Chemistry and Physics. 195 



many of the materials described. For instance, little is said 

 about the relative merits or the prices of the various pigments, 

 oils, resins and solvents used in the manufacture of paints and 

 varnishes, although many of them are described. H. l. w. 



5. Outlines of Theoretical Chemistry ; by Frederick H. 

 Getman. 8vo, pp. 467. New York, 1913 (John Wiley & Sons). 

 — This text-book is designed for classes beginning the study of 

 theoretical or physical chemistry. A working knowledge of 

 elementary chemistry and physics is presupposed in the presenta- 

 tion of the subject, although an introductory chapter of 19 pages 

 is devoted to a brief review of the principles with which the stu- 

 dent is assumed to be fairly familiar. These elementary principles 

 include the laws of definite, multiple, and combining proportions, 

 the atomic theory, Avogadro's hypothesis, atomic heats, isomorph- 

 ism, valence, and atomic weights, while the main part of the book 

 is advanced and physical in its character. The presentation is 

 mathematical in its aspect, but the use of calculus has been 

 restricted as far as possible. A good feature is the introduction 

 of many numerical problems for solution by the student. There 

 is a chapter on the electron theory, but the author, unfortunately 

 it appears, has decided against the incorporation of any account 

 of radiochemistry. . h. l. w. 



6. Oxygenin the Sun. — In the year 1896 Runge and Paschen 

 showed that the first triplet of the principal series of the oxygen 

 spectrum agreed in wave-length and relative intensity with three 

 Fraunhofer lines in the solar spectrum. Since there are good 

 reasons why the remaining oxygen lines would not be susceptible 

 of detection in the solar spectrum, the coincidence and character 

 of tbe members of the triplet have been accepted as sufficient 

 proof that oxygen is present in the solar atmosphere. On the 

 other hand, in 1912 Geiger obtained three lines in the arc spec- 

 trum of iron which agreed exactly with the triplet and which he 

 ascribed to iron. If the lines observed by Geiger really owe 

 their origin to iron then the argument of Runge and Paschen is 

 not tenable because experience shows that, when sufficiently high 

 dispersion and spectroscopic resolving power are used, the sepa- 

 rate lines of different elements do not coincide exactly, much less 

 in groups. 



In order to settle the question as to the origin of this triplet 

 the experimental side of the problem has been taken up again by 

 Runge and Paschen. These investigators employed a Rowland 

 concave grating'of 3 meters radius of curvature in conjunction 

 with a concave reflector which sent plane waves upon the grating. 

 By working near the principal normal to the grating a non- 

 astigmatic image of the slit was formed on the photographic 

 plate. Furthermore, by using a photographic objective a non- 

 astigmatic image of the source of light was thrown on the slit of 

 the spectrograph. The first source used was a vertical arc 

 between iron electrodes, the lower rod being the anode. The 

 condensing lens was moved by hand in such a manner as to keep 



