February 9, 191 1] 



NATURE 



475 



the mechanism by which it might be accomplished, is 

 shown by "is invention of the " provisional hypothesis " 

 of jjangent^is, has been justly pointed out by Sir William 

 Thiselton-Dyer. In introducing this hypothesis Darwin 

 ivrote : — 



" A multitude of newly acquired characters, whether 

 injurious or beneficial, whether of the lowest or highest 

 vital importance, are often faithfully transmitted . . . and 

 we may on the whole conclude that inheritance is the 

 rule, and non-inheritance the anomaly " (" Variation of 

 Plants and Animals," popular edition, p. 454) 



No mistake can be greater, as it appears to me, than 

 one prevalent at the present day — namely, that by the 

 newer developments of evolutionary theory in Weis- 

 mannism, Mendelism, &c., Darwin's results are in any 

 way superseded. On the contrary, I firmly believe that 

 had Charles Darwin lived, no one would have more gladly 

 welcomed these new developments than would he ; for he 

 would have rejoiced to follow the investigations of the 

 particular methods by which variations are transmitted, 

 the possible limits of individual variation, and the laws 

 Ti-hich govern their appearance. 



Kew, February i. John W. Judd. 



Glacial Erosion. 



The reviewer of " Geographical Essays," by Prof. 

 \V. M. Davis, writes in Nature of January 19 : — " Prof. 

 Bonney's presidential address to the British Association 

 has brought the controversy on glacial erosion to a head. 

 It may be hoped that the authoritative and masterly state- 

 ments on both sides will lead to an agreement as to the 

 main facts, but no settlement can be expected until the 

 arguments of those who limit the efficacy of glaciers as 

 eroding agents have been directly answered." 



I do not think that those who, like myself, hold that 

 glaciers are powerful eroding agents would shrink for a 

 moment from directly answering their opponents' 

 ■criticisms. The most direct answer is that the deposits 

 formed by glaciers are a direct measure of glacial erosion. 

 I distrust ail theoretical opinions based upon the study of 

 ice as a " rock.," In the early days of geological science 

 it was difficult to convince the many that the "purling 

 brook " and the " babbling river " had frequently ex- 

 cavated the deep valleys and gorges through which they 

 run. 



Do the opponents of glacial erosion really contend that 

 the enormous deposits of boulder clay which cover such 

 extensive portions of England, Scotland, and Ireland are 

 not the results of glacial erosion? I say boulder clay 

 advisedly ; tor there are immense deposits of laminated 

 clay with or without boulders, sands, and gravels, which 

 some may argue have no connection with glaciation. 

 Here, however, I should again differ, for many years of 

 careful study in the field have convinced me that nearly 

 all these superficial or "drift" deposits are the result of 

 glacial erosion. 



Taking the " glacial " deposits themselves as a measure 

 of glacial erosion, and concluding that we must look for 

 marked effects in the areas from which the material was 

 eroded, what do we find? We find surface lowland 

 features, valley gradients, valley forms, and entire valleys 

 and gorges, which are not such as are produced by the 

 erosive action of water, rain, and frost. 



The opponents of glacial erosion have been too much 

 guided by glacial action, as now seen in such mountainous 

 areas as Switzerland. The puny glaciers now found there 

 cannot be compared, so far as the effects they produce 

 are concerned, with the great confluent glaciers which 

 once occupied the valleys. 



It is a pity that in this country the conviction which 

 so many hold concerning glacial erosion and climatal 

 changes should have resulted in the stagnation of glacial 

 geology as a science, for it cannot iS denied that if 

 glaciers have done very little as agents of change, there 

 must be very little to study. 



Glacialists of the active school cannot but feel grateful 

 to such workers as Prof. James Geikie, Prof. W. M. 

 Davies, Prof. R. S. Tarr and others, for keeping the lamp 

 burning- R. M. Deeley. 



Inglewood. Longcroft Avenue, Harpenden, 

 January 18. 



Hardly anyone disputes that the passage of ice over 

 the British Uplands swept away all the loose rock materials 

 and redeposited them in the Lowlands as glacial drifts. 

 The controversy is not as to the removal of the loose 

 debris, but of the excavation of basins in fresh hard rocks. 

 •As Mr. Deeley states, the opponents of glacial erosion 

 have written extensively ; but certain serious difficulties 

 that have been advanced by Prof. Bonney, Prof. Garwood, 

 and others, do not seem to me to have been directly 

 answered. I share Mr. Deeley *s gratitude to the three 

 geologists whom he names for their important contribu- 

 tions to glacial geology. J. W. G. 



An Unconscious Forecast by Joule. 



The following remarks by Joule in his paper on the 

 changes in temperature produced by the rarefaction and 

 condensation of air (Phil. Mag., May, 1845J are worthy 

 of notice : — 



" The beautiful idea of Davy, that the heat of elastic 

 fluids depends partly upon a motion of particles round 

 their a.xes, has not, I think, hitherto received the atten- 

 tion it deserves. I believe that most phenomena may be 

 explained by adapting it to the great electrochemical dis- 

 covery of Faraday by which we know that each atomic 

 element is associated with the same absolute quantity of 

 electricity. Let us suppose that these atmospheres of 

 electricity, endowed to a certain extent with the ordinary 

 properties of matter, revolve with great velocity round 

 their respective atoms. ..." 



" The phenomena described in this paper, as well as 

 most of the facts of thermochemistry, agree with this 

 theory ; and in order to apply it to radiation we have only 

 to admit that the revolving atmospheres of electricity 

 possess, in a greater or less degree, according to circum- 

 stances, the power of exciting isochronal undulations in 

 the ether which is supposed to pervade space." 



In the idea of the " atmosphere of electricity " revolving 

 round the atom, we have the substance of J. J. Thomson's 

 corpuscular theory, while the electromagnetic mass of the 

 revolving " atmospheres of electricity " would certainly 

 cause them to be " endowed to a certain extent with the 

 ordinary properties of matter." -Again, the last phrase of 

 the extract is simply the modern idea of electromagnetic 

 waves in the aether. 



The premature birth, in this short quotation, of three 

 of the most startling advances of modern physics is not 

 a little remarkable. B. A. Keen. 



University- College, London, January 25. 



The Sailingr-Flieht cf Birds. 



In a letter to Nati.re in February, 1876, I suggested 

 that the sailing-flight of birds and the flight of flying-fishes 

 could be explained as tobogganing under almost perfect 

 conditions, and in 1889 the late Duke of Argyll accepted 

 this, in a letter to the Spectator, as a correct and 

 sufficient explanation. My old friend the late Prof. H. N. 

 Moseley, a member of the Challenger staff, held the view 

 that a quivering, imperceptible to the eye, of the wings 

 and fins was the true explanation. I do not know which 

 explanation has been generally accepted, but I would 

 suggest that a kinematographic picture of the flving-fi«h 

 ought to settle the question finally, if it is not alreadv 

 settled. 



I said in my letter : — " By means of a suitable 

 mechanism for changing the inclination of the wing-planes 

 every few seconds the sailing-flight of the albatross, I 

 believe, might be simulated without much difficultv." Has 

 not the aeroplane done this? R. Abbay. 



Earl Soham Rectorv, February i. 



NO. 2154, VOL. 85] 



A Morning Meteor. 



.A METEOR equal in brightness to the Pole Star, and of 

 much the same colour, was seen by me to fall from the 

 southern sky at 6.25 on the morning of Fridav, February 3. 

 Its path was one of ten degrees, extended along a line 

 midway between a Coronae Borealis and the planet Jupiter, 

 which at that time was shining lustrouslv some thirty-four 

 degrees south, and slightly east, of .Arcturus. The meteor 

 left a steel-blue train which remained visible for six 

 seconds. Joseph H. Elgie. 



72 Grange .Avenue, Leeds. 



