May 28, 1874J 



NA TURE 



63 



drift, and direction of overturned edges of slialy slralo, and 

 proved tliat it did not flow down the valleys to the westward, 

 but passed across them and the ranges separating them, from the 

 north to the south. On the other side of the Irish Sea the Rev. 

 Mr. Close and others have shown that there also the ice did not 

 move down the valleys, but flowed along the coast southwards. 

 The ice-scratches still preser\'ed on the rocks prove that the 

 configuration of the land was nearly the same then as now, and 

 no explanation has ever been offered of tliis southerly movement 

 of the ice, excepting that it was prevented from flowing down 

 the natural slope of the land by the whole of the Irish Sea 

 having been at the time filled with ice up to a height of about 

 2,000 ft. above the present sea-level. The Isle of Man, that lay 

 in the path of this great ice-stream, is glaciated from top to 

 bottom, and it must have been completely buried in ice. It is to 

 the action of this great agent that I ascribe the pushing up of 

 sand and shells over south Lancashire, Cheshire, and North 

 Wales on one side, and Wexford and around Dublin on the 

 other, of the Irish Sea, where the course of the ice southward 

 was obstructed by the narrowing of the channel. 



So far from the movement of this great mass of ice being 

 deflected or warded off by local glaciers, we have seen that in 

 north Lancashire it was not affected by them ; and long ago 

 Vrof. Ramsay proved that the glaciation of Anglesea and the 

 west of Caernarvonshire had not radiated from the higli land, 

 but that the ice had come from the north and brought with it 

 numerous boulders from the mountains of Cumberland. 



As to the possibility of ice, pushed forw.ard by higher accumu- 

 l.ations behind it, thrusting before it loose sand and shells up to 

 higher levels, I may remark that there are many proofs that it 

 possesses this power. In the Isle of Man blocks of granite have 

 been pushed up 600 feet above the level of their source. Mr. 

 Tiddemann has also shown that as the ice moved across the val- 

 leys down one side and up the other, it thrust over the edges of 

 the strata. On the other side of the great English watershed, 

 Mr. Dakyns has shown that the ice when ascending the slope of 

 a valley opposed to its course swept before it all the drift lying 

 on the surface, pushing it over to the other side of the range. 



Mr. Bonney would be more likely to damage my theory if, 

 instead of protesting against it, he could explain some of the 

 many dilTiculties that beset that of submergence. Where was 

 the shore of that mythical sea under which England nearly to 

 the Thames is supposed to have been submerged? How is it 

 that not a single undisturbed bed of glacial shells has been 

 found, that nearly all are broken to pieces, that many fragments 

 of Cyprina exhibit glacial scratchings, and that not a single in- 

 stance has been recorded of the two valves of a lamellibranch 

 having been found together ? Was there no friendly cliff or 

 cavern able to preserve a single shell from the ruthless second 

 advance of the ice? Mr. James Geikie finds the fragile bones of 

 water-rats and frogs in his "inter-glacial beds," and uninjured 

 laud and tresh-water shells occur in abundance ; but not one 

 marine shell has been found in the uplands that does not show 

 proof of having been transported, by being broken, worn, or 

 scratched. 



Since my first letter was sent to N.\TURE, Prof, Ramsay has 

 drawn my attention to Mr. Croll's theory, that the glacial shells 

 of Holderness had been pushed up by ice over the land out of 

 the German Ocean. From other papers of the same geologist, 

 I gather that he does not dispute the submergence of much of 

 England and Scotland during part of the glacial period, and has 

 indeed proposed a theory to account for it. So far as I know I 

 stand alone at present in the opinion that neither during nor 

 since the glacial epoch has there been any submergence of a 

 great part of the British Isles beneath the waters of the ocean, 

 nor can I expect that a theory so contrary to what has been 

 taught for many years by English geologists will obtain a ready 

 acceptance. Thomas Belt 



Ealing, May 22 



Uncompensated Chronometers 

 With reference to the employment of an uncompensated 

 chronometer to indicate the mean temperature of an accompany- 

 ing compensated chronometer during a long journey, with a view 

 to the application of the proper correction for temperature, Prof. 

 G. Forbes remarks (Nature, vol. x. p. 50) : — 



"This method is quite new, and has not been tested by any 

 nations except the Russians." 



Permit me to direct attention to the following passage in the 

 " Report on the Coast Survey," which I extract from p. 66 of 



the Proceedings of the American Association for the Advance- 

 ment of Science, Springfield meeting, August 1S59. The 

 " Cambridge " referred to is Cambridge, Massachusetts. 



" The difference of longitude between Cambridge and Liver- 

 pool has also been determined by means of large numbers of 

 chronometers carried repeatedly between the two stations on the 

 Cunard steamships. These chronometric expeditions, in the 

 words of Mr. W. C. Bond, director of the Harvard Observatory, 

 ' for the magnitude and completeness of their equipments, have 

 not been equalled by any of the similar undertakings of European 

 Governments. Even the E.xprdition clironoinctiiijue of Struve 

 was on a scale much less extensive.' The voyages were con- 

 tinued through a number of successive years. The first great 

 special expedition took place in '849, and the most recent in 

 1S55. In the latter the effect of temperature on the rate of the 

 chronometers formed a subject of special investigation. For 

 each instrument the effect of temperature on its rate was ascer- 

 tained by experiment, and the average temperature during each 

 trip was kept account of by means of a thermometric chrono- 

 meter, constructed like the others, but with individual balance, 

 so that its daily rate was affected by six seconds for a change in 

 temperature of l° Fahr. Fifty-two chronometers were employed 

 in this expedition, and were transported six times between Cam- 

 bridge and Liverpool." 



The " Greenwich Observations " for many years past (fifteen at 

 least) contain a record of the indications of a " chronometrical 

 thermometer " accompanying the chronometers on trial for pur- 

 chase by the Admiralty; and on p. 2 of " Rates of Chrono- 

 meters" in the volume of Observations for 1S71 are these 

 words : — 



" The chronometrical thermometer differs from an ordinary 

 chronometer only in the construction of the balance, the posi- 

 tions of the metals forming the compensating rims being reversed. 

 By this arrangement the eflfect of temperature is much mag- 

 nified." J. D. Everett 



Malone Road, Belfast, May 22 



Photographic Irradiation 



In Nature, vol. x. p. 29, the article on the coming Tr.insit of 

 Venus makes mention of photographic irradiation as having " been 

 found by Lord Lindsay and Mr. A. C. Ranyard to be mainly 

 due to the rellection of light from the back of the glass plate. 

 It can be almo t entirely avoided," Mr. Forbes goes on to say, 

 " by wetting the back of the plate and placing black paper 

 against it." This subject has been investigated, explained, and 

 the above remedy suggested years ago . hy practical photo- 

 graphers. In 1867 I used the plates of the Liverpool Dry 

 Plate Company, then sent out with the backs painted red to pre- 

 vent irradiation. 



But even this is not a complete preventive. . Colouring the 

 film, as suggested by Mr. Carey Lea of Pliiladelphia and Henry 

 Cooper, a well-known English amateur, is a much more effectual 

 means, though at a loss of sensitiveness ; but th\e most complete 

 (where the dry emulsion process is available) is to allow the col- 

 lodion to be acted on by a large excess of nitrate of silver for a 

 considerable time and then to convert this into bromide of silver 

 by addition of airmonium bromide. The result is that the film 

 has a dull opaque character like unglazed porcelain, and not only 

 stops the light more completely than an ordinary collodion fihn, 

 but remedies another cause of irradiation — the molecular re- 

 flection in the film itself. 



Two years ago I tested plates prepared in this way on the 

 most difficult subjects (not astronomical) and found the halation 

 much less than by any other means except a deep red tint in the 

 film. W. J. Stillman 



Hay Fever 



Referring to the recent article in (Nature, vol. x.p. 26) upon 

 hay fever, I can give my own experience as having suffered from 

 the complaint for some years past, mainly in the months of May 

 and June . My most severe attacks have been in the house in early 

 morning. I am, however, near hay-fields, and a tramp, by way 

 of experiment, through one of these has more than once satis- 

 fied me of the efficacy of the hay pollen in vastly increasing the 

 troublesome symptoms. 



The treatment I have u«ed to myself has consisted of rather 

 strong doses of quinine taken internally, and externally a piece 

 of linen rag dipped in strong camphorated spirit and placed upon 

 the nose and also partly over the nostrils. 



