520 Reviews — Jukes-Browne — Post- Tertiary Cambridgeshire. 



which certain mineral silicates, such as serpentines, hornblende, and 

 micas, are occasionally met with. It is in those aluminiferous rocks 

 which are without lime and magnesia, that are found the essential 

 and characteristic differences, and these depend upon a progressive 

 diminution in the proportion of the alkalies to the alumina, as we 

 pass from the older to the newer geognostical groups" (p. 210). 



The above classification is different from the opinions held by the 

 author previous to 1871, as he maintained that the crystalline rocks 

 of the Green Mountain and White Mountain series were altered 

 Palaeozoic sediments, but which he now considers to be of Pre- 

 Cambrian age. 



Some of Dr. Hunt's views given in the report are not in ac- 

 cordance with those of Pennsylvania geologists of the first or second 

 surveys, and although the State Geologist (J. P. Lesley) feels " it is 

 somewhat premature to dogmatise about the Taconic system ; as it 

 is impossible yet for any competent judge to express a positive 

 opinion respecting such terms as Montalban, Norian, etc., in Penn- 

 sylvania," yet he fairly acknowledges " that a debt of gratitude is 

 due to Dr. Hunt for this historical monograph, which will supply a 

 deeply felt deficiency in the literature of our science." J. M. 



III. — The Post-Tertiary Deposits of Cambridgeshire. By A. J. 

 Jukes-Browne. 8vo. pp. 85. (Cambridge, Deighton, Bell & 

 Co., 1878.) Price 2s. 6d. 



IN 1876 the Sedgwick Prize was awarded to Mr. Jukes-Browne for 

 an essay on "The Post-Tertiary Deposits of Cambridgeshire 

 and their relations to deposits of the same period in the rest of East 

 Anglia." This with some few additions is here reproduced, and is 

 so neat in form and moderate in price that our Geological Survey 

 authorities might well take a lesson from it. 



Commencing with some historical notices on the study of drifts in 

 general, the author proceeds to review the various works dealing 

 with the tract he describes — from the time of the Eev. Professor 

 Hailstone in 1816 to the date of his own publication. After a brief 

 account of the physical features of Cambridgeshire, he turns at once 

 to the description of the Glacial Beds. These include the Chalky 

 Boulder-clay, usually classed as Upper Glacial, and certain gravels. 

 Mr. Jukes-Browne considers that the Boulder-clay was accumulated 

 during the period of most intense glacial cold, and he would not 

 exclude other beds from the glacial series simply because they 

 happen to lie above this particular clay. 



No deposits of Lower or Middle Glacial age are recognized by 

 him in the area, for although here and there certain sands and loams 

 are interposed between beds of Boulder-clay, he regards this feature 

 as probably the result of contemporaneous current action. Brief 

 mention is made of the great boulder of Gault and Chalk seen in the 

 celebrated pit at Roslyn Hole, and which has been described in 

 detail in Prof. Bonney's " Cambridgeshire Geology," and in Mr. 

 Skertchly's " Geology of the Fenland." 



