242 



NA TURE 



[Jan. 25, 1872 



from it in not being cusped, tliough otlierwise imitating its 

 general form. 



It would appear, therefore, as if a wedge-shaped film of water 

 were pushed ahead of the canoe, or other obs acle, the lower 

 suiface of which must, from the arrangement o( the particles 

 arrested, have been of rapidly-increasing curvature. Two diffi- 

 culties, however, present themselves to this explanation — it is 

 difficult to see how the film could have extended to the wave 

 itselt, as no particles, however small, appeared to be arrested 

 wiihin an inch or t^*'o of it ; and my rec Uection is that upon 

 the occasion of my fiist examining the wave driven helore my 

 canoe, 1 ghc objects merely testing up' n the water, like 

 thistle down, seemed to be not at all affected by it, but to pass 

 on towards the canoe unimpeded. Such objects, however, are so 

 easily affected by the wind, or ( ven the resistance of the air, that 

 it was not easy to verify the observation. 



Some other facts may be mentioned. The depth of the ob- 

 struc:ii/n in the water seemed to have no sensible effect on the 

 wave formed. Whether it was a log a foot through, or an 

 inch board floating on the water, or wheiher it was the mid- 

 dle of the canoe drawing five or six inches, or the bow and 

 stem barely touching the surface, the effect teemed almost 

 the same. I have olten, indeed generally, failed in my attempts 

 to generate a wave with a canoe, and although upon the occjsion 

 when I fiist saw it so formed, I could trace it at fully eight 

 feet from the canoe, I never found such a wave naturally 

 formed at anything like that distance. The explanation appears 

 to be that it requires very even and steady action to i;enerate the 

 wave ; but that wlen once established it can be maintained un- 

 der circumstances in which it would not be otherwise produced. 

 As I stated before, if you approach it in one direction, you may 

 take a canoe over it and it emerges on the other side unimpaired ; 

 the ii regular currents of an eddy have no etfect upon it except to 

 give it an undulating motion, and I have seen it maintaining its 

 place among^t the standing waves of a rapid when they have 

 been several inches high. 1 have even raised considerable swells 

 by rocking a canoe close to it, and it rides over them without 

 disturbance ; but the slightest ripple caused by the wind makes 

 it disappear in a moment ; and if spirits of turpentine be dropped 

 on the water a little above it, the whole wave is instantly oblite- 

 rated to a distance apparently far beyond that to which the oily 

 film extends. John L.\ngton 



Ottawa, Canada, Dec. 28, tSyi 



The Rigidity of the Earth 



Although, as he truly says. Sir W. Thomson's arguments 

 for the rigidity of the earth have never been attacked, yet they 

 have undoubtedly been too long ignored ; and it is gratifying to 

 see them asset ted by their author in Natltke. Allow me, 

 however, to remark on one sentence near the end of his quota- 

 tion fnim the "Natural Ph.losophy," where Mr. Hopkins's 

 observation is givrn, that the distr bution of fluirl matter within 

 the earth is " piobably quiie local." Unless I am mistaken, Mr. 

 Hopkins's opinion was, that its diStributi -n is, as one might say, 

 fortuitous. But, as I have elsewhere observed, the trains of 

 volcanoes which accnm^jany many of the great lines of elevation 

 for enormous distances re dcr ihe motion of such local distri lU- 

 tion of fluid matter highly improbnble, unless it be admitted that 

 its presence is due to mountain elevations as a cause. I have 

 suggested that this fluidity may arise from a dimini-hed piessure 

 beneath mountain range*, owing to their mass being partly sup- 

 ported by the literal thrust which has upraised them — a supposi- 

 tion which Mr. Scrope had already applied to account for an 

 incirased fluidity in the hea'ed rock underlying a volcanic vent, 

 when from any cause the prcs-ure became le^s. 



If any of your correspoiideuts can propose another explanation 

 of this remarkable coincidence compatible with the supposition 

 of a rigid globe, it would be interesting to know it. 



IlarUun, Cambridge O. Fisher 



English Rainfall 



In reply to the letter of Mr. "Vernon, in Nati7RE of the l8th 

 inst., permit me to say that the conru>ion between the two 

 Seaihwaites is his^ not jnine In th'* article to which he ref rs 

 theie IS not a word about either Cockley Bridge or the Valley of 

 tie Duddon. His topographical knowledge of the districts is, 

 appareml), as inexact as his manner of leading ; for he does 

 not seem aware that "the Stye," of which he speaks, is the 



name, not of a place, but of a rain-gaitge, in, as I said before, 

 the immediate neighbourhood of Stockley Bridge. 



J. K. L. 



Circumpolar Lands 



In the last number of Nature (Jan. 18), Mr. J. J. Murphy 

 asks, "Can any mathematical reason be a signed why the con- 

 traction of the earih should be least in the direction of the polar 

 direction ? This would account for the rising of the land at the 

 poles." 



In the Proceedings of the Literary and Philosophical Society 

 of Liverpool for Nov., 18^7, there is a piper on a probable 

 change in the earth's form, in which the rising of the land at the 

 poles is inferred as a necessary result of the cooling and contrac- 

 tion of the earth. 



The following is the substance, though not the exact words, of 

 a porion of the paper ; the precise words would not be in- 

 telligible without a diagram. 



If a spheroid of eqnilibrium, in motion about an axis, contract 

 uniformly in the direction uf lines perpendicular to its surface, a 

 new spheroid is produced, having a grea'er degree of eccentricity, 

 because if equal portions are taken off the two diameters, the 

 ratio of the equatorial to the polar diameter is increased. This 

 is equivalent to a heaping up of matter around the equator in 

 excess of what is due to the velocity of rotation, an increased 

 pressure on the interior, in that region, must be produced, and a 

 consequent transmission of pressure towards the poles. "A 

 change of form is then necessary to restore equilibrium. This 

 may not take place uniformly per graduin, for if there be a 

 resistance from a rigid external crust, tfie force must accumulate 

 until it exceeds the resistance, and thus frequent adjustinents/tv- 

 saltiim may ensue. It is probable, therefore, that the earth's 

 form is undergoing a slow progressive change." 



George Hamilton 



Queen's College, Liverpool, Jan. 21 



The Kiltorkan Fossils 



Mr. Batly's letter needs only a word or two from me. 



I must protest against my reference to an error made by 

 Mr. Baily being considered a "personal attack" upon him, or 

 an "accusation" against htm. Has Mr. Baily ever consulted 

 a syftematic work which did not contain corrections of the 

 real or supposed errors of former workers ? And did he con- 

 sider such corrections as " personal attacks " ? 



On two points Mr. Baily has misunderstood or misread the 

 plain statements of my letter : — I. I did not say that his draw- 

 ing in " Explanation of Sheets 187, he." was made on the spot 

 at Kiltorkan, but that it was a drawing of the fossil he had 

 nam d Sagenaria Veithcimia)ia ; 2. The qualifying phrase, 

 "coal measure," was used, as it often is, as the equivalent of 

 " carboniferous." How Mr. Ba ly could make it mean anythmg 

 else perplexes me ; seeing the Upper Carboniferous beds have 

 no connection with the question. To have used it in the limited 

 sense he suggests, and elaborately argues against, would have 

 been absurd. 



The remainder of Mr. Baily's letter is occupied with reference 

 to private letters as evidence in the case. That written by Mr. 

 B lily to Prof. Keer confirms the satement I made at the Geolo- 

 gical Society, and repeated in your pages ; but, in as far as it 

 declares that the specimens sent to Prof. Heer from Kiltotkan 

 were named .S". Bailyana, it differs from the statement made 

 by Prof Heer at ihe Geological Society, who, on ihi- evidence 

 of these fossils, included S. Vdthciiniana among the Kiltorkan 

 f jssils, and never mentioned S. Baiiyana ! 



The reference to the other private letters is equally unhappy ; 

 for Mr. Baily is quite wrong in supp 'sing my "accusation" was 

 made because I could not persuade him to join me in work. 

 My letter, if he will look at it again, bears a dale some 

 time after the "accusation" was made. And if at the 

 same time he will read his reply, he will find that the reason he 

 gave for declining to work with me is somewhat different from 

 those he records in your pages. But the fact is, the letters 

 hTve nothing whatever to do with my declaration, now more 

 than ever confirmed by Mr. Baily's letter, that his giving to 

 the Irish Le|iidoden'lroid plant the name of a carbonif rous 

 species misled Prof Heer. If Mr. Baily's letter indicates the 

 " facts" containrd in his paper, I can only concude that it was 

 the patriotism of your reporter that induced him to ctaracterise 

 them as "strong." W. CARRUXHliRS 



