April i8, 1901J 



NA TURE 



589 



building materials, and investigated the effects of several 

 earthquakes upon tall chimneys. Dr. B. Koto has handed 

 to the committee twenty-two papers on geological subjects 

 connected with seismology and volcanology. Dr. H. 

 Nagaoka gives a paper of intense interest to all physic- 

 ists on the determination of the elastic constants of 

 rocks ; whilst the well-known professor of seismology, 

 Dr. F. Omori, contributes six papers, each of importance 

 to seismologists, and for the most part indispensable to 

 those who have to construct in earthquake countries. 



Volumes v. and vi., which contain the analysis of the 

 diagrams of 246 earthquakes observed in Tokyo between 

 July 1898 and December 1899, are entirely from Dr. 

 Omori's pen, and although we may not concur in all the 

 results he sets before us, seismologists in general must 

 thank him for the vast quantity of material which he has, 

 brought together and systematised for their consideration. 

 For the earthquakes which originated at great distances 

 from Japan, so far as possible each seismogram has been 

 divided into parts which succeed each other in the follow- 

 ing order : " First preliminary tremors," in which waves 

 of 4 seconds period are superimposed upon those of 8 

 seconds ; " second preliminary tremors," with periods of 

 8 seconds, and accompanied by undulations of 14, 25 

 and 66 seconds period ; "the principal portion " of the, 

 earthquake, which is divided into three phases also 

 dependent on period, and finally the " end portion," in 

 which period is fairly regular. The regularity of the 

 terminal vibrations may, as Dr. Omori remarks, be ex- 

 plained on the assumption that different portions of the 

 earth's crust have particular periods of free oscillation. 

 The discussion of these various types of earthquake 

 motion is based on the assumption that the waves 

 recorded are horizontal movements and not tiltings of the 

 ground. 



One observation which led Dr. Omori to take this view 

 is that he has obtained seismograms which show that the 

 amplitude of motion depends upon the multiplication 

 ratio of the writing pointers attached to his pendulums, 

 and not upon their sensibility to tilting. In addition to 

 this he points out that if the undulations recorded were 

 due to tilting, then the accelerations involved are such that 

 our sense of feeling should be affected, which is not the 

 case. Since Dr. A. Cancani, in 1893, drew attention to 

 the fact that calculations based on a knowledge of the 

 period, velocity and maximum tiltings of these unfelt 

 undulations led to the conclusion that the inhabitants 

 of the world were raised and lowered two or three feet 

 hundreds of times per annum and had never observed 

 the same, seismologists have regarded with suspicion 

 the elements in the calculations leading to these results. 

 Notwithstanding this, when we have so very much 

 evidence of turbulent wave-like motion in and around 

 epifocal districts, and evidence of repeated tiltings at 

 distances of several hundred miles from the same, it is 

 difficult to escape from the conclusion that similar but 

 slower period movements may be propagated, like a swell 

 upon an ocean, to very distant places, and seismographic 

 pendulujns be caused to swing. 



■_ Dr. Omori has certainly thrown new light upon the 

 nature of the large waves, and it does not seem impro- 

 bable that investigations carried out upon other lines 

 may, if not completely at least partially, confirm his 

 views. 



A more debatable subject touched upon relates to 

 paths followed by earthquake waves through the earth's 

 crust. Because the velocity of the quick period phase of 

 the large waves nearly equals that of local earthquakes, 

 it is assumed that the former, like the latter, are propa- 

 gated along the surface of the earth's crust, whilst 

 waves which precede them travel at some small depth 

 in the same. Inasmuch as the first preliminary tremors 

 have, at a given station, a duration proportional to the 

 arcual distance of this station from the origin of the 



NO. 1642, VOL. 63] 



earthquake. Dr. Omori thinks it likely that they are 

 transmitted along paths nearly parallel to the surface of 

 the earth, and at a probably constant depth. 



Several sections in vol. v. refer to subjects which are 

 not seismic, although they are of great interest to those 

 engaged in certain branches of physical research. For 

 example, references are made to the effect of slight loads 

 upon masonry structures, whilst " oscillations of the 

 ground," whose origin is not seismic, are discussed at 

 some length. That we have for years past been ac- 

 quainted with movements of pendulums and balances not 

 proper to those of the instruments themselves, which 

 may continue for hours or days, suggests the question 

 whether we are not here being re-introduced to an old 

 enemy in a new dress. Are these movements due to 

 those of the ground or to local movements in the atmo- 

 sphere ? Can Dr. Omori assure us that similar instru- 

 ments, placed in different rooms or under conditions 

 which are different with regard to temperature and 

 ventilation, behave similarly ? If this be the case, then 

 the distinction which has so frequently been drawn 

 between "pulsations" and "air tremors " will be more 

 clearly established. In a stable at Shide " air tremor "' 

 effects are, at certain seasons, frequent, whilst at times 

 pendulums with a 15 seconds period will yield diagrams 

 showing that they have been moving regularly with a 

 period of two or three minutes. In an adjoining coach- 

 house these movements are absent, and similar pheno- 

 mena are common to Tokyo and other places. 



What has here been said indicates the nature of the 

 work now in progress in Dai Nippon, a complete account 

 of which is to be found in thirty-two well-illustrated 

 quarto volumes, which, unfortunately for Europeans, are 

 written in Chinese characters. These volumes are with 

 but little doubt one of the greatest store-houses extant of 

 information relating to practical seismology, and as such 

 it is to be hoped that an abstract, or at least a table, of 

 their contents may be published in a European language. 



As an example of their value we may select vols. xxii. 

 and XXV., referring to an earthquake which in 1897 

 devastated North-Eastern India, and cost British in- 

 vestors and taxpayers several millions sterling. The 

 first of these is by Dr. T. Nakamura, an architect, and 

 it contrasts those forms of structure which withstood 

 the effects of the earthquake with those which failed. 

 The second, which treats of railway and bridge con- 

 struction, is by Mr. T. Koyama, a railway engineer. 

 These gentlemen are two out of four who were sent 

 to India by their Government for the purpose of increas- 

 ing their own extensive knowledge as to forms of 

 structures most suitable for earthquake countries. On 

 this occasion, as in others, special men were selected 

 for special work, with the result that, not only has Japan 

 profited by disasters of this character, but she has 

 become a teacher of nations in practical seismology, 

 and we, amongst others, may offer her thanks and 

 congratulations on her efforts to save life and property. 



J. Milne. 



THE EYE IN THE RECENTLY DISCOVERED 

 CA VE SALAMANDER OF TEXAS} 



THE tailed Batrachia have during recent years 

 attained an increased importance zoologically, by 

 appreciation of the fact that in respect to many features 

 in which their living representatives present a simplifica- 

 tion of organisation they are retrograde. While but one 

 of them possesses a complete maxillo-jugal arch, none 

 are pentadactyle in both fore- and hind-limbs ; and the 

 unexpected has been reached, in the discovery that there 



l"The Eyes of the Blind Vertebrates of North Am-irica," by C. H. 

 Eigenmann {Trans. Americ. Microsc. Soc., vol. xxi. pp. 49-60), by C. H. 

 Eigenmann and W A. Denny {Biological Bulletin, Boston, U.S.A., vol. u. 

 pp. 33-40) 



