736 



SCIENCE. 



[N. S. Vol. XVII. No. 436. 



Mr.. Jervis 's mechanical application made 

 the state of the art so complete that his 

 theory has been well-nigh forgotten. 



The stremmatograph confirms the theory 

 that on tracks of stiff rails and joints, loco- 

 motives when drawing their, trains dis- 

 tribute their total load and effects of the 

 expended tractive effort in accordance with 

 a principle of mechanics. In the evolu- 

 tion of American locomotives this principle 

 has received its greatest application, not 

 only in more wheels in the wheel base of 

 the engine, but in that of the tender. 



The decided advantage of being able to 

 distribute the total load of the locomotive 

 through a number of wheel contacts, en- 

 ables a heavy load to be carried without 

 unwarranted injury to the track, by 

 making the forward wheels check deflec- 

 tions under the following driving wheels. 

 The drawbar-pull also becomes of assist- 

 ance in the distribution of the loads on the 

 driving wheels and effects of the expended 

 tractive effort. In this way the combined 

 stability between the locomotive and the 

 superstructure of the permanent way is 

 increased. 



The rail is the most important member 

 of the conservative system either of the 

 superstructure of the track or of the per- 

 manent way. The bending of the rails 

 is produced directly by the moving wheel 

 loads, and the tension under one wheel 

 contact can not take place without pro- 

 ducing compression at some other point. 

 Therefore, bending in either direction is 

 resisted by the metal, which helps dis- 

 tribute the load to a longer portion of the 

 track than is possible on lighter rails. 



The combined stability, efficiency and 

 capacity between the locomotive, rolling 

 stock and the permanent way increase in 

 a faster ratio than the direct stiffness be- 

 tween two sections of rails. This is shown 

 by the great increase in the weight of the 



locomotives and ears in the last few years, 

 running over the same road-beds which 

 were formerly laid with light rails. 



The stresses of the specific deflections of 

 the different wheels of the locomotive run- 

 ning over a flexible track are of necessity 

 quite irregular. The irregular application 

 of steam also makes an irregular distribu- 

 tion of the stresses per revolution. 



As the smoothness of the track has in- 

 creased, the realized coefficient of adhesion 

 of the system of the driving-wheel base of 

 the locomotives has also increased. 



P. H. Dudley. 



SCIENTtFIO BOOKS. 

 Analytical Chemistry. By F. P. Treadwell. 

 Translated from the second German edition 

 by William T. Hall. Vol. I., ' Qualitative 

 Analysis.' 8vo. Pp. xi + 466. New 

 York, John Wiley & Sons. 1903. 

 There are so many books on qualitative 

 analysis, and so many of them have little 

 reason for existence, that it is a matter of 

 satisfaction to examine one, like the work 

 under consideration, which possesses many 

 features of novelty and excellence. 



The book begins with an introduction ex- 

 plaining general principles, including the law 

 of mass action and the ion theory of Arrhe- 

 nius. While the latter theory is apparently 

 advocated, its influence is shown but little in 

 the book as a whole. For instance, in the 

 first part of the introduction it is stated that 

 a precipitation always takes place when an 

 insoluble substance is formed by means of a 

 ' chemical decomposition,' and, although the 

 part of the book which treats of acid radicals 

 is headed ' Eeactions of the Metalloids 

 (Anions),' the substances dealt with are called 

 ' acids.' This neglect of the inodern theory 

 will be approved by some, but it will be ob- 

 jected to by many. 



The book seems to be particularly good in 

 its clear and full descriptions of qualitative 

 tests. Many new and improved methods are 

 introduced, and the methods adopted are gen- 

 erally very satisfactory. However, the re- 



