88 Revieivs — Cambridge County Geographies. 



gravels, and there is a separate topographic map to illustrate the 

 Yentna mining district. The gold has been derived from aurifei'ous 

 quartz-veins in the Birch Creek schists and other of the older 

 metaraorphie rocks. The audesitic lavas of Jurassic age also contain 

 a little gold. 



Some account is given of the past and present glaciation of the 

 region, and Mr. Brooks remarks that " A rough estimate indicates 

 that less than 1 per cent of the area formerly covered by ice still 

 remains buried under glaciers and perpetual snow. The present 

 glaciers appear to be rapidly retreating and represent the lingering 

 remnants of the larger Pleistocene ice-sheets". He further observes 

 that "The subject of ground ice is worthy of mention. It ap|)ears 

 that on the south side of the Alaska Range the ground thaws out 

 to bed rock every season. North of the range grouiui ice is nearly 

 everywhere present under 1 to 2 feet of soil and humous matter. 

 This layer remains frozen throughout the year. Usually where the 

 alluvial material is undrained the permanent frost extends to bed rock, 

 in one place 3 1 8 feet of fi'ost having been measured. Locally, however, 

 where loose gravels are encountered, the material is not frozen ". 



Hot springs are noted on the holders of the Tanana liiver, a tributary 

 of the Yukon, in the Baker Gold Placer District. 



It only remains to add that the work is illustrated by eighteen 

 excellent pictorial views and maps, geologic and topographic, and by 

 thirty text-figures. 



IV. — Cambridge County Geographies. 



Ij'^OUIl additional volumes have been received of the Cambridge 

 _ County Geographies. They comprise East London, by Mr. G. F. 

 Bosworth ; Monmouthshire, by Mr. Herbert A. Evans ; the Isle of 

 Man, by the Rev. John Quine ; and Carnarvonshire, by Professor 

 J. E. Lloyd. 



East Loudon is taken to include the boroughs of Islington, Stoke 

 Newington, and Hackney on the nurtli, and those of Caniberwell, 

 Lewisham, and Woolwich on the south. The volume is an interesting 

 one, containing accounts of the parks, commons, and open spaces, of 

 the rivers past and present, water-supply, geology (in brief), rainfall, 

 industries, and many other matters. The illustrations are good, 

 and include a view in Epping Forest, a fair on the frozen Thames in 

 1814, bridges old and new, Canonbury Tower, Staple Inn, Holborn, 

 London Wall, and many others. Although Boulder-clay is mentioned 

 in the text it is not present in the area; on the other hand, Blackheath 

 Beds sliould have been noted, with Woolwich and Tlianet Beds, on 

 the geological map This work has the advantage of an index, which 

 is not the case with the three other volumes now before us. In these 

 space is taken up unnecessarily by a full instead of a local table of 

 geological formations, while in the volumes on Monmouthshire and 

 the Isle of Man there are neiirly three pages (alike in both) dealing 

 with an explanation of geology. Mr. J G. Wood has contributed 

 local geological notes, all too brief, on Monmoutlishire. He remarks 

 that the Severn Sea lies in a great "trough fault", but this is not 



