52 



NA TURE 



[NoVEMBEK 15, 1894 



Gravitation " is correct ; but the kilogramme weight 

 remains the same throughout the universe. 



But if a balance could be constructed with its fulcrum 

 somewhere in the Azores, and the scale pans hanging 

 over Paris and Washington, then i kilogramme at Paris 

 would equilibrate i •00092 kilogramme at Washington 

 <p. 2S6). 



It is sometimes asserted in our school-books on 

 Mechanics that a pound weight, if carried to the surface 

 of the Sun, would weigh about 30 pounds ; but if a 

 balance could be made to stretch between the surfaces 

 of the Earth and of the Sun, then a pound weight at the 

 Sun's end would be equilibrated by 30 pounds at our end ; 

 so that it is equally true to say that a pound weight on 

 the Sun will weigh 30 pounds on the Earth. 



Prof. Mach would perform a great service if he would 

 extend his criticisms on the usage of the word pondus 

 by Huygens, Leibnitz, Wallis, &c., to modern times, as 

 great mystifications exist at the present day. 



The C.G.S. system of units is explained by Mr. Pierce 

 on p. 385. These units are much too minute except for 

 recording delicate physical measurement. If Prof. 

 Johnstone Stoney's amendment of the M.K.S. (metre- 

 kilogramme-second) system had been adopted, we should 

 have a system incorporating the joule, watt, volt, ohm, 

 and ampi-re as units ; it is not too jate to make the 

 change ; the disadvantage that the density of water is 

 1000 in this system is more apparent than real. 



Although the double system of natural laws mentioned 

 by Rankine is now exploded, we still have a double 

 system of instruction in mechanical text-books, one theo- 

 retical, geometrical, rational ; the other practical, me- 

 chanical, empirical, discoverable by experience. It 

 should be the object of modern science to break down 

 the barriers between these two systems, and to treat the 

 subject of mechanics from one point of view. Instead 

 of this, the gap between the two systems seems to be an 

 increasing one, insomuch that Prof. A. B. W. Kennedy, 

 m his inaugural address to Section G of the British 

 Association at Oxford, demanded for young engineers a 

 course of instruction in mathematics entirely different to 

 that imparted at present in our schools and colleges. 



Some remarks at the end of Prof. Kleins Sixth 

 " Evanston Colloquium " may be consulted as bearing on 

 this question. 



A careful study of Prof. Mach's work, and a treat- 

 ment with more experimental illustration, on the lines 

 laid down in the interesting diagrams of his Science of 

 Mechanics, will do much to revivify theoretical Mechan- 

 ical Science, as developed from the elements by rigorous 

 logical ueaiment. A. G. Greenhill. 



NEIVTI/'S INORGANIC CHEMISTRY. 

 A Text-book of Inorganic Chemistry. By G. S. Newth, 

 P.I.C., K.CS. Pp. xiii. 667. (London : Longmans, 

 Green, and Co., 1894.) 



THE author states in the preface, that the arrange- 

 ment of the course of elementary instruction in 

 chemistry, which is given in this book, is based on the 

 periodic classification of the elements. The properties 

 of four elements, hyiiroi^en, ii.ijxen, iiitnigen, and carbon, 

 and the properties of many compounds of these elements, 

 NO. 1307, VOL. 51] 



are considered before the systematic study is entered on, 

 of the groups into which the elements are divided by the 

 application of the periodic law. Then follow chapters 

 wherein the members of the various groups of elements, 

 and the chief compounds of these elements, are described. 

 To this descriptive part of the book are prefixed fifteen 

 chapters of " introductory outlines," constituting " a brief 

 sketch of the fundamental principles and theories upon 

 which the science of modern chemistry is built." In his 

 directions to students using the book, the author says that 

 a start should be made by reading carefully the chapters 

 dealing with chemical change, elements and compounds, 

 nomenclature, and symbols ; that the four typical ele- 

 ments — hydrogen, oxygen, nitrogen, and carbon — should 

 thenbe studied ; and that, as this study is proceeding, the 

 remaining chapters of the "introductory outlines" 

 should be mastered. 



It seems to me that the method of the author is 

 radically wrong. Descriptive statements of facts ought, 

 surely, neither to precede, nor to follow, but to accompany, 

 the reasoning on these facts whereby general principles 

 are gained. 



The author's treatment of chemistry implies that " the 

 science of modern chemistry is built" on the foundation 

 of such generalisations as those stated in his " intro- 

 ductory outlines," and that detailed descriptions of the 

 properties of certain kinds of matter called elements 

 and compounds constitute the science that is raised on 

 this foundation. Would it not be more advisable so to 

 treat the subject as to show thit chemistry rests oncer- 

 lain definite natural facts, but that only when these facts 

 are compared, contrasted, and classified, does a scientific 

 knowledge of them begin ? 



The descriptions in this book of the members of each 

 group of elements seem to me to be exceedingly well 

 done; many portionsof the chapters treating of principles 

 and theories, notably the pages which deal with the laws 

 of chemical combination, are admirable ; nevertheless 

 the book, as a whole, gives the impression of being un- 

 scientific. The method of the book tends, in my opinion, 

 to perpetuate the vicious and unreal distinction between 

 chemistry and chemical philosophy, a distinction that 

 has probably been as potent as any other cause in 

 stopping the progress of the science. 



The purely descriptive portions of this work are often 

 extremely good, as far as they go. The facts, or rather 

 half-facts, are stated in a clear and orderly way ; care is 

 taken to notice recent work of importance ; the wood- 

 cuts are well executed : but, all this is only the material 

 out of which chemistry is constructed. 



About 130 pages are devoted to statements of the pro- 

 perties of four typical elements— hydrogen, oxygen, 

 nitrogen, and carbon— and of the properties of many 

 compounds of these elements. But hydrogen, oxygen, 

 nitrogen, and carbon are not treated as typical elements 

 they are not compared and contrasted with other ele- 

 ments. After reading the descriptions of these elements 

 and their compounds, and studying the properties of the 

 elements in each of the eight groups of the periodic 

 classification, one still feels unsatisfied. Something is 

 lacking. Surely some fair and fitly fashioned building 

 ought to rise on this broad superstructure. If chemistry 

 IS to be treated as a recitation of disconnected, or artifi- 



