578 Scientific Intelligence. 



scribed in the author's own words : "I finally adopted the plan 

 of describing a connected series of investigations, laying special 

 stress on the observational methods employed, in the hope of 

 explaining clearty how the problem of stellar evolution is 

 studied. . . . The various researches described are chosen 

 rather arbitrarily, in some cases' with more regard for my per- 

 sonal acquaintance with the facts than because of their intrinsic 

 importance." 



While the main problem is that given in the title, the greater 

 part of Professor Hale's latest book has been directed towards the 

 sun. He has shown not a little ingenuity in devising and con- 

 structing instruments for the observation of a body which gives 

 us so much heat that accurate work is seriously interfered with 

 by the distortion of the lenses and mirrors employed. These 

 devices, old and new, are described in nearly half of the printed 

 matter of the volume with the reasons which have led to their 

 adoption. Interspersed are chapters on the hypotheses which it 

 is desired to test. The author has also considered those who 

 have only a general acquaintance with scientific methods, and he 

 outlines briefly the main principles of his subject, — spectrum anal- 

 ysis, evolution of a star, the construction of a telescope, and so on. 



In such a volume, criticism of details is unnecessary especially 

 when so many of the questions at issue are still sub judice. It is 

 to be recommended to those who wish to know the facts and 

 problems set forth in an attractive manner ; parts of it will 

 appeal to the trained student desiring a brief account of the latest 

 developments ; and perhaps more than all, the suggestiveness 

 which characterizes Professor Hale's work will be welcome to 

 those who are looking for problems to solve. To mention only 

 a single instance of the latter, we have yet to find out how to 

 make a quantitative estimation of time changes on the solar sur- 

 face with some approach to accuracy. 



About half the thickness of the volume is taken up with excel- 

 lent photographs, and the somewhat rambling order in which the 

 various subjects are treated will not be found an objection if full 

 use is made of the index. The latter would have been more con- 

 veniently placed at the end instead of the middle just before the 

 plates, which are placed together in the second half of the book. 



ERNEST W. BROWN. 



12. Die Korpuskulartheorie der Materie / von Dr. J. J. Thom- 

 son, Autorisierte Ubersetzung von G. Siebert. Pp. vii + 166. 

 Braunschweig, 1908 (F. Yieweg & Sohn). — This is the German- 

 translation of Professor Thomson's latest book, which is an 

 amplification of a course of lectures given in 1906 at the Royal 

 Institution. It is similar in character to the author's Silliman 

 Lectures, "Electricity and Matter," delivered at New Haven in 

 1903, and is essentially a sequel to them ; the rapid progress in 

 the development of the electrical theory of matter is strikingly 

 illustrated, by a comparison of the two books. The first three 

 chapters give a. brief account of the properties of the electron or 



