Proceedings of the British Association, 



575 



to Mr. Macfarlane's house, indicated an upheave of the ground to the 

 extent of a quarter of an inch. From a review of all the details, it 

 seems probable that the particular spot from which the earthquakes 

 emanate, is situated about one mile N.E. of Duniva House, and one and 

 a half or two miles N. W. of Comrie ; and it is considered desirable to 

 place additional instruments at Duniva, and in the neighbourhood, 

 with the view of approximating still nearer to the exact spot of emana- 

 tion. 



The additional instruments for indicating earthquake shocks, lately- 

 sent out, are seven in number. 1 . Four of these are on the principle of 

 the watchmaker's noddy, explained in last year's Report. — 2. Another 

 instrument consists of four horizontal glass tubes slightly turned up at 

 each end, and filled with mercury. These tubes are laid down on 

 the solid floor of a room, according to the points of the compass ; 

 and it is expected that when a shock takes place the mercury will flow 

 out of one or more of these tubes. If there is no horizontal movement, 

 but an inclination of the ground only, the mercury will flow out of the 

 tube or tubes affected by the inclination. This instrument was made by 

 Mr. Newman, of London, under the directions of Professor Wheatstone 

 and Mr. D. Milne. — 3. The two remaining instruments are intended 

 exclusively to indicate vertical movements of the ground. They consist 

 of a horizontal bar, fixed to a solid wall, by means of a strong flat 

 watchspring, and are loaded at the opposite end. If the wall suddenly 

 rises or sinks, the loaded end of this horizontal rod remains from its vis 

 inerticB nearly at rest, and thus can move any light substance (as 

 paper or a straw) brought against it by the vertical movement of 

 the ground ; the light substance being so adjusted as to remain fixed 

 wherever the rod moves it. 



Beside the above instruments, a barometer, a double thermometer, 

 and a rain-gauge, have been sent to Mr. Macfarlane, of Comrie, in order 

 that the state of the atmosphere at the time of the shocks, and the 

 nature of the weather generally, during their occurrence, may be ascer- 

 tained. The Committee, however, think it desirable to procure instru- 

 ments much more sensitive than any which they yet possess ; and they 

 particularly call attention to the importance of carrying on meteorolo- 

 gical observations at Comrie, as there seems to exist strong grounds for 

 the opinion entertained by many, of an intimate connexion between 

 earthquake shocks and the state of the weather, or rather the various 

 agents which affect the weather. The Committee have not yet attempt- 

 ed the registration of earthquake shocks in any part of the country 

 expect Perthshire; but as the primitive districts of Cornwall and 



