ON THE EARTHQUAKE AND VOLCANIC PHENOMENA OF JAPAN. 171 
These lists have been compiled without the assistance of instruments, 
and therefore are not so complete as they might have been had the 
records been founded on indications given by seismographs. The latter 
list was made by my friend Mr. J. HK. Pereira,of Yokohama. Altogether 
I find for Yokohama notes relating to 285 shocks, and of these 189 were 
felt in Tokio, or, in other words, 33 per cent. of the Yokohama disturb- 
ances do not reach Tokio. Similarly there may be disturbances peculiar 
to Tokio which do not reach Yokohama. 
VeLocity oF HARTHQUAKE PROPAGATION. 
In the seventh report to this Association (1885), as the result of a 
long series of experiments upon disturbances produced by the explosion 
of dynamite, and by other means, it was stated that velocity of transit 
decreases as a disturbance radiates, that it increases with the intensity of 
the initial disturbances, and that in soft ground the author had recorded 
velocities of from 200 to 630 feet per second, &c. In the same report 
there is a brief account of the simultaneous observation of earthquakes 
at several stations in electrical connection. As one pendulum sent time 
to all these stations, which were 800 or 900 feet apart, on the assumption 
that at a given station, which we will call A, a particular wave, which 
we will call a, could be again reeognised at stations B, C, &c., we had 
here the best possible means of determining velocity. 
As a matter of fact, out of 50 sets of diagrams representing 50 diffe- 
rent earthquakes, it was only in five instances that the same wave could 
be identified at several different stations. The result of these identifica- 
tions led to the calculations of velocities of 5,860, 4,270, 5,984, 2,850, 
and 1,644 feet per second. 
These determinations, however, cannot be accepted without reserve, 
because I find that waves may spread out as they pass from station to 
station, their period may alter, a given wave at one station may split up 
into two waves by the time it reaches the next station, &c. 
Thus on December 16, 1884, I found at station A two waves a and b 
separated by an interval of 1:139 seconds, whilst at station B what 
appear to be the same two waves are 1:277 seconds apart. Hence a 
velocity calculated from the transit of a would be different from the 
velocity of the same earthquake calculated from 6. This sort of obser- 
vation is not uncommon: thus on March 20, 1885, I found at A a wave 
@ 1:99 seconds, and a wave b 4°11 seconds, from the commencement of 
the time ticks. At J these same waves are respectively 3:03 and 5:26 
seconds from the first time tick. From this we must conclude that in 
travelling from A to J the wave a took 1:04 seconds, whilst the wave b 
took 1:15 seconds. ~ 
These observations led to the conclusion that satisfactory results 
could only be expected by timing the arrival of disturbances at points on 
an area of considerable extent, and with this end in view, at the request 
of the Seismological Society, I entered into communication with the 
telegraph department of this country to obtain their assistance in observ- 
ing the velocity of earthquake transit. 
Such assistance they have given for two years, and Mr. W. B. Mason 
of Tokio is now publishing a list of the observations which have been 
made. The stations selected are from 20 to 200 miles apart, and the 
clocks from which the observations are made by personal observation are 
