MESSRS. J. MILNE AND T. GRAY ON SEISMIC EXPERIMENTS. 883 
gives a good indication of the nature of the actual movement in the earth. It would 
appear also from these, and from subsequent records, that the direct vibrations, 
although the largest at first, die out more rapidly than the transverse motions. This 
may have an interesting bearing on the direction observations in earthquakes. 
The apparently quicker rate of vibrations of the normal motions, as compared with 
the transversal movements, is a point worthy of attention. Also the quicker rate of 
either of these sets of vibrations as compared with the average rate of vibration as 
experienced in any of the recent earthquakes in Tokio may be noticed. It may also 
be remarked that the actual earthquake records show a motion which is usually 
exceedingly irregular. 
The actual displacement of a particle from its normal position in the artificial 
disturbances seems never to have been above 0*5 millim. at a distance of 50 feet, 
and at a distance of 250 feet it seems to have been from 0*1 to 0*05 millim. Perhaps 
the most remarkable point made out from these experiments is the very slow rate at 
which the disturbance is propagated. The experimental verification of the slower rate 
of propagation in transverse vibrations is also interesting. 
This slow rate of propagation accounts for the observation, so often made when 
earthquakes take place in Tokio, that a rumbling sound precedes them. This rumbling 
sound is no doubt in many cases the cracking and creaking of buildings reaching the 
ear through the air sooner than the disturbance in the ground becomes sensible. It 
is possible that very reliable observations of direction and locality from which the 
disturbance emanates may be founded on this. 
In conclusion, we beg to tender our best thanks to the directors of the Akabane 
Works for the facilities given for the carrying out of our experiments ; to the Telegraph 
Department for the loan of wire; to Messrs. Tamaki, Kitaka, and other gentlemen 
who from time to time afforded us assistance in taking observations. 
