290 



NATURE 



\yan. 24, 1884 



tion of Aphides ; on the biology and morphology of 

 Aphides; on the antiquity of the Hemiptera, and par- 

 ticularly with regard to the Aphidinje as represented in 

 the sedimentary rocks and in amber; diagnoses of the 

 Aphides found in amber are given, with figures ; and we 

 have also an account of those known to occur in a fossil 

 state in America. Directions for the mounting and pre- 

 servation of Aphides are given, and we find a very com- 

 plete bibliography of authors who have treated about 

 Aphides, and a very excellent general index. 



In conclusion it only remains for us to congratulate the 

 author on the very successful accomplishment of this 

 important work, which is certain to excite an interest in 

 this marvellous group of insects, and the Ray Society on 

 being the medium of publishing the most beautifully 

 illustrated work on the Aphides that has as yet appeared. 



EARTHQUAKES AND BUILDINGS 



A COMPLETE discussion of the effects which earth- 

 -^*- quakes produce upon buildings would form a 

 treatise as useful as it would be interesting. Not only 

 would it involve a discussion of the practical lessons to 

 be derived from the actual effects of earthquakes, but it 

 would include deductions based on our present knowledge 

 of the nature of earthquake motion. Such knowledge is 

 obtained from the records of seismographs. 



In the following few notes I intentionally overlook this 

 latter portion of the subject, and confine myself to a few 

 ol the more important practical conclusions respecting 

 the effect of earthquakes on buildings, which may be of 

 value to those whose mission it is to erect buildings in 

 earthquake countries. 



With regard to the situation of a building, it is 

 sometimes observed that after an earthquake it is 

 the portion of a town situated on low ground which has 

 principally suffered, whilst adjoining portions on hills 

 may have practically withstood the disturbance. In 1855 

 this was the rule governing the distribution of ruin in 

 Tokio. The reverse, however, has been the rule in 

 Yokohama. Speaking generally on this point it may 

 be said that there is no universal rule, — each small area 

 in an earthquake region having its special rule. As a 

 site for a building, theory seems to indicate that soft earth 

 or marshy ground, which would absorb much of the 

 momentum communicated to it, and therefore act as a 

 buffer between a building and a shock approaching 

 through other strata, would prove a safe foundation. 

 This seems also to have been an old opinion, for we read 

 that the temple of Diana was built on the edge of a marsh 

 to ward off the effects of earthquakes, but experience has 

 repeatedly shown us, as in the case of Tokio and Manila, 

 that swamp-like ground, as an earthquake palliative, 

 has but little effect. On the other hand, hard rocky 

 strata, where the amplitude of motion is small, but the 

 period quick as compared with the motion in the inelastic 

 material of the plains, has, as was markedly illustrated in 

 1755 at Lisbon, and in 1692 at Jamaica, proved the better 

 foundation. Places to be avoided are the edges of cliffs, 

 scarps, and cuttings. For emergent waves, these are free 

 surfaces, and from their faces materials are invariably 

 shot off, much in the same way that the last car in an 

 uncoupled train of carriages may be shot forward by an 

 engine bumping at the opposite end. 



As foundations for a building there are two types. In 

 one, which is the European method of building, the 

 structure is firmly attached to the ground by beds of 

 concrete, brick, and stone. In the other, which is illus- 

 trated in the Japanese system of building, the structure 

 rests loosely on the upper surface of stones or boulders. 

 As an indication of the relative value of these two forms 

 of building, it may be mentioned that in Yokohama, in 

 1S80, many of the European buildings were more or less 



shattered, whilst in the Japanese portion of the town 

 there was no evidence of disturbance. 



The houses, like the foundations, are also of two types. 

 In the European house built to withstand earthquakes, 

 of which there are examples in Tokio and San Francisco, 

 and for which in America patents have been granted, we 

 hare a building of brick and cement bound together with 

 hoop iron and numerous tie rods. A building like this, 

 which from time to time is jerked backwards and for- 

 wards by the moving earth, to which it is secured by the 

 firmest of foundations, is expected to resist the suddenly- 

 applied and varying stresses to which it is exposed by the 

 strength of its parts. This type of structure may be 

 compared to a steel box, and it its construction involves 

 any principle, we should call it that of strength opposing 

 strength. Some of the buildings in Caraccas, which are 

 low, slightly pyramidal, have flat roofs, and which are 

 bound along their faces with iron, belong to this order. 

 These so-called earthquake-proof buildings, with the ex- 

 ception of their chimneys, have certainly satisfactorily 

 withstood small earthquakes in Japan. As to how they 

 would withstand a disturbance like that at Casamicciola 

 is yet problematical. LTnfortunately these structures are 

 very expensive. 



The second type of building may be compared to a 

 wicker basket. This is certainly as difficult to shake 

 asunder as the steel box type, and at the same time is 

 not so expensive. The Japanese house belongs to this 

 type. It is largely used on the west coast of South 

 America; and in Manila, since the disaster of 1S80, 

 it has rapidly been replacing the heavy stone form of 

 structure. Briefly, it is a frame house with a light roof 

 of shingle, felt, or iron. As put up in Japan, its stability 

 chiefly appears to depend on the fact that it is not firmly 

 attached to the earth on which it rests, and that its 

 numerous joints admit of considerable yielding. The 

 consequence is that, whilst the ground is rapidly moving 

 backwards and forwards, the main portions of the build- 

 ing, by their inertia and the viscous yielding of their 

 joints, remain comparatively at rest. 



A house that my experience suggests as being aseismic, 

 and at the same time cheap, would be a low frame build- 

 ing, with iron roof and chimneys supported by a number 

 of slightly concave surfaces resting on segments of stone 

 or metal spheres, these latter being in connection with 

 the ground. Earthquake lamps, which are extinguished 

 on being overturned, would lessen the risk of fire, while 

 strong tables and bedsteads would form a refuge in case 

 of sudden disturbances. 



In earthquake towns the streets ought to be wide, and 

 open spaces should be left, so that the inhabitants might 

 readily find a refuge from falling buildings. Brick chim- 

 neys running through a wooden building, unless they 

 have considerable play and are free from the various 

 portions of the building, are exceedingly dangerous. In 

 consequence of the vibrational period of the house not 

 coinciding with that of the chimney, the former by its 

 sudden contact with the latter when in an opposite phase 

 of motion almost invariably causes an overthrow. In 

 iSSo nearly every chimney in the foreign settlement in 

 Yokohama was overthrown in this manner, and the first 

 alarm inside the houses was created by a shower of bricks 

 falling on beds and tables. Since this occurrence the 

 chimneys in Yokohama have had more or less play given 

 to them where they pass through the roofs. 



Chimneys with heavy tops, like heavy roofs, must be 

 avoided. Another point requiring attention is the pitch 

 of a roof. If this is too great, tiles or slates will be readily 

 shot off. Archways over openings should curve into their 

 abutments, otherwise, if they meet them at an angle, 

 fractures are likely to be produced. 



If for architectural reasons, or as a precaution against 

 fire, it is necessary to have buildings which are sub- 

 stantial, their upper portions ought [to be as light as is 



