118 EARTHQUAKES. 



came from the north, or is so stated to have done by the Intendente. Senor Troncoso was 

 absent. This was the last great shock during our stay in Chile. For further details of it, and 

 also of the April earthquakes, the reader may consult Appendix A. 



There were, however, two or three lesser tremors, which merit attention. The first of 

 these was on the night of November 15th, 1851, whilst I was looking with the equatorial 

 telescope at the moon, whose apparent motion from north to south was through quite four 

 minutes of arc. I was unable to detect the least diagonal displacement, other than the tremor 

 inseparable from such disturbance of the base of the instrument. It lasted seven seconds. 

 Owing to a strong wind blowing in at the door of the observatory, the direction of the rumbling 

 noise accompanying it was not distinguishable. Perhaps a similar sight the vision of terres- 

 trial convulsion under a magnifying power of 235 times may never occur again in all my life. 



MAY 31, 1852. 



There was a slight shock about 11A. 30m. A. M., which was felt at Valparaiso, at the same 

 time. 



JULY 5. 



The earth was agitated from Qh. 41m. 03s. to Oh. 41m. 38s. P. M. Its motion was 

 apparently to the southward, in the direction of the longer axis of Santa Lucia, though the 

 meridian circle oscillated tremblingly in the transverse direction through more than a quarter 

 of an inch. The bottle of mercury kept for nadir determinations was shaken so uniformly that 

 it would not serve as a guide to the origin of the disturbing force. The agitation of the surface 

 of the mercury was rather due to a succession of rapid impulses than a series of waves of much 

 amplitude. 



AUGUST 12. 



A line of telegraph (magneto-electric) having been erected between Santiago and Valpa- 

 raiso, the operating director very kindly consented to adopt an earthquake signal. This signal 

 was to be struck at the commencement of a tremor at either end of the line, and the time, 

 noted at the other end, between the receipt of the signal and arrival of the shock, was to be 

 immediately compared by Mr. Mouat's (astronomical) or the observatory clock on Santa Lucia. 

 This was the first we had had an opportunity to observe, and it was more than commonly 

 severe. With an intermission of two seconds, the earth continued in motion from 11 h. 58m. 

 32s. until 11A. 59m. 10s. A. M. ; the second shock having been longest and sharpest. The noise 

 was heard to the N.W. But that which was of most interest was the fact established by the 

 telegraph two cities, 64 miles apart, had been shaken at precisely the same instant when the 

 signal was struck in Valparaiso, the finger of the operator was on the key at Santiago for the 

 same purpose. 



Accurate record of most of the tremors that occurred from November, 1849, to September, 

 1852, are believed to have been kept only at Santiago and Serena; though it is well known that 

 shocks are even more frequent in the province of Atacama than Coquimbo ; and that as one 

 travels southward they are less and less common, untir at Valdivia months pass without one to 

 startle the population. No doubt some at night escaped observers at both specified places ; but 

 when we recollect that the two are only 220 miles apart, it is a matter of surprise that of the 

 218 enumerated in Appendix A, only those of November 13 and 18, 1849, and December 6, 

 1850, were recognised at each of them. Stronger evidence of the limited districts to which the 

 phenomenon is usually confined could not be adduced. Examination of this Appendix develops 

 other facts also. First : That the province of Coquimbo is more liable to disturbance than that of 

 Santiago, in the proportion of 139 to 69, these numbers of tremors having been observed during 



