64 REPORTS ON tBe STATE OF SCIENCE. 



aud the Himalayan ridges. The totals for these groups of districts show 

 that the greatest seismic activity has been on the Asiatic side of the Paciflo 

 Ocean, particularly in the East Indian Archipelago. The least disturbed 

 district has been the west side of South America. Another feature of 

 interest shown by these totals is that from the year 1902 they rise and fall 

 together ; that is to say, seismic frequency on the two sides of the Pacific 

 has fluctuated similarly. From this we may infer that seismic frequency 

 in a district is not entirely governed by local influences, but largely by 

 influences which extend over very large areas. As illustrative of the.«e 

 latter influences attention may be called to the redistribution of surface 

 materials by ocean currents, or to stresses which may accompany unusual 

 changes in the path followed by the pole of our earth. 



V. A/ter'-shocks of the Jamaica Earthquake, January 14, 1907. 



In an official report. No. .33a, on the earthquake of January 14, 1907, 

 by Maxwell Hall, the time given for the commencement of the main dis- 

 turbance is 3.29 P.M. (Jamaica time). The difference in longitude between 

 Kingston and England is equivalent to 5h. 7m., and the time which 

 laro-e waves would take to travel between these places or 67° would be 

 43m. The time at which this particular phase of motion would be 

 recorded in England would approximately be 21h. 19m. (Gr.M.T.) 

 Inasmuch as Mr. Maxwell Hall's time refers to an observation made at 

 Chapleton, and not at Kingston, we should expect the arrival of waves 

 in England to be one or two minutes earlier than the time we have just 

 given, and as a matter of fact they were recorded at the Isle of Wight at 

 21h. 17m. During the night of the 14th and 15th, we learn from the 

 same report that 15 shocks were counted at Kingston. The times at which 

 these occurred are not given, but as they appear to have been noted by 

 persons out of doors we regard them as the more violent members of 

 a much larger series. In the Isle of "Wight small disturbances were 

 recorded on the 14th at 23.40, 23.45, 23.52, and on the 15th at 0.2, 0.22, 

 0,32, 0.41, 0.43, and 0.45. We cannot say with certainty that these had 

 their origin in the West Indies ; it is, however, extremely likely that 

 this is the case. With regard to many of the shocks in Jamaica, the 

 times of which are given by Mr. Maxwell Hall, the case is different. 

 Between January 14, 7.5 p.m., and July 5, 2.10 p.m. (Jamaica time), 14S 

 disturbances were recorded. Corresponding to 51 of these a seismograph 

 in the Isle of Wight shows groups of tiny tremors, each of which was 

 recorded at practically 43 minutes after a shock in Jamaica. The con- 

 clusion therefore is that the tremor groups i-epresent after-shocks which 

 have been sufficiently intense to traverse a distance greater than the 

 width of the Atlantic. They do not appear to have been recorded at 

 Strassburg, Gottingen, or I^aibach, although the distance of these places 

 is but little greater than the distance to the Isle of Wight. As this is 

 the first time that a series of after-shocks has been recorded so far from 

 their origin, and as the records of the same illustrate the high sensibility 

 of the Milne horizontal pendulum, I give a list of these movements. 



