March 5, 1885] 



NA TURE 



417 



systematic inquiry into the sanitary situation of the country, 

 which was highly approved of at the Health Exhibition in 

 London, and now it has been determined to continue the inves- 

 tigations on a systematic and permanent basis. The members of 

 the Society scattered over Belgium are called on to assist in the 

 new undertaking, and the specimen forms which they are required 

 to fill in monthly are now before us. There are thirteen zones, 

 each zone being subdivided into districts. The physicians who 

 are members of the Society, or who are willing to participate in 

 its labours, are requested to state the diseases of which patients 

 in their practice have died during the month. From these 

 various reports a general statement, and tables of relative statistics 

 are issued by the central body. In course of time a medical 

 topography of the country, the enormous public advantages of 

 which are apparent, will be issued. 



The Transactions of the Seismological Society of Japan for 

 1884 (vol. vii. part 2) contains a paper, by Prof. Milne, on 387 

 earthquakes observed during two years in North Japan. To 

 determine the extent of country over which an earthquake was 

 felt, he distributed bin. dies of post-cards to the Government 

 officials at all important towns within a distance of loo miles of 

 Tokio, with a request that every week one of the cards should 

 be posted with a note of any earthquakes that might have 

 occurred. By this expedient it was discovered that the Hakme 

 Mountains to the south of the Tokio plain appeared to stop 

 every shock coming from the north, and accordingly the barrier 

 of post-cards was stopped in that direction, but was extended 

 gradually to the north until it included the forty-five principal 

 towns in the main island to the north of Tokio, besides several 

 places in Yezo. In Tokio, observations as to direction, velocity, 

 and intensity were made with various earthquake instruments. 

 A description of the principal instruments used, with a com- 

 parison of their relative merits, has already been given by Prof. 

 Milne in vol. iv. of the Transactions of the Society. The second 

 part of the paper is devoted to a list of the 387 earthquakes 

 recorded, with particulars of each ; 124 maps of earthquake dis- 

 tricts, as well as numerous other illustrations, are appended. 

 The results of an exhaustive study of these earthquakes may be 

 summed up as follows : — (1) As to distribution in space : of the 

 387 shocks, 254 were local, that is, they were not felt over an 

 area greater than 50 square miles ; 198 of these were confined 

 to the seaboard, and 56 were inland. The average diameter of 

 the land surface over which the remaining 133 extended was 

 about 45 miles, but four or five of them embraced a land area 

 of about 44,000 square miles. These great shocks originated 

 far out at sea, and consequently were not so alarming in their 

 character as many which originated nearer to or beneath the 

 land. (2) Simultaneous shocks : some of the disturbances took 

 place at areas remote from each other, whilst intermediate 

 stations did not record them. (3) Origins of earthquakes : the 

 general result under this head is that the greater number of 

 earthquakes felt in Northern Japan originated beneath the 

 ocean ; 84 per cent, of the » hole having so originated. The 

 district which is most shaken is the flat alluvial plain around 

 Tokio. Indeed, the large number of earthquakes felt in low 

 ground as compared with the small number felt in the mountains 

 is very remarkable. It is also noticeable that in the immediate 

 vicinity of active or recent volcanoes seismic activity has been 

 small. The map marking the general distribution of volcanoes 

 and the regions of the greatest seismic activity shows that these 

 are not directly related to each other. The district, too, where 

 earthquakes are the most numerous, is one of recent and rapid 

 elevation, and it slopes down steeply beneath an ocean which, 

 at 120 miles from the coast, has a depth of about 2000 fathoms, 

 whilst on the other side of the country, where earthquakes are 

 comparatively rare, at the same distance from the shore the 

 depth is only about 120 fathoms. In these respects the seismic 



regions of Japan resemble those of South America, where the 

 earthquakes also originate beneath a deep ocean, at the foot of 

 a steep slope, on the upper parts of which there are numerous 

 volcanic vents, whilst on the side of this ridge opposite to the 

 ocean earthquakes are rare. (4) Relation of earthquakes to 

 various natural phenomena : the preponderance of shocks in 

 winter, as revealed by this investigation, is really remarkable ; 

 278 took place in the winter months, as against 109 in the 

 summer, and of the former number, 195, or more than half of 

 the whole number for the two years, took place in the three 

 coldest months of the year — viz. January, February, and March, 

 in other words, there is a general coincidence between the maxi- 

 mum of earthquakes and the minimum of temperatures. But 

 the relation of seismic intensity (as distinct from the number of 

 earthquakes) is even more remarkable, for the figures show that 

 the winter intensity is nearly three and a half times as great as 

 the summer intensity. M. Perrey thought he discovered a 

 maximum of earthquakes for the moon's perigee, but no such 

 maximum has been found for Japan. Speaking generally, no 

 marked coincidence was found in the present instance in the 

 occurrence of earthquakes and the phases of the moon. The 

 above are the general results, stated briefly, of the most ex- 

 haustive and remarkable study yet undertaken in the domain of 

 seismology. 



La Nature contains a long report on the Andalusian earth- 

 quakes, from the pen of M. Nogues, a mining engineer of 

 Granada, which, as being the first scientific investigation of 

 the catastrophe, is worthy of special notice. The whole move- 

 ment presented three phases. The first manifested itself, prior 

 to December 25, at Pontevedra, Vigo, and in Portugal ; in other 

 words, in the eastern part of the Iberian peninsula. The second 

 was very short and intense, and made itself felt in the centre 

 and south ; it reached its maximum intensity on the night of 

 December 25. The third phase lasts still in the provinces of 

 Granada and Malaga, and extended east to Valencia. The 

 oscillatory movement of December 25 embraced a considerable 

 superficial extent. The disturbed area in the peninsula is com- 

 prised between Cadiz and Cape Gaeta, between Malaga and the 

 Carpetena chain. The movement became more and more 

 intense as it left this mountainous mass and travelled in a 

 southerly direction, until it attained its maximum in the region 

 between the Serrania de Ronda and the Sierra Nevada of 

 Granada. The oscillatory motion was gradually accentuated 

 towards the south, especially on the southern side of the great 

 central Spanish plateau, bounded by the slope of the valley of 

 the Guadalquivir (Seville, Cordova, Malaga, and Granada). 

 M. Garcia Alvarez localises the phenomenon in Andalusia, and 

 regards the Sierra Nevada as the point of departure. M. 

 Nogues then deals in succession with the relations between the 

 seismic motions and the geological structure of the district, the 

 geological phenomena, such as fissures in the earth, produced 

 by the earthquakes, and alterations caused by them in the level 

 of springs. He sums up his conclusions by pointing out that 

 the geological observations which have been made so far, 

 although local, limited, and imperfect, demonstrate that there 

 were two different kinds of motions— one oscillatory, the other 

 a trembling movement. Every one who felt the great earth- 

 quake of the 25th experienced first a vertical shock, and then, 

 after a short interval, another movement like a balancing. A 

 great fissure at the village of Guevejar presents at two points 

 two interesting sections. At one the trunk of an olive-tree has 

 been split in t*o from its root to the branches, as if from a blow 

 of a hatchet, each part occupying a side of the fissure, one on 

 one side, the other on the other. At another part the fissure 

 has divided in two the wall supporting the wheel of the powder- 

 factory at Guevejar. The cracks in the houses in the village are 

 in lines parallel to these fissures, and the marks left in the soil 



