August 9, 1912] 



SCIENCE 



187 



he ■will need to be somewhat industrious and 

 patient. This may be said with full appre- 

 ciation of the excellent list of references that 

 is added at the close of every chapter. But 

 the non-technical reader, if he becomes impa- 

 tient because the demands of the student are 

 not fulfilled, becomes reassured when he looks 

 back into the preface; for he has forgotten 

 that "the book has been prepared for the 

 worker in applied optics rather than the 

 student." 



The next chapter is on the design and test- 

 ing of optical systems. This subject likewise 

 is mathematical, and the treatment is open to 

 some pedagogical criticism ; but the amount of 

 information, non-mathematical in form, is in- 

 creasing; and the individuality of the author 

 as a careful and resourceful investigator is 

 becoming more clearly manifest. Prior to the 

 publication of this book he had become well 

 known through his published work in several 

 tranches of optics ; and for development in his 

 chosen field it would be hard to find a better 

 place than the Bureau of Standards. 



From this point on, the successive chapters 

 contain less material requiring skiU in the art 

 of presentation, but much that reveals the 

 author's rich experience in the optical labora- 

 tory. He is at home in the discussion of 

 optical instruments and the conditions under 

 which they may be used to best advantage, in 

 the methods of measuring refraction, and in 

 the intricacies of physiological optics. In the 

 treatment of colorimetry, illumination, pho- 

 tometry and spectrophotometry, radiometry 

 and spectroradiometry, polarimetric analysis, 

 plate grain and sensitometry, and interferom- 

 etry, he has evidently worked with great skill 

 and ardor, enjoying the work thoroughly. He 

 has gleaned information from all possible 

 sources, and has recorded in small compass 

 what might well have been greatly expanded. 

 The present volume is indeed apparently ten- 

 tative. This is indicated in the preface, where 

 the enterprise is referred to as an entering 

 wedge, since the full treatment of applied 

 optics " could be adequately treated only in a 

 number of volumes by a dozen specialists." 

 It is to be hoped that these volumes will ap- 

 pear in due time, but that upon them better 



editorial care may be applied than is mani- 

 fested in this initial volume. 



W. LeC. Stevens 

 Lexington, Va., July 10, 1912 



Distribution and Origin of Life in America. 



By Egbert Francis Schaeff. New York, 



The Macmillan Company. 1912. Pp. xvi + 



497, 21 maps. 



Students of zoogeography the world over 

 will welcome this book, for the author's mas- 

 terful treatment of the European fauna' leads 

 one to expect that he will bring to it the same 

 wealth of ideas, sound knowledge and good 

 judgment that characterize his previous work. 

 In the- opinion of the reviewer this expectation 

 is fulfilled. The data are presented about as 

 exhaustively as is possible in a work of this 

 size, the opinions of different students are 

 summarized in an unbiased way, the gener- 

 alizations and data are carefully weighed, and 

 the author's conclusions are clearly expressed. 



Very little but good can be said of the gen- 

 eral method of attack. Dr. Scharff fully 

 realizes that problems of origin and dispersal 

 can not be approached from the standpoint of 

 zoogeographical regions, and no space is given 

 to this subject. He analyzes separately the 

 faunas of different parts of North, Central 

 and South America, and of the Antilles, Ber- 

 mudas, Galapagos and other American islands, 

 and endeavors to discover the sources and 

 migration routes of the different elements. 

 He goes to some length to show the very small 

 role which he believes accidental dispersal 

 plays in the populating of distant lands — a 

 method that has been clearly overestimated 

 since the classic works of Darwin and Wallace 

 — and expresses the conviction that the facts 

 of North American zoogeography can best be 

 interpreted by postulating various land 

 bridges. When such land bridges are appar- 

 ently called for, the author endeavors to gather 

 evidence for them from botany, geology and 

 paleontology. 



Dr. Scharff argues for the existence in pre- 

 Glacial or Glacial times of a North Atlantic 

 land bridge, connecting Scotland, Iceland, 

 Greenland, and Labrador, and a North Pacific 



^ ' ' The History of the European Fauna. ' ' 



