220 EEPOET— 1893. 



Burton, are particularly sensitive, I am inclined to the opinion that there 

 was less tilting accompanying these earthquakes than there is in the 

 waves which constitute a tremor-storm ; in fact, the earthquakes which 

 only produced deflections of 2 mm. were elastic tremors, while so-called 

 tremors which may produce deflections of 25 mm. are earth- waves. 



These observations led me to note the effects produced upon a film 

 when the mirrors had been caused to swing by placing my finger upon 

 the iron bed-plate which acts as their support. The result was that 

 either a band about 12 mm. in length was produced or else the trace 

 was blurred, and at the blurr a permanent deflection of about 3 mm. was 

 recorded. 



As a result of these experiments I conclude that in all cases where 

 lines are invariably opposite to each other in both components, and 

 are seen as transverse markings in the traces, such lines indicate that 

 the mirrors have been swinging, and the question arises, whether these 

 are due to undulations from distant earthquakes or whether they are 

 due to undulations which, if they were continuous, would constitute a 

 tremor- storm. 



If they are tiltings due to distant earthquakes, then on several occa- 

 sions as many as fourteen of these disturbances have been noted in 

 twenty-four hours. On other days the normal lines are unbroken. 



Comparing the photographic traces with the list of 101 earthquakes 

 which were felt in Japan during the month of February, it is seen that 

 only the large ones, like numbers 54 and 61, have been recorded on the 

 film. The traces, however, show that there have been many large dis- 

 turbances which do not coincide iu time with earthquakes noted on the 

 list. It is possible that these may coincide with disturbances which had 

 their origin in other countries, or, what is more likely, with disturbances 

 originating beneath the bed of the Pacific, where, from what we know, 

 seismic activity is at least as great as it is upon the land. An alternative 

 suggestion is that they are the result of movements similar in character 

 to those which constitute a tremor-storm ; but whether these are to be 

 attributed to sudden but gentle bondings of rocky strata, or whether 

 their origin is to be sought for amongst causes which are more complex, 

 is for the present a subject about which we are hardly justified in 

 attempting to formulate an hypothesis. 



Dr. von Rebeur-Paschwitz in Germany has observed fourteen earth- 

 quakes — if all of these really are earthquakes — in eleven months. One 

 of them corresponds in time to the great disturbance of October 28, 1891, 

 when Central Japan was devastated. 



Possible Connecticut lehveen these Observations and oilier Phenomena. 



Assuming that with appliances similar to those used by Dr. von Rebeur- 

 Paschwitz, or to those used in Japan, records of distant earthquakes may 

 be noted, then it would be possible in England, or any other country, not 

 only to note unfelt local disturbances, but also to record, at least, very 

 many of the large disturbances which occur throughout the world. 



The importance of such records in determining the velocity with 

 which earth-waves are propagated, or, as was suggested by Lord Kelvin, 

 the determination of elastic constants for the earth's crust, and in solving 

 other problems, is apparent. 



Already the observations on earth-tilting seem to have gone sufficiently 



