November 9, 191 1] 



NATURE 



47 



purely sporting articles, we may confidently state 

 that, in spite of a certain number of errors and short- 

 comings, like those mentioned above, the " Encyclo- 

 pasdia of Sport " supplies in the main exactly the kind 

 of information on natural history subjects the sports- 

 man is likely to require, R. L. 



THE PROPAGATION OF EARTHQUAKE 



WAVES.' 



" r^OS PALABRAS," or "two little words," has a 



■L>' much more friendly sound than the abrupt 

 word "preface." "Preface," standing by itself, is sug- 

 gestive of a snappy military command, something 

 like "halt" or "quick march," whilst "Dos Pala- 

 bras " is the kindly invitation of a writer to the public, 

 .asking them to read his work. In the " Dos 

 Palabras " we are told that the ordinary person only 

 thinks about earthquake prediction and that which is 

 utilitarian, whilst the principal object of the seismolo- 

 g'lst is to extend human knowledge about the interior 

 of our planet. 



This memoir, which was presented to the American 

 International Congress of Science held in Buenos 

 Ayres in 1910, although dealing especially with 

 the propagation of earthquake waves, gives in 

 ^n introduction of forty-two pages a rapid review of 

 many problems with which modern seismology deals. 

 From the velocity with which earthquake waves are 

 propagated through our world, we have already 

 learned something new about the constitution of its 

 interior. The conclusions arrived at by these veloci- 

 ties as bearing upon the rigidity of our world, to- 

 gether with investigations made by LxDrd ' Kelvin and 

 others on the same subject, are briefly mentioned. 

 References are made to the investigations of Prof. 

 Ricco which indicate a relationship between the value 

 of gravity and the seismic and volcanic phenomena 

 of a district. But the more general relationship be- 

 tween the abnormal movements of magnetic needles, 

 -arthquake disturbances, and the value of g in locali- 

 ties characterised by the presence of volcanic rocks, 

 has been overlooked. 



Sunspots, unusual movements in bodies of water, 

 the times at which geysers erupt, barisal guns, 

 microphonic disturbances, abnormal earth currents 

 and other phenomena, are pointed to as subjects which 

 should arrest the attention. 



Unexpected side issues in the daily work of a 

 seismologist — as, for example, the effect of tidal load, 

 the transpiration of vegetation, which is always 

 Avrinkling the face of our globe, the emotional effects 

 produced by earthquakes upon man, their effects on 

 the behaviour of certain animals, and the exploitation 

 of many other byways — have been overlooked. These, 

 however, have nothing to do with Dr. Negri's chief 

 subject, which occupies the next seventy-three pages of 

 his publication. This entirely deals with the velocity 

 with which earthquake motion is propagated. He 

 starts out with the assumption that in a teleseismic 

 record we frequently see many phases, P,, P^, &'C., 

 and that there are as many corresponding velocities 

 which are distinguished as V,, Vj, &c. He de- 

 rived this idea from the publications of Dr. Omori. 

 With this assumption V, has a velocity of about I2'5 

 kilometres per second, Vg would be about 2 kilo- 

 metres per second, and V^^, if there is such a value, 

 would be less than 0*5 per second, i.e. if all these 

 'phases of earthquake motion started from an origin 

 at the same time. We fear that many seismologists 

 will not readily accept this hypothesis, and to explain 



1 " Velocidad de Propapicirtn de las Ondas Sismicas." Ry Dr. G. Negri. 

 "Traduccion de Alfredo Torcelli. Pp. 143. (La Plata : Observatoria Astro- 

 oiomico, 191 1.) 



NO. 2193, VOL, 88] 



the rising and falling in amplitude and changes in 

 period exhibited in teleseismic writings will require 

 some other assumption. P^, P^, P3, and their corre- 

 sponding velocities, are explicable by the existence of 

 three types of waves, but the lengthening of the 

 caudal appendage of a megaseism as it travels into 

 and sometimes beyond its quadrantal region is a 

 phenomenon about which many explanations have 

 been offered, but the one to be accepted does not 

 appear so far to have been decided on. 



In his conclusion to this section, Dr. Negri says 



that ihe relation of ,\ —3- (sic), Z\ &c., represents a 



series m mcreasmg arithmetical progression. All 

 that the majority of seismologists at present recognise 

 is that in round numbers V^ equals 12 kilometres, \\ 

 equals about 6 kilometres, and V3 about 3 kilometres 

 per second, and we fear that they are not yet in a 

 position to accept values which might correspond to 

 ^20 or P^^. In an appendix the author shows that 

 his acquaintance with modern seismology is rather 

 one-sided. He gives a bibliography of 176 books and 

 papers, nearly all of which are in the Italian or 

 Spanish language. Japan is credited with thirteen 

 papers, England with five, whilst two or three 

 are in French. The first exhibition of seismological 

 instruments, we are told, was represented by a 

 section in the International Exhibition of 1900 in 

 Paris. The exceedingly popular exhibition of earth- 

 quake instruments held in Tokio twenty years earlier 

 is not even mentioned. The author concludes his 

 memoir by two queries : Why do not all the students 

 of seismology in South America combine? Why 

 does not the national authority do something to bring- 

 about this union, which would be for the good and 

 progress of science in general? It is my prophecy, 

 says Dr. Negri, that these desires will very soon 

 become realised. John Milne. 



PROF. GEORGE CHRYSTAL. 

 n^HE lamented death of Prof. George Chrystal, of 

 -*- Edinburgh University, removes an outstanding 

 personality in academic and educational circles. 

 Aberdeen and Cambridge claim him as a distinguished 

 alumnus. In , 1875 he was bracketed with Prof. 

 Burnside as Second Wrangler and First Smith's 

 Prizeman. Even then he showed his leaning towards 

 applied rather than pure mathematics ; for Prof. Tait. 

 who was one of the examiners, used to say that 

 Chrystal excelled all the others in the way in which 

 he solved physical problems. 



After two years as professor of mathematics in St. 

 Andrews University, Prof. Chrystal in November, 

 1879, began his life's work as occupier of the like 

 chair in Edinburgh. The nature of his work com- 

 pelled him to give his best mind to the teaching of 

 mathematics and the training of the mathematical 

 teacher. In those days every student of arts had to 

 graduate in the same seven subjects. There were no 

 options. Even the comparatively mild problem- 

 solving mathematics of the old school, of which 

 Kelland had been a shining light, had made many a 

 man of classical and philosophical attainments tremble 

 as he entered the examination hall and sat down to 

 tackle the algebra or the Euclidean geometry paper. 

 But the first year of Chrystal's professoriate struck 

 terror to their hearts. Keen, rapid, logical, full of 

 sugi^csf ions' as to higher fields of mathematical de- 

 lights, ( Inystal transformed the whole atmosphere 

 of the class-room. Engrrly the mathematical minds 

 followed his fascinating^ Icul; despondingly ;ind 

 despairingly those not so gifted fell hopelessly behind, 

 faintly perceiving, if at all, the finely knit sequence 



