December io, 1891] 



NA TURE 



127 



SEISMOMETRY AND ENGINEERING IN RE- 

 LATION TO THE RECENT EARTHQUAKE 

 IN JAPAN. 



A T 6.38 a.m. on October 28, I was awakened at my 

 •^*- house in Tokio by the long swinging motion of an 

 earthquake. There was no noise of creaking timbers, 

 and there were no shocks such as usually accompany 

 earthquakes. It was an easy swing, which produced 

 dizziness and nausea. As recorded by bracket seismo- 

 graphs this continued for ten or twelve minutes. During 

 the interval there was ample time to study the movements 

 of these instruments, and the conclusion that could not 

 be avoided was that rather than acting as steady points 

 these heavy masses were simply being swung from 

 side to side — horizontal displacement was not being 

 measured, but angles of tip were being recorded. That 

 many of our seismographs are useless as recorders of 

 horizontal motion whenever a vertical component of 

 motion is recorded, is a view that I have held for many 

 years, and therefore when these two have been recorded 

 in conjunction I have been inclined to receive the records 

 with caution. 



Further, the measurement of vertical motion as recorded 

 by a horizontal lever arrangement can only be trusted if 

 we can assure ourselves that the advance of the waves 

 has been at right angles to the direction of the lever. If 

 this condition is not fulfilled, then the seismograph for 

 vertical motion may also become a tip-recording instru- 

 ment. As another indication that during this particular 

 earthquake earth tips occurred, I may mention that the 

 water in a tank with perpendicular sides which is about 

 25 feet deep, 60 feet long, and 30 feet broad, rose quickly, 

 first on one side and then on the other, to a height of 

 3 or 4 feet — much in the same way that water would 

 rise and fall in a basin that was being tipped from side 

 to side. 



Assuming what is said to be correct, it must not be 

 concluded that modern seismographs are useless. For 

 earthquakes where the motion is horizontal, they give 

 records which practically are absolutely correct. When 

 vertical motion occurs, in many cases if not in all, the 

 records must be interpreted in a new light. The so-called 

 horizontal displacements may be employed in determining 

 the maximum slope of a wave, and if from an instrument 

 recording vertical motion we are assured that we have 

 measured the vertical height of a wave, we can at least 

 approximate to the length of the same. The period of 

 the waves being recorded, it follows that the velocity of 

 propagation may be calculated. 



Although it seems possible to use our present bracket 

 seismographs as angle measurers, it is evident that there 

 are other types of instruments, where swing due to inertia 

 is minimized, which will act more satisfactorily. To 

 obtain a true measure of vertical displacement, the most 

 evident solution would be to use a number of lever 

 arrangements in different azimuths. Other methods may, 

 however, suggest themselves. 



For the present our time is too much occupied with 

 outside observations to attend to instruments or to reduce 

 their records. Up to date it is known that nearly 8000 

 people have been killed, many having been consumed in 

 the burning ruins where they were entombed. At least 

 41,000 houses are level with the plain, and engineering 

 structures which have stood both typhoon and flood have 

 been reduced to ruin. In the middle of the stricken 

 district, which is near Gifu and Ozaki, it is doubtful 

 whether any ordinary building could have resisted the 

 violence of the movement ; but outside this, much de- 

 struction might have been obviated had attention been 

 given to the ordinary rules of construction, and to the 

 special rules formulated by those who have considered 

 the question of building in earthquake countries. In 

 many places so-called " foreign " buildings of brick and 



NO. II 54, VOL. 45] 



stone— undoubtedly put up in the flimsiest manner — lie- 

 as heaps of ruin between Japanese buildings yet stand- 

 ing. Cotton mills have fallen in, whilst their tall brick 

 chimneys have been whipped oft" at about half their height. 

 Huge cast-iron columns, which, unlike chimneys, are 

 uniform in section, acting as piers for railway bridges, 

 have been cut in two near their base. In some instances 

 these have been snapped into pieces much as we might 

 snap a carrot, and the fragments thrown down upon the 

 shingle beaches of the rivers. The greatest efforts 

 appear to have been exerted where masonry piers carry- 

 ing 200-feet girders over lengths of 1800 feet have been 

 cut in two, and then danced and twisted over their solid 

 foundations considerable distances from their true posi- 

 tions. These piers have a sectional area of 26 x 10 feet, 

 and are from 30 to 50 feet in height. Embankments have 

 been spread outwards or shot away, brick arches have 

 fallen between their abutments, whilst the railway line 

 iiself has been bent into a series of snake-like folds and 

 1 ummocked into waves. The greatest destruction has 

 taken place on the Okazaki-Gifu plain, where we have 

 nil the phenomena— like the opening of crevasses, the 

 spurting up of mud and water, the destruction of river 

 b inks, &c.— which usually accompany large earthquakes. 

 At Okazaki and Nagoya the castles have survived. The 

 reason for this may be partly attributable to the better 

 class of timber employed in their construction, but 

 principally to their pyramidal form and to the fact that 

 they are surrounded by moats. Here and there a temple 

 has escaped destruction, partly, perhaps, on account of 

 the quality of materials employed in its construction, 

 but also in consequence of the multiplicity of joints 

 which come between the roof and the supporting columns. 

 At these joints there has been a basket-like yielding, and 

 the interstice of the roof has not, therefore, acted with its 

 whole force in tending to rupture its supports. On 

 the hills which surround the plain, although the motion 

 has been severe, the destruction is not so great. These 

 hills are granites, palaeozoic schists, and other rocks. 

 There is nothing volcanic. In the small cuttings where 

 the railroad passes from the hills out into the plain, no 

 effects of disturbance are observable, the surface motion 

 probably having been discharged at the faces of the 

 inclosing embankments. The general appearance out- 

 side the cuttings, however, is as if some giant hand had 

 taken rails and sleepers and rubbed them back and forth 

 until the ballast lying between them was formed into 

 huge bolster-like ridges. Crossing the hills and proceed- 

 ing to other plains, it is noticeable that there has been 

 more movement on the alluvium than on the rocks. 



Earthquakes yet continue, and in the Gifu plain each 

 one is preceded by a boom as if a heavy gun had been 

 fired in some subterranean chamber. Although the sur- 

 vivors, who may number, perhaps, two millions, are, 

 for the most part, destitute, have witnessed the most 

 terrible scenes, and are yet surrounded by the dead 

 and the dying, yet there is no panic. They hear a 

 " boomb," and run laughing to the middle of the street 

 to escape the shock which the unaccountable noises 

 herald. The Japanese have their feelings, but on oc- 

 casions of this sort there is no helplessness in conse- 

 quence of hysteria or mental prostration. As to what 

 happens with Europeans under like circumstances, I 

 must leave readers to consult history. 



John Milne. 



Tokio, November 7. 



FURTHER RESEARCHES UPON AZOhMIDE^ 

 N3H. 



'X*HE discovery of this remarkable compound of hydro- 



•»• gen and nitrogen by Prof. Curtius, in the chemical 



laboratory of the University of Kiel, formed one of the 



