Chemistry and Physics. 79 



results as far as the photographic activity is concerned, but he 

 finds, when the products are tested by means of the electrometer, 

 that the UrX part is almost inactive while the uranium part 

 retains its activity. The conclusion is reached, agreeing with the 

 observations of Rutherford, that uranium possesses two distinct 

 kinds of radiation, one of which (a) is absorbed very readily even 

 by gases and the other (/?) is very penetrating in its nature. It 

 was found that after the cathodic (j3) rays have been removed by 

 chemical means they are gradually regenerated in the uranium 

 salt. — Chem. JVetos, lxxxvi, 199. h. l. w. 



3. Radio- activity of Thorium. — In connection with the descrip- 

 tion of very elaborate researches on the subject, Rutherford 

 and Soddy mention some interesting facts in regard to thorium 

 radio-activity. Besides being active in the same way as uranium 

 compounds, the compounds of thorium continuously emit a gas 

 which possesses the property of temporary radio-activity. This 

 emanation is the source of rays which ionize gases and act upon 

 photographic films. The emanation excites radio-activity on all 

 surfaces with which it comes in contact, and such surfaces behave 

 as if they were covered with an invisible layer of intensely active 

 material. If thoria is exposed to a strong electric field, the 

 excited radio-activity is entirely confined to the negatively 

 charged surface, and in this way it is possible to concentrate it 

 on a very small area. The excited radio-activity is removed by 

 rubbing, or by the action of acids. If the acids be then evapo- 

 rated, the radio-activity remains on the dish. It appears from 

 these facts that minute quantities of special kinds of matter in the 

 radio-active state are given off by thorium compounds. — Phil. 

 Mag., 1902, 370. h. l. w. 



4. Metallurgical Laboratory Notes; by Henry M. Howe. 

 8vo, pp. 140. Boston, 1902 (Boston Testing Laboratories). — 

 This is a course of laboratory instruction for students. The 

 author, very wisely it seems, has avoided the attempt to repro- 

 duce industrial processes as a whole, but has aimed to teach the 

 underlying principles. His reasons for this plan are well put as 

 follows : " For the details of practice are learnt inevitably, spon- 

 taneously, accurately and with the greatest ease in practice itself, 

 but with very great difficulty and distortion in the laboratory. 

 Principles, on the other hand, are what the laboratory teaches 

 most readily and perfectly, and practice least readily and most 

 imperfectly." The book contains a series of very suggestive 

 experiments, many of which are quantitative in their character, 

 and the work evidently marks an advance in metallurgical instruc- 

 tion, h. l. w. 



5. The Analysis of Steel-works Materials ; by Brearley and 

 Ibbotsox. 8vo, pp. 501. London, 1902 (Longmans, Green and 

 Co.). — The wide scope of this book is seen from the following list 

 of the parts into which it is divided : The analysis of steel, of 

 pig-iron, of steel-making alloys ; rapid analysis at the furnace ; 

 the analysis of ores, of refractory materials, of slags, of fuel ; 



