Chemistry and Physics. 487 



become somewhat popular. Whether this course is the best one 

 or not is a matter of opinion, but it appears to the reviewer that 

 qualitative analysis should be presented in the attitude that it 

 teaches certain facts, for instance, the fact that acids, bases and 

 salts readily exchange their radicals in solution, thus leading to 

 the precipitation of insoluble compounds, and the removal of 

 volatile compounds by evaporation. When these facts have been 

 grasped it may be desirable to call attention to the ionic theory 

 as a method of explaining these facts ; but to base facts upon a 

 theory is not the logical way, for the theory is actually derived 

 from such facts. h. l. w. 



5. A Suggested Method of Ascertaining the Existence of Chlo- 

 rophyll on Planets. — N. Umow suggests the application of the 

 following method : Paper discs covered with chlorophyll reflect 

 the light of a Nernst lamp into an optical apparatus consisting of 

 an objective, a cylindrical lens, a Savart polariscope with a tour- 

 maline plate ; a direct vision spectroscope and finally a small 

 power telescope in a reversed position. The Savart striae run 

 horizontally through the spectrum and are modified in a striking 

 way by the presence of the chlorophyll. The author gives a 

 figure of the appearance which is presented ; and since he has 

 not the proper facilities recommends the method to astronomers. 

 — Physik. Zeitschrift, April 15, 1909, pp. 259-260. j. t. 



6. Condensation of the Radium Emanation. — Rutherford 

 and Soddy showed in 1903 that the radium emanation condensed 

 from the gases with which it was mixed at a temperature of 

 about — 150° C. Rutherford has now worked with larger quan- 

 tities of radium. He finds that the density of the liquid emana- 

 tion is not less than 5, and its atomic weight 222. The absence 

 of combining properties indicate that it is an inert gas, the 

 heaviest known having a density of 111 times that of hydrogen. 

 (Cf. No. 1 on p. 485.)— Phil. Mag., May, 1909, pp. 723-729. j. t. 



7. Electric Origin of Molecular Attraction. — William Suther- 

 land has previously brought forward evidence in support of the 

 view that molecular attraction varies as the fourth power. He 

 considers, in connection with this view, the attraction between 

 two small magnets, directed along a straight line which also 

 varies as the fourth power; and is led to consider a bipolar elec- 

 tric attraction of molecules, with reference to cohesion. He 

 alludes to papers by Fessenden and Reinganum, on the electrical 

 origin of cohesion which might arise from a bipolar condition of 

 molecules. Sutherland points out that there is no theoretical or 

 experimental justification of the literal truth of Fessenden's 

 assumption for gases. Nevertheless, J. E. Mills has discovered a 

 remarkable relation which seems to justify the assumption com- 

 pletely. Mills' application of his law to gravitation was errone- 

 ous, but the law can be applied to electric attraction, and is 

 expressed as follows : The total potential energy of a number of 

 like molecules is the same as if each caused its own domain to be 

 uniformly electrized with an electric moment proportional to the 



