88 REPORT—1850. 
Letter to the Assistant General Secretary to the British Association. 
Dublin, July 22, 1850. 
My pear S1r,—As the working member of the Committee appointed at last 
meeting of the Association for the instrumental admeasurement of earthquake 
waves, I have to report as follows: —A sum of £50 was placed at the disposal 
of this Committee, the entire amount of which has been devoted to the com- 
pletion of a self-registering seismometer, upon my construction. In this con- 
siderable progress has been made, and we hope to present it in action at the 
next meeting of the Association after the present one, it being found imprac- 
ticable to have it completed in time for the Edinburgh meeting. 
When so finished and found, as we trust, to answer its purpose, it would 
be most desirable that a second instrument at least should be constructed, and 
that both should be sent out and kept at work in whatever earthquake di- 
strict might appear most favourably circumstanced for registration. 
The island of Zante and some other one or more moderately distant stations 
in the Levant, would seem to offer great inducements to fix on them. I have 
reason to know that competent persons could be found at Zante to undertake 
the task of superintending the instruments and recording their indications. 
After such a conjoint arrangement for self-registering observations of the 
peculiarly manageable and almost constant shocks felt at Zante and its sur- 
rounding regions, should have been in operation for a year or so, we might 
expect to arrive at some very definite knowledge as to the position and the 
depth below the surface of the centre of those frequent impulses, in other 
words, probably, of the actual depth of the great volcanic focus of the Me- 
diterranean basin. 
The whole sum of £50 has been drawn, and the whole, with the exception 
of a small sum, remains as yet to the credit of the Committee, but will very 
soon be required for payment. 
Should a second instrument hereafter be constructed a further grant will 
be necessary. 
Previous to the appointment of this Committee at the last meeting, I had 
arranged and in part proceeded with a series of experiments for the experi- 
mental admeasurement of the rate of transit of waves of impulse (analogous 
to those of earthquakes) produced artificially in various coherent and inco- 
herent formations of the earth’s crust, and at first proposed that the expense 
of these experiments should be defrayed from the grant made to this Com- 
mittee at Birmingham ; but finding that the cost of the seismometer for self- 
registration would, as a first instrument, involving alterations, &c., absorb 
nearly the whole grant, if not the whole, and that the expense of these transit 
experiments would be very considerable, I. proposed to the other members of 
the Committee that the whole grant should be devoted to the seismometer, 
and that I would complete the experiments on rate of wave transit, as I had 
commenced, from my own resources. 
I have already completed that class of those experiments that regard the 
rate of impulse-wave transit in ¢coherent formations, and with very interest- 
ing and unexpected results, and am now proceeding with those in coherent 
or rocky formations. The impulses in the former case were produced by the 
explosion of rather large quantities of gunpowder. In the latter it will pro- 
bably be found most convenient to resort to a blow delivered by the fall of 
a heavy body. 
I propose giving an account of these experiments as a portion of a second 
report on the facts of earthquakes, should I be directed by the British Asso- 
ciation, at its approaching meeting, to prepare such report. In this would also 
be embodied the extended catalogue of earthquakes, and discussion of same 
