July 6, 191 1] 



NATURE 



cess we suppose the genesis of the moon to have been 

 accomplished, it would be difficult to imagine a body 

 so near the earth not possessing the same external 

 characteristics and passing through similar geological 

 changes. There is some evidence to show that the 

 actual materials that once formed part of the globe 

 were transferred to our satellite, and this probability 

 is strengthened by the agreement between the density 

 of the moon and that of the superficial rocks on the 

 earth. Indeed, as the author reminds us, there are 

 not wanting those who can point to the exact spot 

 where the catastrophe occurred that in times past 

 tore from the earth the eightieth part of its mass. 



The main result of the author's examination is to 

 show the general uniformity of the conviction 

 possessed by all students of the lunar surface that 

 the earth and moon have passed through approxi- 

 mately identical processes of evolution. Prof. 

 Gunther reproduces the speculations of ancient Greek 

 philosophers and continues the theme to modern times. 

 Kepler's "Traum von Monde" and the observations 

 of Galileo form connecting links, with the results 

 derived from lunar cartography. In this newer re- 

 search we start from Hevel and Cassini onwards to 

 the exact methods of Meyer, Lohrmann, Schmidt, and 

 Neville Neison. We are reminded of the artistic work 

 of Nasmyth and Carpenter, of Klein, and of Weinek, 

 and justice is done to their penetrating insight and 

 the ingenuity with which they have pursued their 

 researches. One does not realise how engrossing this 

 subject has proved, how keen has been the attention 

 and the hold it has had upon so many ardent workers, 

 until the whole history is methodically exposed. 



Another chapter is devoted to the results of photo- 

 graphic research, in which the pioneer work of De la 

 Rue, Rutherford, and Draper is reviewed, and the 

 history traced down to the admirable series of pictures 

 issued from the Paris Observatory by MM. Loewy 

 and Puiseux. The last four or five chapters are really 

 the kernel of the whole. Herein are considered the 

 formation of lunar craters, the origin of the bright 

 streaks, the debated question of changes of the sur- 

 face, sufficient in amount to be observed telescopically. 

 The tectonic and orogenic structures here come under 

 review, also, but without much approval, the views 

 of Mr. G. K. Gilbert as to the possibility of the fall of 

 meteors influencing or explaining the external features 

 of our satellite. 



SUBSTITUTION IN BENZENE. 

 Die direkte Einfuhrung von Substitiienlcn in den 

 Bcnzolkcrn. Eiu Beitrag zur Losung des Substi- 

 tutions problems in aromatischen Verbindungen. 

 By Prof. A. F. Holleman. Pp. vi + 516. (Leip- 

 zig: Veit and Co., 1910.) Price 20 marks. 

 IT is well known that the empiric rules of substi- 

 tution, which have been evolved from the study 

 of the aromatic compounds, may enable a chemist to 

 predict roughly the result of such a process ; it is 

 equally well known that not one of these rules is free 

 from exceptions. The absence of any rational theory 

 underlying the process or the lack of novelty in the 

 methods employed may have deterred chemists in 

 NO. 2175, VOL. 8/] 



recent years from following up what was formerly 

 regarded as one of the most attractive lines of inquiry ; 

 but it is quite certain that very little in the way of 

 systematic study, especially of a quantitative char- 

 acter, has been done in this field of research. Yet 

 the process of substitution possesses not merely a 

 theoretical significance; it has a very considerable 

 technical value. The formation of halogen, nitro and 

 sulphonic derivatives of aromatic compounds are 

 among the most familiar technical operations of the 

 colour-maker. 



Though the subject has undoubtedly suffered from 

 neglect, nevertheless a few serious students of the 

 process are to be found. Prof. Holleman and his 

 pupils have for many years devoted themselves to the 

 task of systematising the scattered facts and adding 

 new knowledge by a careful qualitative and quantita- 

 tive studv of these reactions. The volume before us 

 contains not only an account of these inquiries and 

 a critical review of methods and results, but forms 

 at the same time a complete book of reference to all 

 the published observations referring to benzene deriva- 

 tives containing up to three substituents. It is 

 obviously a work of immense labour, but should be 

 invaluable to those engaged in this fundamental 

 branch of organic chemistry. It may possibly also 

 serve to direct more attention to a topic of so much 

 interest. It is impossible in a limited space to give 

 more than an outline indicating the scope of the book. 



The first three chapters contain an account of sub- 

 stitution methods, the quantitative estimation of the 

 products bv chemical and physical means (many of 

 which have been devised in the author's laboratory), 

 and the nature of the di-derivatives formed. 



Chapter iv. contains a compendium of results and 

 a critical review of the rules and theories of orienta- 

 tion. Some of the apparent inconsistencies and con- 

 tradictions in the ordinary rules may be realised from 

 such facts as the following : — The nitration of a halo- 

 gen derivative of benzene containing an atom of 

 fluorine, chlorine, bromine, or iodine follows the 

 ortho-para rule, yet the amount of ortho compound 

 under similar conditions varies from 12 to 37 per 

 cent, in the four cases. In the nitration of benzo- 

 nitrile, nitrobenzene, benzoic acid and its esters, all of 

 which are supposed to follow the meta rule, the first 

 gives exclusively a meta compound, whereas the three 

 fatter yield an amount of ortho compound varying 

 from 6, in the case of nitrobenzene, to 28 per cent, in 

 that of ethyl benzoate. Whilst aniline and dimethyl- 

 aniline under certain conditions give meta or meta and 

 para compounds as chief products, dimethylaniline 

 oxide and nitrous acid give mainly ortho and para 

 derivatives. But perhaps the most striking case is 

 that of acetanilide, which, when nitrated in presence 

 of sulphuric acid, gives 80 per cent, of para, but when 

 acted on by nitrogen pentoxide in a solution of acetic 

 anhydride, forms almost exclusively the ortho deriva- 

 tive. 



The empirical rules which have been drawn up at 

 different times by HCibner, Nolting, Armstrong, 

 Crum-Brown, and Gibson, and Vorlander, are care- 

 fully considered and rejected in turn as inconsistent 

 with the facts, whilst the theories of Armstrong, 



