Mar. 7, 1872] 



NATURE 



363 



calculation. The future must show how far it will be 

 possible to apply to the theory of species the definition 

 of central specific forms, from which varieties calculably 

 diminish in numbers as they depart in type. 



E. B. TvLOR 



OUR BOOK SHELF 



Magnetism. By Sir W. Snow Harris and H. M. Noad. 



(London : Lockwood and Co.) 

 This is a good book, and we are glad to see the subject 

 of magnetism fully treated in a popularly written te.Kt-book. 

 It is a second edition of Sir William Snow Harris's 

 rudimentary treatise, with considerable and important 

 .additions by the editor. The part of chief importance 

 which is added is Chapter viii., which deals with the more 

 recent progress of terrestrial megnetism. This chapter 

 consists of thirty pages, and the author has managed to 

 condense into that space a wonderfully large amount of 

 interesting, useful, and accurate information on the 

 subject. In so short a space we must be content with 

 results rather than with particulars, but the matter con- 

 tained in this chapter, in point of importance, accuracy, 

 and exhaustiveness, places the present treatise, as far as 

 terrestrial magnetism is concerned, much before any 

 similar book with which we are acquainted. The correc- 

 tion of the compass in iron ships is entered into in the last 

 ch.apter. The telegraph is scarcely touched upon, but 

 this perhaps rather belongs to a treatise on electricity. 

 We have a chapter on theories of terrestrial magnetism. 

 The theory of Gauss should never be classed, as it is here, 

 and indeed as it is generally classed, along with theories 

 like those of Halley or Hanstein, or with such things as 

 electro-magnetic theories and the like. The word " theory " 

 in these cases means quite a different thing from what it 

 means when applied to Gauss's investigations. Hanstein 

 and the like all make some physical hypothesis, which 

 may or may not be the case ; but Gauss makes no such 

 assumption at all, except in so far as he supposes that 

 the needle at all parts of the earth's surface is affected by 

 forces due to the same origin, and varying inversely as 

 the square of the distance, which has been experimentally 

 proved to be the law according to which magnetic forces 

 act. He then shows how the effect on a needle can be 

 expressed in terms of an infinite series which is neces- 

 sarily mathematically convergent and true, and he then 

 uses an approximation to that series, which approxima- 

 tion is justified fully by experiments similar to those made 

 by the late Prof Forbes at the top and bottom of the 

 Faulhorn. Gauss's theor)', then, is a truly scientific 

 theory, inasmuch as it involves no unjustified physical 

 hypothesis, but is a logical deduction from observed facts 

 and established principles, and in this dift'ers radically 

 from the other theories which are too often classed with 

 it. Dr. Noad has been so successful in Chapter viii. that 

 we cannot help wishing he had introduced a chapter also 

 on this subject. James Stuart 



The Amateur's Flower-Garden : a Handy Guide to the 

 Formation and Manat^ement of the Flower Garden 

 and the Cultivation of Garden Flowers. By Shirley 

 Hibberd. Illustrated with coloured plates and wood 

 engravings. (London : Groombridge and Son, 1871.) 



Mr. Hihiierd is a practised writer on gardening subjects, 

 though his books have not much claim to be considered 

 as scientific treatises, but rather as pretty gift-books to lie 

 on the drawing-room table and give to its furniture a 

 y?/(7j-/-scientific air. That they have their use cannot be 

 doubted, but it is not a very high one. The worst 

 part of this book is the illustrations. From the letter- 

 press may be doubtless culled some useful hints as 

 to the planting and management of a flower-garden, 



though we do not think it equal in this respect to some 

 other works, such as those by Mr. Robinson, which are 

 less under the trammels of time-honoured prejudices and 

 superstitions. But many of the illustrations, including 

 some of the woodcuts and nearly all the coloured plates, 

 are simply atrocious. The drawings of a show pelargo- 

 nium (p. 80), pansy (p. 45), ranunculus (p. 156), carnation 

 (p. 117), and some others, are mere caricatures, and un- 

 worthy of a place in any work which bears the least 

 pretensions to a scientific character. 



LETTERS TO THE EDITOR 



[ The Editor does not hold himself responsible for opinions expressed 

 l)y his correspondents. No notice is taken of anonymous 

 communications. ] 



The Survival of the Fittest 



I HAD designed sending a note to you, critical of the abstract 

 of my paper on "The Laws of Organic Development," repub- 

 lished froai the American Naiuralistm one of your recent issaes, 

 before I read the remarks of Mr. Spencer in your number of 

 February i. 



If Mr. Spencer will examine the Essay itself (for sale by 

 McCalla and Stavely, 237, Dock Street, Phila., or Naturalists' 

 Book Agency, Salem, Mass.*) he will find that I h.ave there ex- 

 clusively employed his phrase " Survival of the Fittest." The 

 expression "Preservation of the Fittest," not used by Mr. 

 Spencer, was inadvertently introduced in writing the ab3tra;t. 

 This was done hurriedly between the sittings of the Amer. Assoc. 

 Adv. Sci. for a reporter of the Neio Yor/; TribiDu; and was sub- 

 sequently printed by the Naturalist while I was absent on the 

 Plains of Kansas. It therefore contains several obscurities, the 

 result of an attempt to abridge, and a number of typographical 

 blunders. The essay will be found to be free from these. 



There being no misrepresentation of Mr. Spencer's views on 

 this point, I notice the second objection he makes. Where, in 

 the sentence regarding the Survival of the Fittest, I say that 

 "this neat expression no doubt covers the case, but it leaves 

 the origin of the fittest entirely untouched," Mr. Spencer regards 

 my language as an " indirect statement that I " (Mr. S.) " have 

 done nothing to explain the origin of the fittest." 



It is plain enough that my remark does not apply to Mr. 

 Spencer or to his writings, but exclusively to the doctrine of 

 Natural Selection, and to Mr. Spencer's terse phrase, "which 

 no doubt covers the case," i.e. Natural Selection (not the whole 

 theory of Evolution). I cannot see that this language can be 

 tortured into the interpretration Mr. Spencer places upon it, but 

 Mr. Spencer's language decidedly implies that my statement is 

 literally correct. 



I am, however, well aware that Mr. Spencer has done more 

 than any living man to explain the " Origin of the Fittest," and 

 on this account in particular his name does not appear in my 

 criticism. Another reason for its omission is that I have taken 

 the liberty not to read his work, " The Principles of Biology," 

 because I have suspected, from my reading of other works of this 

 philosopher, that it is in advance of other treatises on the subject. 

 I postponed it until, by investigation "in the shop," I should 

 have attained to some definite views based on reasoning un- 

 influenced by the opinions of others, hoping to use "The 

 Principles of Biology " thereafter in such a way as its merits 

 and justice to its author should require. 



Edward D. Cope 



PhUadelphia, Feb. 20 



Ethnology and Spiritualism 



There is only one point in Mr. Tylor's communication 

 (Nature, Feb. 29, p. 343) on which it seems desirable that I 

 should say a few words, in order that I may not be supposed to 

 assent to what I conceive to be a most erroneous view. Mr. 

 Tylor suggests that the phenomena that occur in the presence of 

 what are called mediums, are or may be of the same nature as 

 the subjective impressions of persons under the influence of a 

 powerful mesmeriser. Five and twenty years ago I was myself 



* Under the title, " The Method of Creation of Organic Types." 



