P OP ULAR MIS CELL ANY. 



569 



across the water-shed leading over to the 

 Yellowstone Valley, and " they prove beyond 

 question that not only was that valley filled 

 up with ice, but that the glacier plowed 

 over the ridge one thousand feet above the 

 valley-bottom and passed into the country 

 lying to the westward." Professor Geikie 

 made an estimate of the thickness of the 

 ice, from the indications afforded by the 

 position of the highest erratics which he 

 observed on the slopes of Mount Washburn, 

 from which he concludes that it could not 

 have been less than sixteen hundred and 

 fifty, and was probably at least nineteen 

 hundred feet. It is clear to him, from all 

 the evidence, that the ice of the Yellowstone 

 Valley was more than that of a more local 

 or valley glacier. It was massive enough 

 to fill up the main valley and override the 

 surrounding hills, crossing minor water- 

 sheds and spreading into adjacent drainage 

 basins ; and he believes it may be eventu- 

 ally shown that the snow-fields of the Wind 

 River and Teton ranges were so extensive 

 that their ice-rivers streamed northward 

 across the buried water-shed, and poured 

 into the Yellowstone. An exploration of 

 the country lying in the Yellowstone Valley, 

 northward into the area of northern glacia- 

 tion within the British line, is desirable to 

 show whether there was any connection 

 between the glaciers of the Rocky Moun- 

 tains and the great northern ice-sheet, and 

 whether the latter, as it moved dawn the 

 valley of the Missouri, was swelled by the 

 accession of ice-streams from the moun- 

 tains. 



Structural Peculiarities of the Ed. 



Frank Buckland gives an interesting descrip- 

 tion of the curious yet simple apparatus by 

 means of which the eel is able to keep his 

 gills moist without taking in fresh water, 

 and thereby to live a long time out of water 

 and travel on land for a considerable dis- 

 tance. Close to the pectoral fin of the eel 

 is a slit which acts as a valve, connecting 

 with a large cavity inside of which are the 

 gills. This cavity the eel has the power of 

 filling with water, and of keeping within it a 

 supply which prevents the gill-fibers from 

 adhering together so as to stop respiration. 

 It is surrounded by a loose membrane, and 

 is filled and emptied by means of a curious 



bit of mechanism which is thus described : 

 " A framework of very delicate bones, each 

 bone connected with its neighbor by an clas- 

 tic membrane of the consistency of gold- 

 beater's-skin, forms a fan-shaped covering 

 over the gills ; its action is very like, if not 

 the same as, the action of an umbrella. 

 When the eel wishes to take in his water- 

 supply, he, as it were, opens his umbrella- 

 shaped framework and fills his reservoir; 

 when he wishes to expel the water, he, as it 

 were, closes his umbrella." When an eel is 

 taken out of the water he will soon expand 

 his reservoir, and swellings will appear on 

 either side of his head. He will shortly wish 

 to refill his reservoir, and, if given water, will 

 immediately take in a considerable quantity. 

 With this he is ready to take an overland 

 journey if he wishes to change his abode. 

 The eye of the eel is protected against the 

 mud, stones, etc., among which he lives by 

 what Mr. Buckland calls a wonderful specta- 

 cle or eye-glass, formed by the conversion 

 of the skin of the head where it passes over 

 the eye into a thin but strong transparent 

 membrane, which forms an admirable guard 

 against injury. 



Spilt Stones in the Desert. Those parts 

 of the desert of Sahara called the Hamadas 

 which are also among the most desolate 

 tracts of the region are strewed with sili- 

 cious pebbles which are all broken up, pre- 

 senting sharp edges, as if they had just 

 been split with a hammer. Sometimes frag- 

 ments of these pebbles could be found lying 

 together with their fractured sides facing 

 each other and fitting perfectly when brought 

 close together. The phenomenon has baffled 

 explanation for a long time. M. J. Brun 

 has recently communicated to the Scientific 

 Society of Geneva his conclusion that it is 

 the result of a curious combination of chem- 

 ical and mechanical actions. He found by 

 analysis that the sand of the desert was com- 

 posed of quartz, gypsum, and marl, with 

 traces of salt. The quartz-grains act under 

 the influence of the solar rays as burning- 

 lenses upon the gypsum, and render it an- 

 hydrous. The sand and fine anhydrous gyp- 

 sum-dust are driven about by the winds and 

 cover all the stones ; the dust penetrates the 

 little cracks in the stones, when it is wet by 

 the dews, and swells. With continuous ac- 



