June 16, 1911] 



SCIENCE 



935 



correct acidity "where it now exists or where it 

 may develop. The phosphorus is needed solely for 

 its plant food value. The supply of organic mat- 

 ter must be renewed to provide nitrogen from its 

 decomposition and to make available the potas- 

 sium and other essential elements contained in the 

 soil in abundance, as well as to liberate phos- 

 phorus from the raw mineral phosphate naturally 

 contained in or applied to the soil. 



It should be said here that throughout the 

 work Professor Hopkins is concerned only 

 with general farming, not with intensive 

 agriculture where other fertilizers can be 

 used with profit and must be if largest results 

 are secured. 



Chapters are given to the discussion of 

 limestone, of phosphorus and of organic mat- 

 ter and nitrogen, as to their function, quanti- 

 tative needs and maintenance. Then follow 

 chapters on rotation systems for grain farm- 

 ing, live stock farming, the use of phosphorus 

 in different forms and finally theories con- 

 cerning soil fertility. The subject-matter of 

 these chapters is of the greatest importance; 

 the views presented are in the main funda- 

 mentally sound; they are well presented, and 

 must have a very important influence in ad- 

 vancing agriculture in the United States. 



Part III. contains an admirable digest of 

 the more important field experiments bearing 

 upon permanent agriculture, conducted at 

 Eothamsted, England; in Pennsylvania, Ohio, 

 Illinois, Minnesota, in the south and in 

 Canada, pointing out their bearing upon the 

 views expressed in the preceding sections. 



Professor Hopkins has succeeded in pro- 

 ducing a worthy companion volume to Hil- 

 gard's great work " Soils." 



F. H. King 



Madison, Wis., 

 May 16, 1911 



The Ice Age in North America and its Bear- 

 ing upon the Antiquity of Man. By G. 

 Frederick "Wright. Fifth edition, revised 

 and enlarged. Pp. 800. 200 illustrations. 

 8vo, cloth. 



The popularity of Wright's " Ice Age " is 

 sufficiently attested by the fact that the fifth 

 edition is now published under date of De- 



cember 22, 1910, enlarged and embellished 

 with many new and interesting illustrations. 

 The value of Professor Wright's work con- 

 sists principally in the illustrations and de- 

 scriptions he gives of glacial phenomena not 

 only in North America, but in other portions 

 of the world. The main criticism of this 

 v\'ork, which has many good features, is that 

 its author is too credulous, and has thus per- 

 mitted many exploded " chestnuts " like the 

 '• Calaveras Skull," the " Lansing Skeleton " 

 and the " Nampa Image " to find in him a 

 defender of their antiquity. This tendency 

 of Professor Wright is unfortunate, since it 

 of itself throws doubt upon his power of crit- 

 ical discrimination in analyzing evidence 

 pro and con in matters of geologic contro- 

 versy. It is possible that Professor Wright's 

 theological beliefs have unconsciously biased 

 his judgment in matters pertaining to the 

 age of the earth, and to the date of the glacial 

 epoch. In spite of these defects, however. 

 Professor Wright's " Ice Age in North Amer- 

 ica " will prove a useful work in enlisting 

 popular attention, and study of these most 

 interesting phenomena connected with the 

 Pleistocene glaciation. 



I. C. White 



SPECIAL ARTICLES 



A SCALE FOR MEASURING THE IIERIT OF ENGLISH 

 WRITING 



One inch may be said to be equal to another 

 inch from any one of three lines of evidence. 

 If the two are compared by a hundred experts, 

 (1) the experts will all report the two as in- 

 distinguishable; or (2) if some of them do, by 

 microscope, micrometer or the like, find a dif- 

 ference of a trifle plus or minus, the number 

 finding the first inch plus will equal the num- 

 ber finding it minus; or (3) if each man is 

 forced to report a difference, haK will find the 

 first inch plus and haK minus. 



One specimen of English writing may be 

 said to be equal to another from the second or 

 third lines of argument, the only logical dif- 

 ference between equating the two lengths and 

 equating the two specimens of writing being 

 that the variability of expert judges in the 



