 
during the winter months, I may safely say that my intention of shorten- 
ing the time usually devoted to earthquake observations is not likely to 
involve any serious loss. 
If we refer to the records of the last year—that is to say, from the end 
of April 1884. to the end of April 1885—it will be seen that the opportunities 
for making observations have been unusually good. The number of 
earthquakes felt during corresponding periods in two previous years and 
this last year was respectively twenty-six, thirty-nine, and eighty. 
Not only have the earthquakes been numerous, but some of them 
have been pretty stiff, as is testified by the fact that on several occasions 
chimneys fell and walls were cracked. 
The work done during the last year is briefly as follows. 
Seismic Experiments. 
From time to time I have had the honour of reporting to the British 
Association on seismic experiments. These experiments were commenced 
in conjunction with Mr. T. Gray in 1880. The movements which were 
then recorded were produced by allowing a heavy ball, 1,710 Ibs. in 
weight, to fall from various heights up to thirty-five feet. Subsequently 
many experiments were made by exploding charges of dynamite and 
gunpowder placed in bore-holes. The observations which were made 
upon the resultant vibrations of the ground were very numerous. As 
examples of them may be mentioned—the determination of the nature of 
earth vibrations as deduced from diagrams, the velocity of propagation of 
different kinds of vibrations, the relative motion of neighbouring points 
of ground, experiments on the production of earth currents, experiments 
on projection and overturning, &c. 
During the last year, whilst working up the long series of records 
which accumulated, several laboratory experiments were made to inves- 
tigate the methods to be employed when analysing the diagrams of earth 
motion. 
The first of these experiments consisted in projecting a small ball 
from the top of a tall flat vertically-placed spring, and at the same time 
causing the spring to draw a diagram of its motion. From the distance 
the ball was thrown its initial velocity could be calculated. From the 
diagram, either by calculation on the assumption of simple harmonic 
motion or by direct measurement, the maximum velocity of movement 
could be obtained. 
These three quantities practically agreed. The most important result 
obtained by these experiments was that they indicated an important 
element to be calculated in earthquake or dynamite diagrams, and, further 
