I4S 



NA TURE 



[June 17, 1897 



The task undertaken by the reviewer is a difficult one. 

 I have tried to discover the principles on which the book 

 is constructed, and to follow the method whereby these 

 principles are applied. I trust, and I expect, that the 

 criticisms I make will not be regarded by the author as the 

 flippancies of an irresponsible reviewer, but that he will 

 believe I am serious and as anxious as he is, up to my 

 lights, to promote the study of chemistry. 



What is the subject-matter of chemistry ? If I am 

 justified in taking this book as (among other things) Dr. 

 Tilden's answer to that question, then, in my opinion, the 

 answer is wrong. 



The opening sentence of the Introduction reads well, 



"The science of chemistry has for its object the study 

 of the composition of the materials out of which are 

 formed the earth, the sea, the air, and the organised and 

 living beings which inhabit them. Chemistry also 

 seeks to explain the composition of bodies and their 

 properties." 



If this is taken with the statement on page 12, 



"it is no longer sufficient to determine composition. 

 The aim of the chemist is to ascertain the relation of 

 composition to the physical properties of a body," 



we have a description of the subject - matter of 

 chemistry which seems to me fairly adequate. Would 

 it not have been better to have omitted the word physical 

 in the last sentence of the words quoted ? 



But the book does not fulfil the promise of the Intro- 

 duction. The study of the compositions of bodies ; the 

 study of the properties, especially the reactions, of bodies ; 

 and the study of the connections between the com- 

 positions and the properties of bodies ; that, surely, is 

 the business of chemistry. And the one method by 

 which this business can be conducted successfully is the 

 comparative method. If a student is to acquire a genuine 

 knowledge of that branch of natural science called 

 chemistry, it seems to me he must be led constantly to 

 compare and contrast facts in order that he may be 

 prepared to receive, and comprehend, the generalisations 

 of the science. The foundation cannot be laid firmly 

 unless the builder is thinking of the structure he means to 

 raise upon it. To vary the illustration : if the student of 

 chemistry has shot over him loads of sterilised facts he 

 soon is smothered ; and if attempts are made to restore 

 him by drawing him out now and then and submitting 

 him to a cold douche of theory, the spark of life that was 

 left in him is likely to be washed away. 



After carefully reading much of this book, I am driven 

 to the conclusion that it fails to connect the facts it records 

 with one another, and with the generalisations which rest 

 on the facts, marshal these facts into order, and suggest 

 other facts. Moreover it seems to me that the general- 

 isations of the science are not stated with sufficient 

 fulness, lucidity, and suggestiveness ; that the hypotheses 

 of chemistry are not enunciated in such a way as makes 

 it possible for the student to hold them firmly in his 

 mental grasp, and at the same time to be ready to let 

 them go when they have served their purpose of aiding 

 clear thinking ; and that the theories of chemical science 

 are not brought into just proportion with the facts and 

 the hypotheses which they ought to bind together and to 

 vitalise. 



I admit the enormous difficulty of dealing accurately, 

 NO. 1442, VOL. 56] 



lucidly, and suggestively with the vast quantity of facts 

 that has been accumulated by the labours of generations 

 of chemists. I admit the insuperable difficulty of fitting 

 all the many hypotheses of chemistry into their proper 

 places. I do not deny the impossibility of treating the 

 theories of the science, especially in an elementary book, 

 so as to command the assent of so fractious a fraternity 

 as the chemists. Still I think that a serious and pains- 

 taking effiart should be made by every writer of a 

 manual of chemistry to compare and contrast facts with 

 facts, and to show that the hypotheses and the theories 

 of the science rest on, while they pass beyond, and 

 illuminate, the facts of the science- 

 It would be manifestly unfair, even in a review to which 

 the writer's name is attached, to find such fault with a 

 book as I have found with Dr. Tilden's Manual., without 

 going into some details to justify the fault-finding. 



On pp. 16 to 20 a brief account is given of chemical 

 nomenclature and notation. The facts regarding the 

 compositions of compounds which are conveyed by 

 chemical formula: are expressed in these pages in the 

 language of the theory of atoms. But that theory has 

 not been explained to the student ; it has been sketched 

 in the merest outline only. Indeed the theory could not 

 be explained at this early stage of the student's progress. 

 This method seems to me to be entirely wrong ; I am 

 certain it cannot conduce to correct thinking. 



The Introduction is followed by chapters wherein are 

 recounted, and illustrated, the preparations, and some of 

 the properties, of the non-metallic elements and their 

 more important compounds. These chapters also con- 

 tain lucidly written accounts of those general properties 

 of gases which are of importance to the chemist ; of the 

 structure of flame ; of some of the phenomena of solu- 

 tion ; and of other important matters. Then follow 

 chapters on the laws of combination, the atomic and 

 molecular theory, classification, crystallisation, allotropy 

 and isomerism, heat and chemical affinity, and electro- 

 lysis. These are succeeded by accounts of the prepar- 

 ations and properties of the metals and the compounds 

 of the metals. 



It is not with the chapters or paragraphs which convey 

 information about the elements and their compounds 

 that I find fault. Much, I think one may say most, of 

 what is contained in these chapters is written clearly 

 and accurately ; a selection is made — I think on the 

 whole a good selection — from the enormous number of 

 those facts which are the building stones of the edifice 

 of chemistry. What I complain of is that these building 

 stones are not employed to construct a building ; they 

 are arranged in heaps, and each heap is duly labelled ; — 

 but, that is all. If chemistry is a collection of bundles 

 of information loosely held together by a few strings of 

 generalisation, then the method of this book is excellent. 

 The separate pieces of information are conveyed in clear 

 and accurate terms. But, in my opinion, the binding 

 strings are very fragile and they do not prevent the 

 contents of the bundles from being scattered. 



Many of the chapters which deal with the principles 

 of the science are unsatisfactory. The laws relating to 

 combining proportions are enunciated on pp. 236 to 238 

 These laws are not stated in sharp and decisive terms 

 For instance 



