NATURE 



[Nov. 8, 1877 



it has received rigorously the proper exposure, it will be 

 seen that the granulation has not every vvheie the same dis- 

 tinctness, that the parts consisting of well- formed grains 

 appear as currents which circulate so as to circum- 

 scribe spaces where the phenomena present the aspect 

 we have described. But to establish this fact, it is 

 necessary to embrace a considerable portion of trie 

 solar disc, and it is this which it is impossible to realise 

 when we look at the sun in a very powerful instrument 

 the field of which is, by the very fact of its power, very 

 small. In these conditions we may very easily conclude 

 that there exist portions where the granulation ceases to 

 be distinct or even visible ; but it is impossible to suppose 

 that this fact is connected with a general system. 



We have written enough to show that when the daily 

 history of the sun comes to be recorded another method 

 and another point of view have now been added as the 

 first fruits of Dr. Janssen's labours in his new observatory. 



J. Norman Lockyer 



FOWNES' ''MANUAL OF CHEMISTRY" 



Fo7vne^ Manual of Chemistry. Vol. 1 1. Chemistry of 

 Carbon Compounds, or Organic Chemistry. Twelfth 

 Edition. By H. Watts, B.A., F.R.S. (London : 

 Churchill, 1877.) 



ORGANIC chemistry is now progressing with such 

 rapid strides, that a work on this subject becomes 

 antiquated, at least in some parts, in the course of a few 

 years. A new edition of a well known and favourite book 

 must therefore be most welcome to students of this branch 

 of chemical science, and more so when edited by a man 

 whom we may justly call " the English Gmelin." 



The old familiar, bulky Fownes has now been divided 

 into two handy volumes, enabling the editor to devote 

 the same space to the carbon compounds as to inorganic 

 chemistry. 



The arrangement of the subject is in principle almost 

 the same as in the last edition ; organic compounds being 

 divided into hydrocarbons, alcohols, ethers, amido-com- 

 pounds,organo- metallic bodies, acids, &c.,the compounds 

 of each group being arranged in homologous series. 



Physiological chemistry is omitted, and this must be 

 considered as an improvement, as that branch of chemical 

 science now requires special treatment in a separate work. 

 The name of the author is a sufficient guarantee for the 

 soundness of the knowledge which this book imparts, and 

 we hope to see it soon in the hands of numerous students 

 who will find it a most useful and trustworthy guide, 

 embracing as it does the most important recent researches. 

 The book is singularly free from misprints, and the few 

 which we have found can be easily corrected by a student 

 who is accustomed to think for himself. 



As a reviewer is expected to point out any faults, we 

 will do so, but " sine irae et studia," and only for the 

 benefit of the students who will largely use this work. 



Thus we miss an account of the normal sulphuric ethers, 

 which are found by the action of sulphuryl chloride, or 

 oxychloride on the alcohols and phenols. Perhaps these 

 parts were written before the researches we allude to 

 were published, and the same may be the case with 

 phenyl-sulphuric acid, and its homologues, compounds 

 which possess such interest both for the chemist and 



physiologist. To lactide, the author still assigns the 

 old formula C3H4O2, although Henry has proved, by 

 determining its vapour density, that its molecular formula 

 is C6H8O4. On page 285 we find a statement which 

 might lead a beginner in practical work to disappoint- 

 ment, it is there said that '' crude acetyl chloride is 

 purified by heating it with water and dilute soda solu- 

 tion." " Quandoque bonus dormitat Homerus." 



We were much pleased to find that Mr. Watts has 

 given particular attention to the study of isomerism, 

 especially among the derivatives of benzene, and he justly 

 says in the preface : " This part of the subject is here 

 presented in a form in which it has not yet appeared in 

 any English publication, except in the Journal of the 

 Chemical Society," 



Speaking of the disubstitution products of benzene, the 

 following definition is given : " A di-derivative of benzene 

 is para-, ortho-, or meta-, according as it can give rise to, 

 or be formed from, one, two, or three tri- derivatives. 

 This definition is, however, incomplete, and only holds 

 good if in the di- derivative the substituting elements or 

 radicals are the same. For it is easily seen that, to 

 take the most simple case, a para-compound containing 

 two different groups such as paranitrobromobenzene 

 can give rise to or be formed from two different amido- 

 nitrobromobenzenes. The oversight is, however, a matter 

 of small importance, and an attentive student will not be 

 led astray by it. 



The theory of structure or position which Mr. Watts 

 treats so fully has been lately attacked by eminent 

 chemists who seem to overlook or forget the great im- 

 pulse which this theory has given to the progress of 

 organic chemistry. The " modern chemists," as they 

 sneeringly have been called, know well enough that the 

 structural formulte which they use do not pretend to give 

 a picture of the real position of atoms in space, and do 

 not mean more than the parallelogram of forces in me- 

 chanics, i.e., they only express the manner in which the 

 different forces of the atoms attract each other. They 

 fully understand that their present theory, with the pro- 

 gress of science will have to undergo many modifications, 

 and it is not a dogma, but will stand or fall on its own 

 merits. 



The opponents of the modern school remind us of the 

 last followers of the phlogistic theory who got hold of 

 any fact which the antiphlogistonists were not able to 

 explain as a proof that the latter were in the wrong. We 

 can easily imagine how pleased Priestley was when it 

 was found that when heating certain metallic calces with 

 charcoal an inflammable air was formed, whereas, accord- 

 ing to Lavoisier's school, only carbonic acid could be 

 produced. Just in the same way the opponents of the 

 structural theory point out that the existence of four lactic 

 acids is incompatible with it ; and Mr. Watts himself, 

 although a strong adherent of the theory of structure, 

 shirks the discussion of this point, and rusticates one of 

 the four in a foot-note, in which he expresses his doubts 

 as to its existence. 



The recent researches of Wislicenus, however, hardly 

 leave any doubt that four such acids exist. We must 

 confess that we are not able to explain the difference 

 between hydracrylic acid and ethenelactic acid, and quite 

 agree with Mr. Watts that Wislicenus' explanation of the 



