January 7, 1916] 



SCIENCE 



29 



logical terms senescence does not follow an un- 

 broken course. 



Non-energistic formulfe do not appeal to the 

 author. In fact he seems to delight in show- 

 ing his antagonism toward them. For in- 

 stance, he says that " attempts to connect par- 

 ticular facts with particular chromosomes or 

 parts of chromosomes are not at the present, 

 properly speaking, scientific hypotheses." This 

 and similar statements leave no doubt aa to 

 the direction of Professor Child's interest. 

 They may, unfortunately, keep some readers 

 from a fair consideration of the very valuable 

 results of his work. 



The extent of the ground covered in the book 

 is well indicated by the titles of the five parts. 

 I. The Problem of Organic Constitution. II. 

 An Experimental Study of Physiological 

 Senescence and Rejuvenescence in the Lower 

 Animals. III. Individualism and Reproduc- 

 tion in Relation to the Age Cycle. IV. Ga- 

 metic Reproduction in Relation to the Age 

 Cycle. V. Theoretical and Critical. About 

 half of the space is devoted to the experiments 

 of the author and the greater part of the ob- 

 servations appear here for the first time. 



The importance of the facts and their gen- 

 eral interest make it a matter for congratula- 

 tion that they have appeared in this connected 

 form rather than in separate papers. The 

 book will be welcomed by all those interested 

 in the problem of development. 



Charles Zeleny 



Land Magnetic Observations, 1911-191S and 

 Reports on Special Researches. By L. A. 

 Bauer and J. A. Fleming. Washington, 

 D. C, 1915. Publication ISTo. 175, Vol. 2, 

 of the Carnegie Institution of Washington. 

 4to. Pp. V -1-278. 13 plates, 9 text -figures. 

 This is the second volume of the " Re- 

 searches of the Department of Terrestrial Mag- 

 netism," the first volume having dealt with the 

 magnetic observations on land from 1905 to 

 1910. Some idea of the magnitude of the 

 work carried out under Dr. Bauer's energetic 

 leadership can be gained from the statement 

 that during the eight years following the 

 founding of the department the various expe- 



ditions by land and sea covered in all nearly 

 a million miles. Observations were made in 

 103 different countries and island groups. 

 The results of these expeditions and of special 

 investigations have been embodied in about 

 125 articles and publications. It is now ex- 

 pected that one of the chief objects for which 

 the Department of Terrestrial Magnetism was 

 founded, the general magnetic survey of the 

 globe between latitudes 70° N". and 65° S., 

 will be completed in 1916. Up to the present 

 time this remarkable achievement has been 

 accomplished without loss of life. 



In view of the ever-changing values of the 

 magnetic elements and of our imperfect 

 knowledge of the secular variation in many 

 parts of the earth, it is of immense importance 

 in the analysis of the earth's magnetic field, 

 and thereby ultimately to the navigator and 

 surveyor, that magnetic data be secured for 

 the whole globe at as nearly the same epoch 

 as possible. As has often been remarked, we 

 can never hope to know much about the 

 magnetic field in a vertical direction above or 

 below the earth's surface. Hence a minute 

 and accurate knowledge of the magnetic field 

 over the surface to which we are confined is of 

 all the more importance. It will be greatly to 

 the credit of the Carnegie Institution to have 

 accomplished the task in less than a decade. 

 No cooperation of civilized governments could 

 be expected to do this. It is precisely in work 

 of this sort that a richly endowed private in- 

 stitution can render its greatest service. 



The first part of the volume is devoted to 

 a description of instruments, with their cor- 

 rections, and the magnetic standards finally 

 adopted. Two new universal types of mag- 

 netometer have been developed by the depart- 

 ment, and seven complete instruments have 

 been constructed in the department's shop. 

 Many persons not directly interested in mag- 

 netism would find it to their advantage to ex- 

 amine the ingenuity and elegance of some of 

 the instrumental details. 



The old-fashioned dip circle, with its eccen- 

 tricities both literal and figurative, has largely 

 given place to the earth inductor. Nothing is 

 said about trouble from thermo-electric cur- 



