Ulay 24, 1877] 



NA TURE 



61 



liarities of the principal plants in each order are briefly 

 described as well as their economic uses, together with 

 notes on the most general method of propagation. 



The book will no doubt meet with a wide circulation ; 

 the chapters on propagation, grafting, and budding, being 

 of a practical character, will be useful to other readers 

 besides those of a purely scientific turn. As a further 

 illustration of this we may point to the chapter on Seed- 

 saving, in which we are reminded of the excellence of the 

 produce of the Continental seed farms, especially those 

 of Erfurt, which are noted for their Primulas, Stocks, 

 Balsams, Asters, &c. ; we are also told that the seed of 

 such common plants as Cineraria and Calceolaria is, 

 when of a " good strain,-" worth from 10/. to 15/. per 

 ounce, and Primula serds even more. The book has a 

 good index, always a special point of value in one in- 

 tended for reference. 



LETTERS TO THE EDITOR 

 \Tlie Editor does not hold Inmsclf responsible for opinions expressed 

 by his eorrespondents. Neither can he undertake to return, 

 or to corrcipond with the writers of, rejected manusciipts. 

 No notice is taken of anonymous communuations. 

 The Editor urgently requests correspondents to keep their letters as 

 short as possible. The p-essure on his space is so great that it 

 is impossible otherwise to ensure the appearance even of com- 

 munications containing interesting and novel facts.'] 



The " Hibernation " of Birds 

 I TRUST your correspondent " X " will not object to my point- 

 ing out that the " hibernation " story which he retails in Natup,e 

 (vol. xvi., p. 43) has in common with dozens, not to say scores, of 

 others, the delect of being delivered at second-hand, without 

 even the slightly confirmatory evidence which the name of the 

 observer of the marvel and of the place where it occurred would 

 supply. As such it may surely be dismissed to the limbo of (I 

 will say) legends. That which has been furnished by the Duke 

 of Argyll (vol. xv., p. 52S) rests on a better base, and is almost 

 the first I have met with for which a respectable man vouches. 

 Far be it from me to deny the possibility of a miracle being 

 wrought in Persia, but I confess that without impugning Sir 

 John McNeill's veracitv, I simply refuse to believe the story 

 except I regard as miraculous the incident he relates. Now there 

 is a common supposition that miracles are only performed with 

 some worthy end in view, and, moreover, that unle.ss a miracle 

 is recognised as such by the witnesses thereto its effect is nullified. 

 This supposition may, however, be wrong, lor it is hard to con- 

 ceive what may have been the end of this miracle, and its super- 

 natural quality is clearly not acknowledged by the distinguished 

 persons present. One would find greater satisfaction, per- 

 haps, if the Duke of Argyll had expressed his belief in it, but 

 he contents himself with saying that he had " frequently heard" 

 his brother-in-law relate the circumstance. The identity of this 

 phrase with that said to have been used by another great man on 

 another occasion is vary striking, and since the story, though 

 old, is short, perhaps you will let me tell it. I have heard that 

 King George IV., some years before his death, was strongly 

 possessed with the notion that he had been present at the battle 

 of Waterloo. Once as he was recounting his personal adven- 

 tures on that eventful day, he perceived some uncourtly sign of 

 incredulity shown by one of his audience. Turning to the late 

 Duke of Wellington, who was of the company, he appealed to 

 him — "Isn't that true, Arthur?" The adroit reply was— " I 

 have irequently heard your Majesty say so." 

 May 19 The Reviewer of Palmiln's Work 



Barlow's and Laslett's Determination of the Elasticity 

 and Strength of Timber 



On comparing the results of Mr. Barlow's determination of 

 the modulus of elasticity of Teak timber, given in his " .Strength 

 cf Materials," p. 82, sixth edition, with the results of different 

 Uutch investigators on Djati timber of Java, I was struck by 

 the great dilfetence between those results, those of Mr. Barlow 

 being very much higher than the others, though leak of British 

 India and Javanese Djati are merely different names for the same 

 species, Tectona grandis, L., of the family VerbenaceiE. My 

 own experiments, which will, I hope, be afterwards published 



in my inaugural dissertation, show also the complete identity 

 between Teak and Djati. This led me to detect a serious error 

 m Mr. Barlow's calculations. He measures the deflection pro- 

 duced by a certain weight of a batten 7 feet by 2 inches square, 

 supported at both ends on two props, the bearing distance being 

 6 feet, as is stated on p. 67 in the general description of his 

 arrangements. The value of E is found in this case by the 

 formula — 



E=Jl2^ 

 l6ad'' 5 



in which / is the bearing distance ; in the case of Mr. Barlow, 

 equal to 6 feet. Now all Mr. Barlow's £ 's are calculated by 

 introducing / = 7 feet instead of / = 6 feet, as should be ; the 

 consequence is that all those values are too great. So for Teak 

 timber the value of £ is found to be = 603,600 lbs., while the 

 true value is £ = 380,023 lbs. on the square mch. Also in the 

 formula for the strength — 



€•_ i ''" 

 ^ 4adi 



I is the bearing distance, Mr. Barlow calculates .J = 2,462, 

 taking / = 7 feet, the real value being S = 2,1 10-5 for / - 

 6 feet. 



Mr. Thomas Laslett, in his "Timber and Timber-trees" 

 (London : Macmillan and Co., 1S75), following the arrange- 

 ments of Mr. Barlow, commits the same error. On p. 42 he tells 

 us that in all his experiments pieces were taken 2" x 2" x 84" = 

 336 cubic inches, and that each piece was placed upon supports 

 exactly 6 feet apart. But for / is taken, instead of the bearing 

 distance 6 feet, the whole length 7 feet. So all the numbers for 

 the moduli of elasticity of the different woods calculated by Mr. 

 Laslett are too great in the proportion j" : 6^, and the numbers 

 for the strength in the proportion 7 : 6. 



The reduced values for E from Mr. Laslett, namely, E = 

 362,870 and E = 305,876, and that from .Mr. Barlow, E = 

 380,023, agree tolerably well with the mean resuUs of Dutch 

 investigators, £ = 404,210, and much better than does tlie un- 

 corrected value, E = 555, iSo. Other determinations of the E 

 of Teak timber are not known to me. 



The results of Mr. Barlow were already published in the year 

 1S17. Since that time several editions of this valuable work have 

 appeared ; in the year 1S67 the sixth edition, revised by his two 

 sons. General Morin gives in his " Resistance des Materieux " 

 all the results of Mr. Barlow on timber, reduced to metric 

 weights and measures. Also MM. Chevandier and Wertheim, in 

 their " Memoire sur les Proprietes Mecaniques du Bois." It is 

 scarcely to be believed that none of these eminent men, nor any 

 one else, have remarked this error in the calculation of Mr. 

 Barlow's often used numbers. S. FiGEE 



Haarlem, Holland 



Basking Shark 



I THINK it but just to Prof Bocage to ask you to publish the 

 inclosed letter, which only reached me on the first of this month, 

 owing to its having been sent to a wrong address. I regret that 

 I overlooked Signor Capeilo's memoir on Selache maxima, which 

 was so plainly indicated in the Zoological Record for 1869. I 

 had, indeed, the " Catalogo dos peixes de Portugal que existem 

 no Museu de Lisboa, por F. de Brito CapeUo," which was pub- 

 lished in No. vi. of the Lisbon Journal of Science ; but No. vii., 

 which the author (whose kindnesses to me when at Lisbon, iii 

 186S, I cannot forget) sent to me, I never got, and hence one 

 cause of my oversight. E. Perceval Wright 



Trinity College, Dublin 



Lisbonne, le 14 fevrier, 1S77 



Monsieur et honor^ Confrere,— Dans I'article que vous 

 avez pubUe dans la Nature sur le " Basking Shark," vous aver, 

 comme le Professeur Paul Gervais et d'autres, attribue a i\L 

 Steenstrup la decouverte des appareils tamisants ou fanons 

 branchiaux du squale pelerin ou Sijualus maxtmus. Si vous 

 vous donnez la peine de consulter No. vii. du Journal des 

 Sciences Math., Phys. et Nat. de Liibonne, vous y trouverez a 

 p. 236, la description de cet appareil ; vous trouverez cgalement 

 ces appareils figures sur la planche qui accompagne cet article 

 et qui contient aussi la figure du poisson. La description et la 

 figure des appareils branchiaux ou des fanons branchiaux du 

 Si], maxtmus (et des especes congeneres) ont c-tc- done publics 

 par M. CapeUo, aide-naturaliste au Mu»eum de Lisbonne, en 

 aout de l!)69 ; c'est-a-dire 4 ans avant la pubhcation de I'article 



