372 
REPORT— 1854. 
elements of great shocks, by one instrument. It would seem, therefore,wi^ 
to keep the observations separate; namely, that for time, by itself; for vertical 
direction, and intensity of force in that direction, by itself; and for progressive 
direction and intensity, by itself. 
Supposing only the time observed, how interesting would be the fact, that 
in a long line subject to such frequent disturbances, some were common to 
two, some to three places, and so on; and, in like manner, that the place 
of greatest disturbance should be found to shift, being, for example, in the 
Ionian Islands, at one epoch at Zante, at another at St. Maura, and so on! At 
present only great shocks are noticed, but in such regions many minute shocks 
might intervene between them. The vertical and the horizontal intensities, 
or the extent of the vibrations in those directions, should also be recorW 
or observed separately ; but the real difficulty in any ordinary instrument ’» 
to make it record more than one shock without re-adjustment; still, howe'er, 
bv making the periods of examination ami adjustment at very short interval*, 
there can be little doubt that all great shocks would be very closely register* 
The chances of overcoming the difficulties will be greatly increased by keepin; 
each function separate; namely, the shock in its vertical component, tin 
shock in its horizontal component, and the time of shock; and by due attend * 
to any one of these functions, very much improved systems of registry ^5 
be devised. And it is probable even that a fitter method may be discovcm 
for determining the intensity by some other means than the angular motion, 
even by using solid instruments. I hope, indeed, to obtain some data 1 f 
this purpose by means of the vibrations in heavy guns, &c. at\AookjV ‘ 
not, however, desiring to interrupt in any way the progress of Mr. Malleti 
researches; though it is evident that simple and yet accurate forins ot 
instruments, cheap in construction so as to be multiplied for as many ph Cl1 
as possible, and easy of manipulation so as to be trusted to ordinary observers, 
are the present desiderata. 
The disc instruments constructed by Major James, though conforming 10 
the general principle suggested by me, as the organ of the Committee,^ 
probably deficient in weight, and would, therefore, oppose too little mnj-' 
to a severe shock to preserve them from irregular oscillations; but® 
defect can be easily remedied, they deserve a practical trial. Maj nr 
has also had constructed a simple pendulum for the same purpose, f ■ 
another provided with a weight suspended by a spiral spring surround ; - 
the rod of the pendulum, and attached to its upper end, the object of 
is to register the vertical aud horizontal movements at the same timf*'-' 
mode of determination which had also been suggested by Mr. 
These instruments deserve also to be fairly tried, as they will anquesl«oj»M 
give valuable information on some, though not on aU, the elements of I • 
important subject ; but it is hoped that, hereafter, those who pursue 
subject will endeavour to perfect the observations of each element oi 
however > forgetting, that it is also desirable so to ho 
together, that every shock may be referred to its true epoch. 
