October i, 1891] 



NATURE 



517 



The sections on the metamorphism of minerals, and on 

 the formation of minerals in nature, will be found of 

 great interest to the petrologist. Here are described the 

 effects on minerals of heat, of gases at high temperatures, 

 of fusion, of fused magmas, of water containing carbonic 

 acid, &c. In the last section, dealing with the composi- 

 tion and constitution of minerals, the present imperfect 

 state of our knowledge is brought prominently to light. 

 The battle is still being fought between the so-called 

 chemical, liquid, and crystal molecule ; between consti- 

 tutional and empirical formulae. Mineralogists are be- 

 ginning to understand that it is impracticable to attempt 

 to use for complicated minerals principles which are only 

 applicable to volatile organic compounds, and the idea 

 is gaining ground that many minerals are molecular 

 compounds only capable of existing in the solid state, 

 the crystal molecule being built up of different chemical 

 molecules. 



The author intends to supplement the present work 

 by another, entitled " Chemical Mineralogy," in which 

 the composition, synthesis, &c., of each individual mineral 

 will be treated more particularly. The present volume 

 is intended as quite a general treatise on the subject of 

 mineral chemistry ; in fact, we cannot help thinking that 

 in many parts the treatment is far too general, and that 

 the book has been partially sacrificed for the sake of the 

 volume that is to follow. The value of the book is in- 

 creased by the lists of references to the literature which 

 precede each section. G. T. P. 



OUR BOOK SHELF. 



Bush Friends in Tasmania : Native Flowers, Fruits, and 

 Insects, drawn from Nature, with Prose Descriptions 

 and Illustrations in Verse. By Louisa A. Meredith. 

 Executed by Vincent Brooks, Day, and Son. (London 

 and New York : Macmillan and Co., 1891.) 

 Upwards of thirty years ago Mrs. Meredith gave the 

 world a volume containing admirable coloured figures of 

 a selection from the many beautiful plants and insects 

 that inhabit her island home, Tasmania ; and now, in the 

 evening of a long life, she has travelled to the old country 

 to publish a second volume, which is to be the last. Her 

 purpose achieved, she " hopes to return and end her days 

 among her children in that pleasant colony," which has 

 given a brighter home to so many of our kith and kin. 

 Lovers of the beauties of Nature in this country will 

 find much pleasure and instruction in this second volume 

 from that talented lady's pen and pencil, and will be able 

 thereby to form some conception of the totally different 

 kind of vegetation from our own that clothes this remote 

 southern island, as well as the great Australian country, 

 for it is only a part of the same flora. To the colonists 

 themselves the book will be even more attractive, as 

 a means of becoming acquainted with the names and 

 affinities of the beautiful objects with which they are sur- 

 rounded. It will also, it is to be hoped, teach them to 

 prize and preserve these rare and precious gifts. Like all 

 true lovers of Nature, Mrs. Meredith deplores the wanton 

 destruction of rare flowers near Hobart by thoughtless 

 or greedy persons whose only aim seems to be quantity. 



The botanical part of Mrs. Meredith's book is per- 

 fectly trustworthy, having been scrutinized by so eminent 

 an authority as Sir Joseph Hooker ; and Prof. Westwood 

 furnished the names of the insects. 



Some of the poems have a special interest in connection 

 with the early history of the settlement of Tasmania. 



NO. I 144, VOL. 44] 



Notably an "Old Story" of 1834, which narrates the 

 massacre by aborigines of a whole family— father, mother, 

 and seven children. 



The Elementary Geometry of Conies, with a Chapter on 

 the Line Infinity. By C. Taylor, D.D, (Cambridge: 

 Deighton, Bell, and Co., 1891.) 



Dr. Taylor's "Geometry of Conies" is so well known, 

 and has met with such acceptance — this is the seventh 

 edition, revised — that we are not called upon to give a 

 detailed account of it. Two additions, however, claim a 

 brief notice. A new chapter (xii.) contains " a course for 

 beginners," in which students who prefer to take the 

 three conies separately have a selection of articles, from 

 the text, indicated for a first reading. Further, a set of 

 duplicate proofs is given in outline, the completion of 

 which is left to the reader. The other novelty (chapter 

 xi.) is " a new treatment of the hyperbola." This is the 

 expansion of a paper which the author read before the 

 Association for the Improvement of Geometrical Teach- 

 ing, in January 1890, and of which the President (Prof. 

 Minchin) is reported to have said : " One thing thnt 

 struck him about the paper was, that Dr. Taylor arrived 

 at points on the curve in a very much more rapid and 

 simple way than any he had previously known of" The 

 author remarks that it is in accordance with the historical 

 order to draw the asymptotes before tracing the curve, 

 for the hyperbola seems to have been discovered from its 

 "equation" (A.I.G.T. Report, 1890, p. 12). 



It is somewhat remarkable that Dr. Taylor does not 

 give a proof of this equation. We append one. Taking 

 his figure on p. 103, we draw the second asymptote. 

 Now draw PM parallel to Cp, cutting the axis in K, and 

 the second asymptote in M : then, 



4CM 



MP = 4MK . MP = (MP-f MK)2-(MP-MK)2 

 = C/^ - KP2 = \\pW - PN-) (where X is a 



constant) 

 X2(S/=' - SP-) 

 \^(S/-;>Y*) 



X2 . SY2 = Ca2 = rt2 _j_ ^2. 



Again, let PQ be any chord meeting the asymptotes in 

 p, q ; and let Q/, Pw, parallel to Qp, Qq respectively, 

 meet those lines in /, m. Then we have 



Qm 



pm Cp 





hence 



Vq _Q.m _ CI _pQ., 

 ^q Q7 P;« P/' 



VP = (Iq, and ^q = /Q. 



Other properties occur to us, but the above are classic 

 properties of the curve, and the wonder is that Dr. Taylor 

 has not applied his new treatment to obtain them. There 

 is no suggestion that they can be so obtained, either in 

 the book or the original paper as printed in the A.I.G.T. 

 Report. R. T. 



Les^ Engrais Chimiques. Par Georges Ville. Septi^me 

 Edition. (Paris: M. Engel, 1890.) 



This is a new edition of the author's lectures on chemical 

 manures, which were first published in 1868, and which 

 have been translated into seven languages. An English 

 edition, by Mr. Crookes, was published in 1879. The 

 sixth French edition has been out of print for about ten 

 years, and during that time the price of chemical manures 

 has considerably declined, on an average about 40 per 

 cent. On this account the author has introduced, at the 

 end of the volume, a chapter containing new formulae for 

 mixed manures, based on considerations of market value 

 and more complete knowledge of the requirements of 



