December 7, 1893] 



NATURE 



123 



otherwise." Indeed, from the tone of his letter he would ap- 

 pear to be defending modern science against the attacks of cer- 

 tain unscientific persons who hold extreme views on glacial 

 questions. As one who has taken a great interest in this subject 

 for a number of years, I trust that I may be allowed to add a 

 few words to the discussion. 



We are required by Sir Henry Howorth to establish two 

 postulates. "(i) That ice can convey thrust for more than a 

 moderate distance. (2) That glaciers, such as we can examine 

 and report upon, are anywhere at this moment doing the ex- 

 cavating work ..." Dr. Wallace postulates. 



In reply to the first, we have the undoubted fact that 

 in hundreds and thousands of instances striated rock sur- 

 faces do occur hundreds of miles from existing glaciers. On 

 this point he remarks : " If glaciers travelled further in 

 former days, it was doubtless because glaciers were larger 

 in former days, because they descended longer slopes, and 

 had larger gathering grounds ; that is to say, because the 

 country where they grew was more elevated." So the glacial 

 period resulted from elevation, and all glaciated regions con- 

 veniently rose together to produce it, and as conveniently sank 

 down again. I was quite unaware that this was the accepted 

 view. We have no proof whatever that the striated slopes 

 down which the old glaciers moved were steeper in glacial 

 times than they are now. Indeed, the proof is all the other 

 way, and we may consider it as proved that at long distances 

 from their sources, and on comparatively level plains, glaciers 

 have moved, and have polished, ground, scratched and grooved 

 the rocks over which they passed. The only point about which 

 there may be legitimate discussion concerns the possible extent 

 of the abrasion. 



In his mechanics Sir Henry Howorth is, I am afraid, rather 

 unsound. There are really two factors upon which the possi- 

 bility of motion in a viscous body depends. One is, of course, 

 the slope of the surface over which it passes, and the other is 

 the slope of the upper surface of the viscous body. Fracture 

 and regelation have little to do with the question, for fracture 

 only occurs near the surface, and fracture must not be con- 

 founded with shear. Sir Henry Howorth makes one statement 

 which seems to account for the conclusions he has come to. 

 It is " a viscous body, unless the viscosity approaches that of a 

 liquid, cannot move by mere hydrostatic pressure." In fact he as- 

 sumes, without adducing a particle of evidence in support of the 

 assumption, that there is an inferior limit to the stress required 

 to deform glacier ice. I always regarded viscosity as something 

 which retarded motion, but did not in any way interfere with 

 the ultimate result. I have personally made mechanical tests 

 of ice, and also of many thousands of samples of steel, iron, 

 copper, brass, tin, &c. All these substances yield elastically 

 and permanently under stress, some of them under very small 

 stresses, but ice is the only one of them that yields continu- 

 ously from the moment the stress is applied until it is again 

 removed. 



It is not, properly speaking, pressure from behind that forces 

 the ice forward. Ice being viscous, every individual particle 

 moves in the direction of least resistance at a rate depending 

 upon the stress and the viscosity. Sir Henry Howorth may 

 term this "Geology in Nubibus," and call it unmechanical ; 

 but I would point out to him that I regard the question from 

 the point of view of a mechanical engineer, which I am afraid 

 he does not. 



During the past summer I had the pleasure of seeing some 

 of the Norway glaciers, and also of crossing the Folgefond 

 snow field. It was interesting to note that although the streams 

 coming from the hills and uplands free from ice were quite clear, 

 those escaping from the glaciers were charged with sediment. 

 In this connection I would call attention to a calculation made 

 by Prof. G. F. Wright, giving the rate of erosion of its bed by 

 the Muir Glacier. From the volume and turbidity of the 

 water he makes the figure one-third of an inch per annum over 

 the whole of the 1200 square miles of area occupied by the 

 glacier. In fact, erosion goes on much more rapidly when the 

 rocks are covered by moving ice than when they are not. 

 Although we may feel absolutely certain, both by fact and 

 reason, that the erosion beneath glaciers when they are moving 

 with relative rapidity is very great, and be as sure as we reason- 

 ably can be of most things that such erosion must result in the 

 formation of lake basins, I am afraid that we shall be un- 

 able to satisfy Sir Henry Howorth on the point. We cannot 

 remove a glacier, and if there should prove to be a rock basin 



NO. [258, VOL 49] 



below measure of its depth, then replace the ice, and measure 

 again, say, in a thousand years. This is the kind of proof the 

 second postulate seems to demand. R. M. Deeley. 



The " Zoological Record." 



In reference to the letter of Messrs. Pocock and Bather, on 

 the subject of the Zoological Record, in Nature of No- 

 vember 16, I desire to state that the council of this Society (to 

 which the Zoological Record at present belongs) quite agree 

 with the above-named gentlemen in their wish to render 

 the Zoological Record more complete by combining palao- 

 zoology with it. With this view the council some time since 

 addressed the Geological Society, and suggested what in their 

 opinion would be an equitable arrangement for carrying out the 

 plan. This arrangement, however, as will be seen by the copy 

 of the correspondence enclosed herewith, was rejected by the 

 council of the Geological Society. It remains, therefore, for 

 Mr. Bather and such members of the Geological Society as may 

 share his sentiments, to do their best to induce the council of 

 the Geological Society to alter their views upon this question. 



I have good authority for stating that the editor of the 

 Zoological Record is not really of a different opinion to Messrs. 

 Bather and Pocock on this subject, as would seem to be 

 interred in their letter. I believe that he only suggested 

 that the paleontologists should start a record for themselves 

 because of the refusal of the Geological Society to co-operate 

 with us in our work. P. L. Sclater. 



Zoological Society of London, 

 3, Hanover Square, London, W. 



(Copy.) 

 To the Secretary, the Geological Society, Burlington House, W. 



Dear Sir, — I am instructed by the council of this Society to 

 apply to the council of the Geological Society under the follow- 

 ing circumstances : 



When the Zoological Record (which is now carried on by this 

 Society) was established twenty-eight years ago, it was not con- 

 sidered that palceozoology came within its scope, and the re- 

 corders were instructed to notice only such palasontological 

 works as appeared to be "of interest to the student of living 

 forms " in their records. This part of the subject has, however, 

 received a continually increasing amount of attention from the 

 recorders, and the council of this Society, being desirous that 

 paloeozoology should in future be treated of in the Record as 

 completely as recent zoology, asks the assistance of the Geolo- 

 gical Society in carrying out this object. 



The Zoological Society bears at present a loss of about ;^3SO 

 per annum, arising from the publication of the Zoological 

 Record, and, as the inclusion of palseozoology in an exhaustive 

 manner would materially increase the work of the recorders, 

 and necessitate an addition to their remuneration (which is even 

 at present too small), the council of this Society asks the 

 council of the Geological Society to make a grant of ;i^ioo 

 annually towards the expenditure thus incurred. 



It is thought by some members of the Council that the Zoo- 

 logical Society, bearing, as it does at present, the whole loss 

 arising from the publication of the Record, should not increase 

 its expenditure thereon, and the sum mentioned above, ;^ioo, 

 would, it is estimated, be sufficient to relieve this society from the 

 additional expense that the inclusion of palaeozoology, in its 

 record of zoological literature, would involve. In return for this 

 assistance, the council of this Society will make every effort to 

 treat the subject of palaeozoology exhaustively, and will add to 

 each A'6'C(7r(f a reference to palaeozoological memoirs stratigraphi- 

 cally arranged, besides dealing with those memoirs in detailed 

 analysis in the systematic records. 



In order that the interests of palseozoology may be more 

 carefully attended to, the council of this Society will undertake 

 to place a nominee of the Geological Society upon the com- 

 mittee of their body appointed every year to supervise the 

 publication of the Zoological Record. 



Should these proposals meet with acceptance from the Geo- 

 logical Society, the council will further undertake to place one 

 hundred copies of the Zoological Record at the disposal of the 

 Geological Society, and, if it be wished, will alter the title of 

 the Record to The Record of Zoological and PalcEozoological 

 Literature, from The Record of Zoological Literature. 



