July 2, 1874] 



NATURE 



161 



In a book, however, which must necessarily be intended 

 for use by pupils of very different attainments, it would 

 be difficult to avoid criticisms of this kind, and we think 

 the experiments on the whole judiciously selected and 

 clearly explained. We shall look with interest for the 

 appearance of the second volume, and when finished 

 " Physical Manipulation " will no doubt be considered the 

 best and most complete text-book on the subjects of 

 which it treats. A. W. R. 



OUR BOOK SHELF 



Mineralogy. By F. Rutley, F.G.S. (Murby's Text 

 Books.) 



Mr. Rui'ley's little treatise on mineralogy has the merit 

 of expressing in a clear and simple form the facts that are 

 most wanted to be known by the general student of a 

 science for which a small elementary Enghsh book 

 is needed. The descriptions are concise, and the 

 selection of the matter under each mineral gener- 

 ally good. Mr. Rutley, furthermore, gives some fifty 

 pages of preliminary matter, which, though not always 

 put in the most intelligible form, yet embodies a 

 considerable amount of useful technical teaching in regard 

 to the physical properties of minerals. Mr. Rutley even 

 enters, and very rightly does so, on the subject of optical 

 characters. But in these pages, as in the page on 

 thermo-electricity, the author does not seem to have care- 

 fully revised what he wrote, or he would not have followed 

 other authors in speaking of boracite as a uniaxal crystal, 

 and would hardly have classed the dispersion of light by 

 a diamond with the play of colour exhibited by an opal. 

 Nor is an optic axis correctly described as the only direc- 

 tion by looking along which the doubly refracted images 

 of a spot can be got to coincide, as Mr. Rutley will see if 

 he looks at the spot through two opposite faces of the 

 hexagonal prism of a calcite crystal. He ingeniously en- 

 deavours to indicate the nature of the faces of his crystals 

 by a sort of heraldic hatching and marking. The use of 

 small letters always indicating the character of the faces, 

 as in Des Cloizeaux and other French treatises, might have 

 done this usefully ; Mr. Rutley's puzzling figures will 

 probably only serve to scare away the English student, 

 who needs every allurement to the study of the neglected 

 science of crystallography — a science neglected merely 

 because the rudiments of geometry and trigonometry are 

 not made a necessary par: of every scientific student's 

 education. And it is a significant circumstance in con- 

 nection with this neglect of scientific crystallography, that 

 the geometrical methods and simple notaiion introduced 

 forty years ago by our distinguished fellow-countryman, 

 the first livuig crystallographer, Prof. Miller, are, we 

 believe, untaught in any smgle lecture-room in London. 

 Is England to be the last country to adopt a system made 

 European by Senarmont, Sella, Beer, and Grailich, and 

 which is fast overcoming even in Germany itself a natural 

 prejudice in favour of the more unwieldy, though in its 

 time useful and ingenious, notation of the great Leipsig 

 Professor ? 



Sanitary Arrangements for DivcUin«s, intended for the 



use of Officers of Health, Architects, Builders, and 



Householders. By William Eassie, C.E., &c. (Smith, 



Elder and Co. 1874.) 



This volume gives, in a collected form, a series of papers 



published originally in the Britisli Medical Journal. Its 



object, the author states, is to give "an account of the 



most ordinary sanitary defects in dwelling-houses and 



public institutions, in respect to drainage, water-supply, 



ventilation, warming, and lighting ; " and " to set forth,' 



what he believes, " the most simple and effective 



means of preventing or remedying such defects." He 



thinks it necessary to say further :— " The purpose 

 of this small work is to point out, in the plainest lan- 

 guage, what ought to be done to render ancient and 

 modern houses healthy. I will eschew all extraneous 

 matter, as much as possible, and will not fall into the 

 common practice, better honoured in the breach than the 

 observance, of heading the chapters, or interlarding the 

 matter, with lines from the poets." It is but due to 

 the author to say that he has faithfully avoided this ten- 

 dency "to drop into poetry" on the subject of house- 

 drains, sewers, &c. ; on the plainness of the language, 

 however, we cannot speak very highly. Many house- 

 holders, it is to be feared, will find some difficulty in 

 recognising an S-shaned pipe under the name of a " sig- 

 moid" ; or in appreciating the beauty of a description in 

 which the overflow sewage from a cesspool is said to 

 " debouch into the fields." 



The greater part of the book is occupied with a descrip- 

 tion of the various sanitary appliances for buildings which 

 have from time to time been proposed, or which have 

 been brought into actual use : such as drain-pipes, of 

 which twenty-two different kinds are figured and de- 

 scribed ; traps, of which thirty-six are given ; fire-grates 

 and stoves, &c. In many places, indeed, it reminds us 

 of nothing so much as a manufacturer's or tradesman's 

 catalogue. On the whole, however, this work contains 

 much useful information and many excellent suggestions. 

 On the subject of house-drainage, we are glad to see that 

 Mr. Eassie has adopted and advocates the principle of 

 leading all house-drains into one collecting drain, outside 

 the house if possible, and placing in this main drain an 

 efficient trap, properly ventilated, so as to prevent any of 

 the sewer gases finding their way into the house through 

 the drains or pipes. 



LETTERS TO THE EDITOR 



[ The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. A^o notice is taken of anonymous 

 coinniunicalionsi\ 



Robert Brown and Sprengel 

 In the notice of Mr. Darwin (vol. x. p. So, bottom of 2nd col. ) a 

 mishup has somehow occurred which blunts the point intended to 

 be made prominent and renders the statement untrue. I sup- 

 posed that I had written "And we know from another source 

 that he (Mr. Brown) looked upon Sprengel's ideas as /')' ;/(; litems 

 fantastic. Yet instead," &c. The object was to sliovv liow very 

 near Mr. Brown came to reaching the principle that Nature 

 abhors close-fertilisation in plants, and yet did not reich it at 

 all. The authority for the statement I wished to make will be 

 found in a footnote in Mr. Darwin's book on the " Fertilisation of 

 Orchids," p. 340. Asa Gray 



Cambridge, Mass., June 19 



On the Physical Action taking place at the Mouth cf 

 Organ-pipes 

 The most interesting, and perhaps the most impoitant, fact 

 disclosed in the experimentrd study of the organ-pipe on the air- 

 reed theory is this — that the aeroplastic reed has a law of its 

 own, unique amongst the phenomena heretofore observed in 

 musical vibrations. It may be stated thus — As its arcs of viira- 

 tion are less, its speed is greater. All our knowledge of rods and 

 strings, of plates and membranes, would lead us to expect the 

 usual manifestation of the law of iso;hronism, that in the air-r;ed 

 considered as a free rod fixed at one end and vibrating trans- 

 versely, the law would be observed, " though the amplitude may 

 vary, the times of vibration will be the same." Yet here we 

 meet with its absolute reversal, viz. — the times vary with the ant- 

 pliliide. This information does not rest on theory ; every e; e 

 may verify it. A principle so strange, when first its action was 

 observed, might well lead to disbelief in one's senses, although 

 the mind had by its reasonings led up to the fact and sought for it 

 as the one thing needed to give consistency to theory and maf e 

 it a perfect whole. Familiar as the air-reed had been to me, the 

 one secret had been hidden from my eyes ; seeing, they saw 

 not. Faith in the known mode of activity of the transversely 



