146 Scientific Intelligence. 



10. Lehrbuch der Optik ; von Dr. Paul Drude. Zweite 

 erweiterte Auflage. Pp. xvi + 538. Leipzig, 1906 (S. Hirzel). — 

 The preface of this second edition of Drude's Optics was written 

 only eight days before the lamented death of the author and the 

 work was carried through the press by Dr. Kiebitz. The princi- 

 pal changes and additions to the first edition (see this Journal, 

 vol. xiv. p. 68, 1902) are in those portions of the subject to 

 which the recently developed electron theory is especially 

 applicable. The additional material makes about thirty pages ; 

 and a subject index is added. h. a. b. 



II. Geology and Mineralogy. 



1. Maryland Geological Survey : Pliocene and Pleistocene / 

 Wm. Bullock Clark, State Geologist. Pp. 291, pis. 75, figs. 10. 

 Baltimore, 1906 (The Johns Hopkins Press). — The present volume 

 is the third of a series of imports dealing with the systematic 

 geology and paleontology of Maryland and completes the geo- 

 logical history of the Cenozoic. Reports on certain of the earlier 

 periods are well under way. The descriptive portion of the 

 report, pp. 23-138, is by Geo. B. Shattuck. The succeeding 

 chapters are by W. B. Clark, F. A. Lucas, Arthur Hollick and 

 others. The work throughout, as in the previous volumes of 

 this survey, is marked by its scientific accuracy and readable 

 nature. The illustrations are well chosen and well executed. 



Under the general descriptive portion is to be noted the geo- 

 logical map of the four formations of the Pliocene and Pleisto- 

 cene on a scale of eight miles to an inch and the accompanying 

 maps showing the relations of land and water at the time of the 

 making of each formation. The oldest of these four is the 

 Lafayette, believed by Shattuck to be late Pliocene and to repre- 

 sent a subsidence of the Maryland coast to the extent of 500 

 feet. No cliff scarp corresponding to this stage has been 

 detected. Following the Lafayette, repeated oscillations of the 

 strand line have occurred, elevation and erosion separating the 

 epochs of submergence, each of which was less than the preced- 

 ing in vertical range. These movements may be tabulated as 

 follows : 



Probably late Pliocene. Lafayette subsidence to 500 feet. 



Elevation and erosion. 

 Probably early Glacial. Sunderland subsidence to 220 feet. 



Elevation and erosion. 

 Probably middle Glacial. Wicomico subsidence to about 100 



feet. 



Elevation and erosion. 

 Probably close of Glacial. Talbot subsidence to 45 or 50 feet. 



Elevation and erosion. 



Subsidence now in progress. 



