1842.] on the North-Western Frontier. 251 



the view I have taken of the direction in which the shock was propa- 

 gated. 



The occurrence of Earthquakes throughout these provinces, and 

 indeed throughout India generally, is so frequent, and their connection 

 with geological theories of such an interesting character, that it is 

 highly desirable to facilitate, as much as possible, the collection of mi- 

 nute, well authenticated, and carefully detailed facts relative to these 

 various phenomena. I will therefore conclude this note, by pointing 

 out briefly those points on which information is peculiarly desirable, 

 and the attention of observers is earnestly solicited to them. 



1. The Time. — The startling discrepancies that occur in regard to 

 time, in otherwise most satisfactory accounts of Earthquakes, indicate 

 the great necessity for precaution in observing it, since it is undoubt- 

 edly the point on which the most interesting conclusion relative 

 to such occurrences must be based. When, therefore, the period 

 of a shock is marked by a watch, means ought to be taken, whenever 

 possible, to verify the time shewn by this watch, by some simple 

 celestial observation, or some data should be given by which the time 

 could be ascertained independently within very trifling limits, as 

 for example, by a specification of the exact length of the shadow of 

 a vertical object of fixed and determinate length, on a horizontal level, 

 at a precise moment, not too near noon ; or if near the coast or at sea, 

 the first appearances and last disappearances of the sun's upper and 

 lower border, above and below the sea horizon, etc.* Without this 

 minute identification of time, it is impossible to maintain the connec- 

 tion of shocks felt at far distant places ; calculations of the rate of progress 

 of the undulations or vibrations can only be approximative, and other 

 interesting points are rendered inconclusive. 



2. The Duration. — On this point also, the most striking discre- 

 pancies are to be observed, arising no doubt from each observer making 

 his own sensation the measure of duration, and estimating the latter 

 without reference to some determinate standard. When the mind is 

 intently occupied either by feelings of alarm or intense interest, it is 

 wholly unfitted for estimating duration correctly, and the watch ought 

 only to be trusted. The general tendency is to make the duration 



* Sir J. Herschcil's Meteorological Instruction, Prof. Papers, Roy. Engrs. vol. ii. 



