6o4 



NA TURE 



[April 29, I i 



occasion before long to communicate to you tlie general results 

 of all observations made during past years. 



An equally interesting set of observations carried out by the 

 Meteorological Bureau was the determination of areas shaken 

 in every earthquake, together with the reductions of results during 

 the years 1885-86 — the works of which I was directed to super- 

 intend. The method followed out was almost exactly the same as 

 that originated by Prof. J. Milne in studying "387 earthquakes 

 in North Japan," an epitome of which appeared some time ago 

 in your columns. This method is briefly as follows. Observa- 

 tion-books furnished with directions for reporting earthquake 

 phenomena with or without instruments were distributed, au- 

 thorised by Government, among over 600 local offices through- 

 out the empire ; in fact, the earthquake observations were made 

 a part of the duty of local officers, and the reports were trans- 

 mitted free of postage. From the reports sent in by different 

 observers thus closely stationed, maps have been made showing 

 the disturbed area in every shock, and a summary of observations 

 has been compiled. 



The results worked out from a large number of these maps 

 and their notes have revealed many interesting facts, and entirely 

 confirmed the previous works of the eminent seismologist above 

 mentioned. 



The total number of earthquakes in Japan in 18S5 was 482, 

 equivalent to 1-3 shakings a day. In Tokio alone 68 shocks 

 were registered. Earthquakes are most prevalent in Yezo, and the 

 north and central portions of the main island along the eastern 

 or the Pacific coast, but in provinces bordering the Japan Sea 

 they are few, and in some places none at all ; if they occur, 

 they are generally limited to small tracts of land. .Speaking of 

 the main island in general, the range of mountains traversing 

 through and forming the backbone of Central Nippon appears 

 to divide it into two zones of different seismatic activities. In 

 Kiushu, Shikoku, and other islands, disturbances are compara- 

 tively small. 



Most larger earthquakes originate beneath the ocean. The 

 majority of shocks are only local. Of the whole number, 235 

 local disturbances were recorded, which have not extended more 

 than 100 square miles of land area. The maximum area oi one 

 earthquake was 34,700 square miles. The aggregate area of dis- 

 turbance during the year was 796,000 square miles, and taking the 

 total area of the empire to be 147,000 square miles, it is equivalent 

 to saying that the whole of Japan has been shaken 5-4 times in one 

 year. In summer shocks are less prevalent than in winter. The 

 earthquakes occur in groups, that is to say, when disturbances 

 occur, they are limited within certain portions of country, not 

 generally extending beyond these limits. Propagations of seismic 

 waves are often stopped by mountain-chains. 



Finally, I may state that we shall continue these observations 

 in future, and I hope the results to be obtained from more years' 

 work of this nature will be some help in throwing light on the 

 physics of the earth's crust. Seikei Sekiya 



The Imperial University of Tokio, Japan, February 28 



Pumice on the Cornish Coast 



Is Mr. Guppy sure that the "pumice " he records in Nature 

 for April 15 (p. 559), as found on Maenporth Beach, is the 

 natural article ? I ask because of having been accustomed to 

 find pieces of a pumice-like stone, many light enough to float on 

 the sea, along the Suffolk coast. This, however, is an artificial 

 product, a sort of cinder from steamers, though it has deluded 

 many people. It puzzled me for some time. 



\V. Whitaker 



$1, East Park Terrace, Southampton 



Ferocity of Animals 



If your correspondent in last week's NATURE (p. 5S3) will 

 treat a wild rat in the way which I described, the animal will 

 answer his question much more effectually than I can. For 

 while I have only words at my dispisal whereby to convey any 

 "ejective" information upon the subject, the rat will display 

 the fact of his understanding your correspondent's intention 

 by a thousand co ordinated movements of a much more eloquent 

 kind. 



The paper by Mr. Lloyd Morgan in the current issue of Mind 

 is merely a republication of his views as already presented in 

 this periodical. Having replied to these views as fully as seemed 

 to me desirable when they were first expressed, it is needless 

 that I should now go, over the same ground a second time. It 

 will, therefore, be sufficient to refer your correspondent to the 

 discussion between Mr. Morgan and myself, which he will find 

 in consecutive issues of Nature for February and March 1884. 

 George J. RoMA^ES 



The Climbing Powers of the Hedgehog 

 I rememrer many years ago we kept a hedgehog on the 

 Continent in an upper garden well \i ailed in. There she re- 

 mained for some time, until she littered four or five young in a 

 rubbish heap in a corner. The young having grown, and being 

 able to move about, she and her whole brood disappeared. Her 

 only way was over a wall four or five feet high, on which she 

 left traces, but the young could not have been able to climb 

 this, and she must have carried them. Hyde Clarke 



32, St. George's Square, S. VV. 



ON THE LA IV OF THE RESISTANCE OF THE 

 AIR TO THE MOTION OF PROJECTILES 



IN my experiments made to determine the resistance of 

 the air to the motion of projectiles, it was assumed 

 that this resistance followed souie law producing a 

 gradual change in the velocity, and consequently that 

 the times occupied by the shot in passing over a succes- 

 sion of ecjual spaces would admit of being differenced. 

 This method of proceeding gave the required result in 



"The Krakat.ib Dust-Glows of 1883 84" 



In your issue of March 25 (p. 4S3) the writer of the critical 

 notice of Dr. Riggenbach's pamphlet on the above propounds a 

 statement which, if true, is of vast importance in accounting for 

 the subsequent optical phenomena which are supposed to have 

 been connected with the eruption. He says : " Thus the hurl- 

 ing into the air of 150 cubic kilometres of volcanic dust in August 

 18S3," &c. Whence does he deduce this enormous quantity ? 

 M. Verbeek, in his " Krakata"b," part I, which I have carefully 

 perused, estimates the entire volume of ejecta (chiefly based on 

 what fell near the spot) at only 18 cubic kilometres, and as his 

 work is the only reliable source of information regarding the 

 eruption with which I am acquainted, I am entirely at a loss to 

 conceive how the 18 has been suddenly magnified into 150. 



.\s one of the Krakata"o Committee of the Royal Society, I 

 have naturally examined the theoretical possibility of the amount 

 of dust ejected having been sufficient to account for the optical 

 l>henomena w^itnessed, and have been obliged to content myself 

 with the very modest quantity of 4 cubic kilometres out of the 

 total 18, but if your writer's statement is correct, I am evidently 

 at liberty to considerably augment the quantity at my disposal, 

 and it is needless to say that this would seriously change the 

 aspect of the question. E. Douglas Archibald 



April 15 



the form of a coefficient A': of 7'^, in terms of the second 

 and higher differences of time above referred to, when 

 the time was expressed in seconds to five places of 

 decimals. So long as this value of K remains constant, 

 the resistance of the air varies as the a/lh' of the velocity 

 The first results obtained were published in a note in the 

 Phil. Trans, for 1868, p. 441. The experiments were 

 afterwards more carefully calculated, and given in detail 

 in the Reports published by Government in 1870. In 

 using these results to calculate general tables for space 

 and time, for cases where the projectile could be supposed 

 to move approximately in a straight line, and free from 

 the action of gravity, the corrected mean values of A',, were 

 used, and made to vary with the corresponding velocity v. 

 And in my ''Treatise on the Motion of Projectiles" (1873), 

 the cubit: law of resistance was used for the purposes of 

 calculation, so that for those velocities where I\ varied it 

 was necessary to divide the trajectory into such small 

 arcs that, throughout each arc, the average value of K 

 could be used without sensible error. This treatment of 

 the question rendered it unnecessary for me to attempt to 

 express the law of resistance according to powers of z' for 

 all practical velocities. But from the results of my experi- 

 ments for velocities between 900 and 1700 f.s., I remarked 



