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IV.—On the Objects, Construction, and Use of certain new Instruments for 
Self-registration of the Passage of Earthquake Shocks. By Roxserr 
Matter, Esq., Mem. Ins. C. E., M.R.I.A., Pres. Geol. Soc. Ireland, &c. 
Read June 22,1846. 
INSTRUMENTS previously designed for this purpose have not possessed the 
power of self-registration; they have consisted either in the trace left by the 
motion of a viscid fluid on the containing vessel, when the latter is shaken, or 
they have been upon the principle of the inverted pendulum, or watchmaker’s 
noddy. Instruments so constructed are objectionable, because, having themselves 
times of vibration of their own, which may conflict with those of the earthquake 
shock, they are liable to fail_for want of delicacy. They also possess several 
inconveniences of a mechanical kind, in being adapted to self-registration. 
The objects to be attained in the instruments which the author has had in 
view are: 
The self-registration— 
Ist. Of the time of transit, or “ wave period,” at a given point of the earth’s 
surface, of an earthquake shock, or earth wave, noting same to a small decimal of 
a second of time. 
2nd. Of the vertical element of dimension, or altitude of the earth wave, at 
the moment of its transit, whether the wave be a positive or a negative one. 
3rd. Of the horizontal element of dimension, or amplitude of the wave, at 
the same moment. 
4th. Of the direction, as to azimuth, of the wave transit. 
The principle adopted, by means of which the wave or shock shall act in 
giving motion to the instrument, consists in availing ourselves of the oscillation 
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