Revieus — Charles Rahot — Length of Arctic Glaciers. 571 



Along the eastern margin of the Cretaceous area there is a porous 

 sandstone of great thickness, the ' Blythesdale Braystone,' and owing 

 to low dip the outcrop of this permeable stratum occupies a belt 

 from five to twenty-five miles wide ; but the Braystone finally 

 disappears beneath the argillaceous and calcareous upper members 

 of the series which forms the surface of the downs to the west. 

 Several rivers disappear while crossing the outcrop of the Braystone, 

 and the water must be carried in it beneath the clay-shales of 

 the downs. 



The outcrop of the Braystone is concealed over part of the area 

 by nearly horizontal tablelands of the 'Desert Sandstone,' an upper 

 member of the Cretaceous formation lying unconformably on the 

 lower divisions. It is, however, also of a permeable nature. The 

 author gives an estimate of the water which should penetrate the 

 Braystone, and suggests the probability that much of it finds an 

 outlet under the sea in the Great Australian Bight and the Gulf of 

 Carpentaria. 



The artesian water basins are, in fact, broken basins, and the 

 break gives rise to leakage either on land or beneath the sea. In 

 places, therefore, the water rises in a bore, but does not reach the 

 surface owing to the site of the bore being higher than the head of 

 pressure. This is termed ' sub-artesian water,' and the author gives 

 illustrations of both artesian and sub-artesian water in the district 

 in question. 



I^ IE "V I :h] "vt^ s. 



Les variations de longueur des Glaciers dans les Kegions 

 ARCTiQUES ET BOREALES. Par Charles Eabot. (Extrait des 

 Archives des sciences physiques et naturelles, 1899-1900.) 

 pp. 230. (Geneva and Bale : Georg & Co.) 

 rpmS is the latter part of a treatise of which the former was 

 X published in 1897. Since that date much additional informa- 

 tion has appeared, of which a summary is given, together with the 

 conclusions to which the author has been led. These are : — (1) Prior 

 to the eighteenth century the glaciers, as proved by docuiuentary 

 evidence in Norway and Iceland, and made highly probable also 

 in Jan Mayen and Spitzbergen, were much less extensive than they 

 are at the present day, and this minimum condition had lasted for 

 centuries. (2) During the eighteenth century, as well as in the 

 earlier years of the nineteenth, a very gi-eat extension {une crue 

 enorme) occurred, which was general throughout the Northern 

 Hetnisphere. In the course of this the glaciers invaded regions 

 which had been free from ice during historic times. Of this, in 

 Greenland, Jan Mayen, Iceland, Norway, and Alaska, in some cases 

 there is documentary proof; in others it is made highly probable 

 by less direct evidence. (3) The remainder of the nineteenth 

 century has been a period of uncertain movements. In some places 

 a considerable advance has been followed by a slight retreat ; in 

 others the latter set in after a pause at the maximum which had 

 been reached in the earlier years. At the present day the Greenland 



