388 



NATURE 



[August 21, 1890 



in particular are somewhat behind in this respect, for the 

 dearth of crystallographers in this country, the home of 

 Miller, one of the greatest names in crystallography, is a 

 subject of general remark among Continental workers in 

 this domain of science. What is required is, first, that 

 chemists shall make practical crystallography, the diffi- 

 culty of becoming skilled in which has been greatly over- 

 estimated, one of the essential accessories of their main 

 subject ; and secondly, that special care be taken never 

 to permit a series of well-crystallizing bodies, differing 

 chemically from each other in an ascertained manner, to 

 escape being thoroughly investigated crystallographically, 

 with the object of discovering what geometrical differ- 

 ences accompany the constitutional ones. 



To those who take up the subject from this standpoint? 

 Dr. Fock's work will be of great assistance in placing 

 before them in a succinct, concise, and very complete 

 manner, the present state of our knowledge. The earlier 

 chapters deal with the history of the growth of the views 

 now entertained as to the nature of the architecture of 

 crystals. Then follow a series of chapters upon the 

 modes of formation of crystals, by resolidification of 

 the fused substance, sublimation and separation from 

 saturated solutions ; upon the complicated influence of 

 water of crystallization upon the geometrical form, and 

 the various theories that have been put forward as to the 

 condition of the water in crystals containing it. The 

 nature of double salts, and the evidence of thermo- 

 chemistry as to the mode of union of the simple salts in 

 the double molecule, are very fully discussed, and form 

 a most interesting chapter. Then follow a series of 

 chapters upon the ultimate structure of crystals, as evi- 

 denced by the mode of formation of crystallites, and the 

 order of growth in larger crystals. 



By far, however, the most interesting portion of the 

 book is that which deals with the relations between the 

 crystalline form and chemical composition of crystals. 

 The development of the theory of isomorphism is very 

 clearly traced from the first observation of De I'lsle, in 

 1772, that the sulphates of copper and iron separated in 

 mixed crystals from a solution of the two, to the latest 

 definition of the theory given by Sohncke with reference 

 to his 65 systems of points. The subject of mixed crystals, 

 and the rules which govern their formation, are entered 

 into at length, and their relations to true isomorphism 

 clearly defined. A very suggestive term, that of " physical 

 isomerism," is given to polymorphism, reminding one 

 forcibly of the similarity between the various forms of the 

 same compound or allotropic forms of elementary sub- 

 stances on the one hand, and the isomerism so 

 characteristic of many of the compounds of carbon on 

 the other. The last few chapters of the book are devoted 

 to a rhume of all the more important researches upon iso- 

 gonism or morphotropy— that is, partial or particular-zone 

 isomorphism. The researches of Groth upon the crystal- 

 lographical relations between the derivatives of benzene 

 naturally take a prominent place in such a description, 

 being, as they were, the first which were instituted in a 

 systematic manner. And here, in spite of many addi- 

 tions which have recently been made in other branches 

 of organic chemistry to our knowledge of such morpho- 

 tropic relationships, the subject must perforce end for 

 the present, until more facts have been accumulated and 

 NO. 1086, VOL. 42] 



observations multiplied. It is not, however, the mere 

 accumulation of records of measurements of isolated 

 compounds which is so much needed, it is the systematic 

 crystallographical investigation of series of compounds 

 whose chemical relationships are indubitably established 

 that will be calculated to throw most light upon the sub- 

 ject. To this end it is earnestly to be desired that British 

 chemists will not merely content themselves, in describing 

 well-crystallizing new compounds, with attaching to them 

 the meaningless terms " prisms " or " tables," but will have 

 their crystallographical characters thoroughly investigated,- 

 and their relationships to other compounds of the same 

 or related series definitely made out. 



A. E. TUTTON. 



OUR BOOK SHELF. 

 British Rainfall, 1889. By G. J. Symons, F.R.S. 



(London: Edward Stanford, 1890.) 

 This work deals with the distribution of rain over the 

 British Isles during the year 1889, as observed at nearly 

 3000 stations in Great Britain and Ireland. The author 

 begins with his usual report for the year, in which he 

 points out rather particularly, the list only dealing with 

 the years 1884-88, that heavy falls of 3, 4 or 5 inches per 

 diem may occur in all parts of the country. Then follows 

 an interesting article on the amount of evaporation, in- 

 cluding illustrations of evaporators and numerous tables. 



Under the heading " Staff of Observers " the volume 

 contains returns from 299 stations which sent no perfect 

 record in 1888, the losses being 181, resulting in a net gain 

 of 118. The author informs us that this is the largest 

 increase since the year 1882 ; and we are glad to see that 

 Scotland, which has been retrograding ever since 1883, 

 has at last improved considerably. 



Coming now to the rainfall and meteorology of the year 

 1889, we have, first, notes of some of the principal pheno- 

 mena, amongst which we may mention the following : — 

 January 6, at Nottingham, an extraordinary thickness 

 (an inch at least) of rime on all the trees, &c. ; June 6, 

 at Cambridge Observatory, severest thunderstorm ever 

 remembered. 



The observers' notes for the months and for the year con- 

 tain some interesting information : — In July, at Finchely, 

 Etchingham Park, there were 22 days of absolute drought 

 followed by 15 wet out of the 20 following days ; in the 

 same month the traffic for a distance of ten miles was 

 suspended on the upper level of the Caledonian Canal 

 owing to the scarcity of water. 



Of the heavy rains in short periods recorded, the highest 

 was that of 3'37 inches per hour, lasting for \i\ minutes, 

 at Petersfield, Compton ; but following this, in Warwick- 

 shire, 3*64 inches fell in i hour 5 minutes— a quantity 

 unequalled at any station in the British Isles for at least 

 ten years. Of the extremes of rainfall for the year, the 

 largest fell at Stye, in Cumberland (152-85 inches), the 

 least at Dingwall, East Ross (i4'5i inches). 



Among the absolute and partial droughts, of the former 

 the longest was at Cargen in Kirkcudbright, where no rain 

 fell between June 8 and July 9, or for 30 clear days ; 

 and of the latter the longest lasted for 45 days from June 

 3, at Portland, Co. Waterford. The definitions of these 

 two kinds of drought are respectively : — Periods of niore 

 than 14 consecutive days absolutely without rain; periods 

 of more than 28 consecutive days, the aggregate rainfall 

 of which does not exceed coi inch per diem. 



With regard to the relation of the total rainfall in 1889 

 to the average, we find that it is 8 per cent, below the true 

 average as well as 13 per cent, below that of 1870-79. 



The general tables of the total rainfall for the year are 

 given, with an explanation of their arrangement. 



