January 



898] 



NATURE 



245 



dealing with the fundamental principles of physical 

 science, and the second with physical geography as it is 

 generally understood. The complete syllabus thus pro- 

 vides the outlines of an elementary course of general 

 science. Mr. Thornton's book has been written upon the 

 lines of the first part of the syllabus, and therefore it is 

 limited to brief treatment of the elementary facts and 

 principles of physics and chemistry. A large number of 

 experiments are included, some of them good. The 

 illustrations are also numerous, and some of them are 

 original. 



The Wealth and Progress of New South Wa/es, 1895-96- 

 By T. A. Coghlan. Vol. i. Ninth issue. Pp. 491. 

 (Sydney : Government Printer, 1897.) 

 The difficulty in preparing a volume of this kind is to 

 limit the information concerning the details of local 

 affairs, and yet make them useful both locally and to the 

 outside world interested in the features and progress of 

 our colonial possessions. Mr. Coghlan, the Government 

 Statistician of New South Wales, seems to have success- 

 fully adjusted the balance of the two interests, with the 

 result that his volume appeals to all who wish to have 

 accurate information concerning the active life of the 

 Colony. Moreover, there are chapters on the history of 

 the Colony, the climate, geological structure, physical 

 configuration, fauna, flora, forestry and fisheries, and 

 mines and minerals. The volume will be very service- 

 able for reference. 



LETTERS _ TO THE EDITOR 



[The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undei-take 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of NATURE. 

 No notice is taken of anonymous communicationsJ\ 



The Glacial Period and the Irish Fauna. 



It has been shown by the work of many observers, in Scot- 

 land, Ireland, north-western England and the Isle of Man that 

 during the Glacial Period the basin of the Irish Sea must have 

 been filled with an ice-sheet. It is not probable, therefore, that 

 the interesting speculations of Dr. Scharf on the origin of the 

 Irish fauna (Nature, October 28, 1897), in so far as they are 

 based upon assumptions as to ihe glacial conditions of the Irish 

 Sea, will meet with much acceptance among geologists. 



There is one possible mode of migration for land-animals in 

 formerly glaciated regions which I think has been too frequently 

 ignored by students of the subject. I refer to the probability 

 that the ice-sheet itself may have furnished a practicable route 

 across narrow seas. In Prof. I. C. Russell's luminous description 

 of the Malaspina Glacier of Alaska, we read that "a broad 

 game-trail which had evidently long been used by bears, wolves, 

 foxes and mountain-goats," skirting the Chaix Hills, "con- 

 tinued across the glacier 6 or 8 miles north-eastward to the 

 Samovar Hills." Again, Dr. Scharf himself incidentally men- 

 tions that in Northern Europe "it is a well-known fact that 

 reindeer are in the habit of travelling considerable distances 

 on ice." 



During my recent survey of the Isle of Man I have found 

 abundant evidence to show that during the maximum glaciation 

 an extraneous ice-sheet swept across the highest summit (2034 

 feet), and also that during the closing stages of the Glacial 

 Period this ice-sheet melted away more rapidly in the vicinity 

 of the island than in the surrounding obliterated sea-basin. 

 Under such conditions the island formed a nunatak accessible 

 for any animal which could cross ihe ice. And I think that 

 the general circumstances attending the close of the Glacial 

 Period indicate that most of the land surrounding the enclosed 

 sea-basins in our latitudes might be in a condition to sup- 

 port animal life before the decaying ice-lobes had disappeared 

 from these hollows. During the earlier stages of the Glacial 

 Period it is clear that the climate was such as to favour 

 the accumulation of glaciers even at sea- level, and this con- 

 dition persisted until ice-sheets of great thickness had covered 

 the lowlands. This growth at length ceased ; perhaps, as I have 

 elsewhere suggested, in the east sooner than in the west, because 



NO. 1472, VOL. 57] 



of the greater amount of snowfall along the western periphery 

 of the sheet. 



In the northern part of the Irish Sea basin there existed a 

 high plateau of ice, its surface probably not far, if at all, short 

 of 3000 feet above present sea-level. An amelioration of climate 

 set in, and progressed until, say, no permanent snow was possible 

 at any altitude under 1000 feet. But the ice-sheet was already 

 in possession, and by reason of its elevation w<juld remain, 

 throughout the greater part of its area, uninfluenced by this extent 

 of change, or it might even still continue to grow where there 

 was sufficient precipitation. In an ice-choked basin hemmed 

 in by hills as is the Irish Sea, the discharge by flow alone was 

 scarcely likely to keep pace with the surface accumulation. 



Not until the climate became such that melting was in 

 progress over the whole plateau would there be much general 

 lowering of its surface. Under such conditions, as the elevation 

 of the ice-sheet was equal to, or greater than, the uplands upon 

 which it abutted, the snowfall could no longer remain perman- 

 ently, even on the hilly ground. Hence, as the land emerged 

 from its icy covering, it would remain bare, and ready to support 

 vegetation. As on the Malaspina Glacier, even the ice itself, 

 where covered with morainic debris, might become verdure-clad. 



The melting influence of rain falling upon the ice-sheet 

 would be distributed equally over the recipient surface, for its 

 superfluous heat would be at once absorbed. But whatever rain 

 fell upon the emerging land could gather and flow in compara- 

 tively warm streams, capable of exerting a considerable differ- 

 ential effect where they impinged upon the margin of the ice. 

 There would thus be a general tendency for the melting mass to 

 shrink down more quickly in the vicinity of land ; and this 

 effect would be accelerated as the lower levels were uncovered. 



These are the conditions disclosed by the field evidence in the 

 Isle of Man, and that Ufe existed under such conditions is 

 proved by the presence, in one of the gravel-terraces of this 

 period, of the arctic fresh-water crustacean Lepidurus [Aptts) 

 glacialis, which lives now in icy pools near glaciers in Norway 

 and Spitsbergen, along with an arctic willow, Salix herbacea, 

 and a few other plants of wider range. 



The Irish Elk reached the Isle of Man about this time, and I 

 think it probable that it crossed from the mainland on the 

 waning ice-sheet. The evidence is altogether unsatisfactory for 

 a Post-Glacial land-connection, as Mr. P. F. Kendall has shown. 



The distance between the nearest points of Ireland and Scot- 

 land is about the same as between the nearest points of the Isle 

 of Man and Scotland, and I see no reason why certain elements 

 of the Post-Glacial fauna of Ireland should not have been 

 similarly introduced by the ice-bridge. At any rate, in view of 

 the above-quoted data furnished by the Alaskan Glaciers, this 

 appears to me to be a legitimate supposition, and one which is 

 in keeping with the general trend of the geological evidence. 



G. W. Lampi.ugh. 



The Variability of Mira Ceti. 



The notes in Nature, December 2 and 9, are very welcome, 

 as they show more interest in o Ceti than in late years, and 

 especially as from present information there have been but few 

 observations from this side on the recent appearance. It seems 

 that I have seen, so far, more of the star than any one else. 



The maximum of Mira, following previous ephemerides, was 

 due October i . But The Companion and Chandler have added 

 a correction of about forty days, and given the date as November 

 9. This phase appears to have occurred this season November 

 30, which is sixty days late. But it is not at all improbable that 

 another maximum may be observed, although the star seems now 

 to have broken away definitely. It was a step or so brighter 

 than a star (3 '99 H.P.) last night, and is unchanged to-night 

 except in colour. Its reddish cast to-night, judging from some 

 past experiences, indicates a change in light, and another rise 

 may occur. 



The magnitude November 30 was 3*2, Gamma Ceti being 

 3 '59 Harvard measurement. 



It is remarkable that while there is agreement as to the light- 

 curve of Mira for three years, the dates of maximum are as much 

 as five weeks apart. • But there still remains some doubt as to 

 the fluctuations in 1894-95 ; and did not Mr. H. M. Parkhurst 

 confirm the present writer's observations of that apparition, they 

 would have been thrown out of court. And some doubt would 

 attach to Mr. Parkhurst's did not an observer at Moscow, men- 

 tioned in Nature, confirm both of us. David Flanery. 



Memphis, Tenn., U.S.A., December 24, 1897. 



