248 



NATURE 



[January 13, 1898 



to more or less horizontal displacements applied at the 

 foundation, have been largely adopted in the building of 

 houses and the works of engineers, is a testimony 

 that they have been well worthy of consideration. The 

 correctness of the new methods is found in the fact that 

 in very many instances tall chimneys, as well as those of 

 ordinary buildings, together with buildings themselves 

 embodying the new principles, remain standing, whilst 

 the old types have fallen or at least been shattered. 

 When we remember that on June 15, 1896, Japan 

 lost nearly 30,000 of her people by earthquakes and sea- 

 waves, that on October 28, 1891, the loss of life was 

 about 10,000, and the cost to restore railways and other 

 works involved an outlay of approximately 3,000,000/., that 

 the Calcutta earthquake on June 12, 1897, is to be fol- 

 lowed by an expenditure of 35 lahks of rupees for the 

 restoration of public works, for the payment of which the 

 Chief Commissioner of Assam applies for a grant from 

 the Imperial revenue, the importance of anything which 

 will minimise the effects of these great catastrophes can 

 not be over-estimated. 



In Japan engineers and builders are already crystal- 

 lising the results of experience and experiment, and 

 stereotyped methods of construction are being gradually 



ance died out, or as it radiated. A wave which had a 

 slight notch upon its crest by the gradual growth of the 

 riplet, as the motion radiated from its origin, was seen to- 

 change into a double wave. Within 50 or 100 feet of ani 

 origin, the first movement was due to a wave of com- 

 pression, but beyond this distance a separation between 

 normal and transverse movements was not observable. 



The manner in which a shadow area, formed behind a 

 cutting or hill, was invaded by movements creeping round 

 the two ends of the obstrifction was remarkable. These 

 and many other results were confirmed and extended by 

 actual seismograms obtained from a series of stations 

 situated on a piece of ground less than ten acres in area. 

 The motion on one side of this piece of ground was in- 

 variably so much greater than it was upon the other side, 

 that it afforded an explanation of the peculiar distribution 

 of ruin, sometimes observed in a city after a disastrous 

 earthquake. 



The fact that the side of greater motion was that, 

 where the ground was soft, and the confirniation of this 

 by observations in other localities, was a matter that at- 

 tracted the serious attention of architects and builders. 

 Another observation which has received many practical 

 applications, especially in connection with the foundation 

 of buildings, was that at a depth of 10 or 20 feet the 



Fig. 4. — Gravestone as seismometers, indicating direction-and intensity of 

 movement. (Omori.) 



abandoned, with the result that after fire, flood, or earth- 

 quake, or as other opportunities present themselves, new 

 types of structure are growing up, which have already 

 shown themselves to be better than the old. 



Even if these results represented everything that the 

 pioneers of the new seismology had achieved, they carry 

 with them a feeling of satisfaction that the study of 

 earthquakes has not been altogether unfruitful, but has 

 led to that which is practical and simple in its ap- 

 plication. 



The experiments in which vibratory movements of the 

 ground were produced by artificial means, whilst repro- 

 ducing and affording an explanation of many phenomena 

 observed or expected in earthquake disturbances, directed 

 attention to others, the existence of which was for the 

 first time rendered probable. 



The velocity of propagation of wave motion evidently 

 increased with the intensity of the initial disturbance ; it 

 was greater for vertical and normal than for transverse 

 waves, whilst motion was propagated more rapidly to 

 stations near an origin than between stations which were 

 at some distance from the same. 



The period of the movements increased as a disturb- 



NO. 1472, VOL. 57] 



Fig. 



— Destruction of an ordinary European structure (a cotton mill at 

 Nagoya) by the earthquake of October 28, 1891. (Burton.) 



movements of the ground were found to be less than 

 they were upon the surface. 



The seismic survey of North Japan, which has been 

 extended to cover the whole empire, shows clearly that 

 the volcanoes, extending for the most part along the back- 

 bone of the country, have no immediate connection with 

 the earthquakes, nearly all of which originate along the 

 eastern seaboard. Many of the largest of these have 

 their home beneath water which in certain places exceeds 

 a depth of 4000 fathoms, and it is in these sub-oceanic 

 recesses at the base of a continental dome where a cer- 

 tain class of geological activities, which from time to 

 time are announced to us by the shaking of the ground, 

 are most pronounced. 



The earthquakes of one region have been separated 

 from those of another, whilst the land area which was 

 sensibly shaken by each disturbance is well known. 



The advantage of these registers when, for example, we 

 seek for a connection between earthquakes and lunar 

 attraction, or the rising of the tide upon a coast, because 

 these influences attain a maximum in different localities 

 at different hours, must be apparent. 



Thanks to Dr. C. G. Knott, who first subjected earth- 

 quake statistics to rigid analysis, to Dr. C. Davison, 

 who so ably emphasised and extended these methods of 



