1842.] on the North-Western Frontier. 253 



8. The direction of the Shock. — I am not aware of any instrument 

 having yet been actually employed for ascertaining this point, but the 

 following simple apparatus has been proposed for the purpose by Prof. 

 Babbage, in his admirable little volume on the Economy of Manufactures 

 and Machinery ; and although it must be confessed, that several of the 

 schemes he has proposed in that work, remind us a little of the designs 

 of the sages in Swift's College of Laputa, this is not one of them, but 

 seems adapted to its proposed object. 



" An earthquake," he remarks " is a phenomena of such frequent 

 occurrence, and so interesting both from its fearful devastations, as well 

 as from its connexion with geological theories, that it became import- 

 ant to possess an instrument which shall, if possible, indicate the direc- 

 tion of a shock, as well as its intensity. An observation made a few 

 years since at Odessa, after an Earthquake which happened during the 

 night, suggests a simple instrument by which the direction of the shock 

 may be determined. 



" A glass vase, partly filled with water stood on the table of a room 

 in a house at Odessa ; and from the coldness of the glass, the inner 

 part of the vessel above the water was coated with dew. Several very 

 perceptible shocks of an Earthquake happened between three and four 

 o'clock in the morning ; and when the observer got up, he remarked 

 that the dew was brushed off at two opposite sides of the glass, by a 

 wave which the Earthquake had caused in the water. The line joining 

 the two highest points of this wave, was of course that in which the 

 shock travelled. This circumstance which was accidentally noticed by 

 an Engineer at Odessa,* suggests the plan of keeping, in countries sub- 

 ject to Earthquakes, glass vessels partly filled with treacle or some 

 unctuous fluid, so that when any lateral motion is communicated to 

 them from the earth, the adhesion of the liquid to the glass shall enable 

 the observer, after some interval of time, to determine the direction of 

 the shock. 



" In order to obtain some measure of the vertical oscillation of the 

 earth, a weight might be attached to a spiral spring, or a pendulum 

 might be sustained in a horizontal position, and a sliding index be 

 moved by either of them, so that the extreme deviations might be 



* Memoires de l'Academie des Sciences de Petersburgh, 6me series, tome i. p. 4. 



2 L 



