Dec. 29, 1887] 



NATURE 



201 



Siberian rivers make no deposit, either in winter or summer, 

 which could cover in a mammoth. Nor are the mammoths 

 chiefly found near rivers, but on high ground out of the reach of 

 rivers. When they occur near the rivers, it is generally on the 

 head streams, which could not float such carcasses. 



Surely, in criticizing my view of a problem which has been 

 the crux of almost every serious student since the days of Cuvier, 

 your critic might have noticed these now elementary facts. It 

 is not fair to me or to your readers to deal with this difficult 

 question as if it could be settled by a casual reference to causes 

 long ago discarded by such authorities as Brandt and Baer, 

 Schmidt and Schrenck. 



I am anxious beyond measure to meet with some criticism 

 that I can reply to, and shall not shrink from the issue being 

 tried by the severest tests. 



What I complain of, and others more important than myself 

 share my opinion, is that the only answer forthcoming from uni- 

 formitarians to test cases like the one above referred to is, 

 ostrich-like, to put their heads in the sand and to cry out, 

 " Since we are committed to Lyell's theory, it is useless to 

 quote facts against us." This may have done in the fifteenth 

 century, but it will not do now when so many critics are abroad. 



May I presume to invite a discussion in your paper on this 

 most interesting question? I cannot forget that it was in your 

 pages I first raised it many years ago. 



Bentcliffe, Eccles, December 10, Henry H. Howorth. 



In regard to the first part of Mr. Howorth's letter, I must re- 

 mind him that it was admitted in my review that such a being 

 as an irrational uniformitarian did exist, and was duly smitten 

 in his book. 



In regard to the occurrence of mammoth carcasses (not 

 skeletons), I wrote of ice with some hesitation, knowing alleged 

 cases to be open to question, but I mentioned it, because, in 

 my opinion, it would be the most difficult to explain, and the 

 strongest case in favour of Mr. Howorth. Where the carcass is 

 preserved in clay or gravel the difficulty is less. All that seems 

 needed is a flood of rather exceptional character, carrying the 

 dead beast rather far north ; then, if this happened at the right 

 season of the year, the body might be buried by other floods 

 before decomposition set in (the temperatures might be always 

 low, though sometimes above 32° F.), and so the body 

 might escape unrotted, until it was finally well entombed. My 

 position was that, though this explanation of the escape of a 

 carcass from destruction, under circumstances not very different 

 from the present, was not easy, the explanation of such a series 

 of catastrophes as Mr. Howorth demanded was much harder. 

 The grounds of this opinion cannot of course be stated in the 

 limits of a letter, nor can I discuss seriatim the cases which he 

 cites. So far as my memory serves me (I am writing at a 

 distance from any scientific library) they are not so universally 

 favourable to his view as is stated in his letter. 



The remainder of Mr. Howorth's letter is open to the charge 

 which he brings against the review, of being merely rhetorical. 

 Quis tulerit Gracchos de seditione querentes ? 



Your Reviewer. 



Centre of Water Pressure. 



The following extremely simple construction for the centre of 

 pressure of a homogeneous liquid on a triangular area occupying 

 any position whatever in the liquid has not (I learn from a high 

 authority on hydrodynamics) been hitherto known, and it may 

 be interesting to some of the readers of Nature. 



Let a particle be imagined to be placed at each vertex of the 

 triangle, its mass being proportional to the depth of this vertex 

 from the surface of the liquid ; let g' be the centre of gravity of 

 these particles, and let G be the " centre of gravity " of the tri- 

 angular area. Then P, the centre of pressure, lies on the line 

 G g' at a distance J G g' from G. 



There is another almost equally simple way of expressing this 

 result ; and of course it is known that there are other ways, more 

 or less practically unmanageable, of representing the position of 

 this point, p, by means of momental ellipses, &c. 



George M. Minchin. 



R.I.E. College, Cooper's Hill, December 15. 



The Recent Earthquakes in Iceland. 



On October 28 last, at 20 minutes past 5 in the morn- 

 ing, two earthquakes occurred at Reykjavik, and reports were 

 soon received as to earthquakes in other districts, especially at 

 Cape Reykjanes. The whole peninsula of Reykjanes is covered 

 with lava streams, and there are many craters and fissures. The 

 extreme point of this peninsula seems in former times to have 

 been the scene of many volcanic eruptions. Tradition tells that 

 long ago the promontory stretched eight miles further to south- 

 west than it does now, and that great earthquakes and volcanic 

 eruptions in the years 1389-90 produced the subsidence of the 

 ancient promontory. The land reached then to Eldey (the Fire 

 Island), or, as the Danes call it, " Melsjekken." In historic 

 times ten volcanic eruptions are known to have taken place in 

 the neighbourhood of these rocks. 



During the night between October 27 and 28 more than forty 

 shocks were felt at the lighthouse of Cape Reykjanes, nine of the 

 lamps were broken, and the house where the lighthouse keeper 

 lives and a warehouse were damaged. A fissure from south- we.' t 

 to north-east was formed in the rocks 2 yards from the light- 

 house ; the rocks beneath were cracked in several places, and 

 these cracks go in the same direction as the old fissures asso- 

 ciated with volcanic cones. At Eyrarbakki the earthquake was 

 observed at 25 minutes past 5, and proceeded from north - 

 north-west to south-south-east. To north-west the earth- 

 quake was felt in Borgar fjord, and as far to the south-east as to 

 Eyjafjoll. This shock was therefore felt over an area of more 

 than 4500 square miles. 



A less violent earthquake was felt here in Reykjavik on 

 November 13, at 35 minutes past 9 p.m. 



In the year 1882 I published in an Icelandic review, Andvari, 

 a list of questions concerning earthquakes, nearly the same as 

 were published in 1880 by Prof A. Heim for the Earthquake 

 Commission in Switzerland. A similar list of questions has now 

 been printed in the Icelandic newspapers. The questions will 

 also be printed separately, and sent to Icelandic clergymen and 

 others who probably take interest in this subject. 



Reykjavik, November 30. Th. Thoroddsen. 



The Canary Islands. 



Now that the Canary Islands are rapidly becoming better 

 known as one of the most advantageous health-resorts within 

 easy reach of England, it may be of some interest to mention a 

 few facts concerning diseases in the Archipelago. 



The one pre-eminent fact is that the climate seems to modify 

 the virulence of the worst, the most dangerous diseases. 

 Puerperal fever, though rather prevalent, is seldom, I may 

 almost say never, fatal, though I know of cases where the 

 patient has been neglected for several days before medical advice 

 was obtained. Diphtheria is also very prevalent in the large 

 towns, owing to the total absence of the most ordinary sanitary 

 piecautions, but it seems always to exist in a mild form. I 

 know of certain families who apparently have it frequently, but 

 this terrible disease seems to be only fatal where the mo t 

 elementary knowledge of nursing is absent. 



Fevers of all kinds are lighter in character. The treatment 

 recommended there by the profession is different from thatinvogiu; 

 in England. For example, it starts by a thorough clearing out 

 of the system by means of somewhat violent purgatives and 

 emetics. 



Equable as is the climate by day and night, the natives suffer 

 most from chills, which often end fatally. This, I think, may 

 be in a great measure accounted for by the absence of woollen 

 or silken clothing. Those who visit the Canaries from colder 

 northern latitudes where wool is worn next the skin, and who 

 most wisely continue this habit, do not suffer in this way. It is 

 advisable that every article of clothing worn in the islands be 

 either made of wool or silk. Thus armed, one is almost im- 

 pregnable to the attacks of any disease of a catarrhal nature. 

 Malaria does not exist. Precautions as to hours of recreation, 

 such as keeping in the house at sundown, are in these islands 

 unnecessary, and one may be out on the hottest day at the hottest 

 hour without fear of sunstroke. 



The only disease which in any way can be said to be peculiar 

 to, or prevalent in, the Canary Islands is elephantiasis, which, 

 as your readers well know, does not affect well- nourished 

 inhabitants, and is neither contagious nor infectious. 



In Gran Canaria diseases of the stomach and intestines are 



