Nov. 15, I $7 7] 



NATURE 



43 



insects, and then, after'noticing the Chermes that attacks 

 that very strong food the larch, we come to a full descrip- 

 tion of Phylloxera vastatrix. The Hemiptera are shortly 

 mentioned, and then the Myriopoda. There is a good 

 picture of Geophilus clinging around its great prey, a 

 large earthworm, and also of a Polydesmus. Amongst 

 the Scorpions the long-armed Phrynus and Gonoleptes, 

 and amongst the Spiders a long Tetragnatha and the 

 extraordinary-bellied Gasteracantha, form admirable illus- 

 trations. A short chapter on Pycnogonum and Nymphon 

 concludes this really wonderful volume. P. M. D. 



OUR BOOK SHELF 



Heat. By B. Loewy (Lardner's Handbook of Natural 

 Philosophy. Crosby Lockwood and Co., 1877.) 



This, though not a bulky book, is a sort of miniature 

 Encyclopeedia of the subject. So far as we have read it 

 it seems to have all the faults of the original (?) work to 

 which Lardner's name was prefixed, with the important 

 exception of the inaccuracies. These have been to a 

 great extent removed, and the work has been brought up 

 to date, but there is still the woeful want of order, or 

 indeed of any guiding principle whatever which distin- 

 guished the former editions. It is a very curious mixture 

 of good and bad, and cannot be called, in any sense, 

 attractive to the reader. Numerous tables of expe- 

 rimental data are given, but they are in many cases 

 carried to a number of places of figures quite beyond the 

 present power of experimental science. Two, or perhaps 

 three of tbe figures in the earlier places of each number 

 are probably correct ; the others give a show of minute 

 accuracy which may altogether deceive the beginner. The 

 treatment of the theoretical part is very meagre, but in 

 the experimental part many curious facts not usually 

 known are given. The book may be useful as a work of 

 reference to those who are not in possession of Balfour 

 Stewart's treatise, but we cannot say more in its favour. 



Ferns, British and Foreign. The History, Organography, 

 Classificatioti, a7id Enumeration of the Species 0/ Garden 

 Fertts, with a Treatise on their Cultivation. By John 

 Smith, A.L.S., Ex-Curator of the Royal Gardens, Kew. 

 New and Enlarged Edition. (London : Hardwicke 

 and Bogue, 1877.) 

 That Mr. Smith's " Ferns, British and Foreign " should 

 have reached a new edition in a comparatively short 

 time is no small tribute to its value as a book of reference 

 for amateurs and fern cultivators. The chief portion of 

 this very neatly got up work is occupied by an enumera- 

 tion of cultivated ferns. The different genera, as under- 

 stood by the author, who was one of the foremost pteri- 

 dologistsjof his day, are described and figured, while a list 

 of the cultivated forms, with synonyms and range of 

 geographical distribution, follow under each genus, no 

 attempt being made to give a diagnosis of the species. 

 The scope of the work is therefore entirely different from 

 that of the " Synopsis Fihcum " of Hooker and Baker. 

 The classification adopted is that propounded by Mr. 

 Smith in his early publication on ferns, an arrangement 

 not much used by modem writers. An appendix of 

 recently-introduced ferns is given. These have been col- 

 lected and arranged under their respective genera and 

 tribes, as their names have from time to time been 

 noticed in the horticultural journals and in nurserymen's 

 catalogues. The list has thus no pretensions to be a 

 critical one. The most interesting part of the book is the 

 history of the, introduction of exotic ferns, a subject about 

 which, probably, no man living knows more than Mr. 

 Smith. This is followed by an explanation of terms used 

 in describing ferns, perhaps the least satisfactory part of 

 the whole volume, as many of the terms are more or less 



obsolete, or only used in the book now before us. In this 

 section nothing is said about the recent researches into 

 the nature of the prothallus, construction of the reproduc- 

 tive organs, and morphological nature of the sporangia. 

 The last part of the work is occupied by an essay on the 

 cultivation of ferns, reprinted without alteration from the 

 first edition, but giving the results of long expeiience of 

 the successful cultivation of all groups of ferns. As a 

 work of reference and guide to the cultivation, this book 

 will most undoubtedly be of great service to the fern- 

 growing public. 



LETTERS TO THE EDITOR 



[The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undetiake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communications. 



The Editor urgently requests correspondents to keep their letters as 

 short as possible. The pressure on his space is so great that it 

 is impossible otherwise to ensure the appearance even of com- 

 munications containing interesting and novel facts.l 



The Radiometer and its Lessons 



I HAVE little doubt that Prof. Osborne Reynolds is much more 

 competent than I am to say what is or is not consistent with the 

 kinetic theory of gases, but I hardly think that he gives evidence 

 of this in his letter to last week's Nature (p. 27). Unless my 

 Ignorance of the matter is more complete than I am aware of, 

 the law that the rate of communication of heat to a gas is inde- 

 pendent of the density, applies only when the space occupied 

 by the gas is so great, or the variations of density so small, 

 that these variations do not alter the temperatures of those 

 portions of the gas which are at each instant respectively re- 

 ceiving and giving out heat. This condition cannot, I imagine, 

 be fulfilled in the radiometer, where it seems to me inevitable 

 that an action of the kind to which Mr. Johnstone Stoney 

 called attention must take place. G. Carey Foster 



P.S. — Since writing my previous letter to Nature, a fort- 

 night ago, I have read a paper by Mr. R. Finkener, in Foggen- 

 dorff^'s Annalen (vol. clviii. pp. S72-595). This paper contains, 

 besides a theoretical investigation of the motion of the radio- 

 meter founded oft the kinetic theory of gases, an experimental 

 proof that the action becomes much less when an extremely high 

 degree of rarefaction is reached. The paper itself is not dated, 

 but, as the Part of the Annalen which contains it was " closed " 

 on July 31, 1876, the experiments described in it cannot have 

 been much, if at all, subsequent to those (communicated to the 

 Rojal Society, June 13, 1876) which led Mr. Crookes to a like 

 result. G. C. F. 



Until I read Dr. Carpenter's letter in your issue of the 8th 

 inst., it had never occurred to me that his "special purpose" 

 was to bring out strongly my " thoroughly scientific and philo- 

 sophical method ! " This is an act of disinterested kindness 

 which recalls to me the exquisite truth ot Dean Swift's remark, 

 " No enemy can match a friend.' 



Dr. Carpenter's only reply to my letter which appeared in 

 your issue of the ist inst. is contained in the following passage : — 

 "If I had not found," he says, "after the publication of my 

 Lectures, that he had himself been 'digging up the hatchet,' which 

 I was quite disposed to keep buried, by giving his public 

 attestation to the ' spiritualistic ' genuineness of what had been 

 proved to be a most barefaced imposture, I should not have 

 again brought his name into the controversy." 



Further on Dr. Carpenter paraphrases passages from his article 

 in Eraser's Magazine for this month, in which he goes more into 

 detail touching this "public attestation," of which in his eyes I 



" Eva Fay," he says, "returned to the United States, carrying 

 with her a letter from Mr. Crookes, which set forth that since 

 doubts had been thrown on the Spiritualistic natvu'e of her 

 ' manifestations,' and since he in common with other Fellows of 

 the Royal Society had satisfied himself of their genuineness by 

 ' scientific tests,' he willingly gave her the benefit of his attesta- 

 tion. This letter was pubUshed in facsimile in American 

 newspapers." 



My answer to this calumny shall be brief. 



It is untrue that I dug up the hatcbet—Dr. Carpenters 



