924 



SCIENCE 



[N. S. Vol. XXXIV. No. 887 



Aa is well warranted by its importance, a 

 separate chapter is devoted to the composition 

 and utilization of molasses; Java-molasses, to 

 the study of which the author has given much 

 time and personal attention, receives specific 

 consideration. 



The final section of the book deals with fac- 

 tory-output, calculations and records; exten- 

 sive tables and a satisfactory index conclude 

 the volume. 



This brief outline of the book's contents will 

 indicate in how thorough and painstaking a 

 manner the author has acquitted himself of his 

 self-appointed task. His familiarity with the 

 work of other investigators, with that of his 

 American confreres among others, is amply 

 attested by foot-notes and references scattered 

 throughout the volume. 



The straightforward, lucid style in which 

 this book is written is characteristic of its au- 

 thor and makes its reading a pleasure, nor 

 must the excellent make-up of the publication 

 pass unnoticed — the quality of paper used, its 

 typography, the marginal indices, all certainly 

 merit the appreciation of its readers. 



F. G. WiECHMANN 



An Introduction to the Lie Theory of One- 

 Parameter Groups, with applications to the 

 solution of differential equations. By 

 Abraham Cohen, Ph.D., Associate in 

 Mathematics, Johns Hopkins University. 

 Boston, D. C. Heath & Co. 1911. Pp. iv -f 

 248. Half leather. 



The scope of this attractive little volume 

 may be inferred from its seven chapter head- 

 ings, which are as follows : Lie's theory of 

 one-parameter groups, differential equations 

 of the first order, miscellaneous theorems and 

 geometrical applications, differential equa- 

 tions of the second and higher orders, linear 

 partial differential equations of the first order, 

 ordinary differential equations of the second 

 order and contact transformations. 



In form, binding and paper the present vol- 

 ume is similar to the " Elementary Treatise on 

 Differential Equations," by the same author, 

 published in 1906. In subject matter it forms 



a suitable sequel to this work, but it can be 

 read with a more limited knowledge of differ- 

 ential equations. While it should appeal espe- 

 cially to the student of mathematics who is 

 about to begin graduate work in an American 

 university, it should also prove useful to those 

 who make frequent use of the differential 

 equation in applied fields of mathematics and 

 who desire to look at the subject from the 

 systematizing and clarifying standpoint of 

 group theory. 



The book closes with an appendix contain- 

 ing seven notes, two tables, answers to the ex- 

 amples, and a good index. In these notes sev- 

 eral important subjects are developed for 

 which there was no room in the body of the 

 book. In particular, the m-parameter group of 

 transformations is considered briefly in one 

 of these notes. The two tables contain forms 

 of differential equations of the first and of 

 higher order which are invariant under known 

 groups. 



It is very gratifying to witness the rapid 

 increase of American mathematical literature 

 suitable for students who are just beginning 

 graduate work. Even very good students of 

 mathematics have found the transition period 

 from undergraduate to graduate work dis- 

 couragingly difficult because they were all at 

 once compelled to use foreign literature with 

 an abrupt change of point of view and method 

 of presentation. During the last decade much 

 has been done to remedy this serious draw- 

 back, but there are still many lacunas in this 

 literature. The present volume has reduced 

 by one the number of the most important of 

 these. 



G. A. Miller 



SPECIAL ABTICLES 



CARBON DIOXIDE AT HIGH PRESSURE AND THE 



ARTIFICLiL RIPENING OP PERSIMMONS 



It is already known from the work of Prin- 

 sen-Geerligs (through Gore, 1910) on the 

 fruit of the banana that its astringency dis- 

 appears, without softening of the pulp (meso- 

 carp), when surrounded by an atmosphere de- 

 prived of oxygen. This result suggested to 



