io4 



NA TURE 



[May 31, 1888 



inextricably entangled in the medley of new systems made by 

 Continental workers, all of which systems differ the one from 

 the other as " chalk from cheese." It is a mere whi;n to imagine 

 that chapters on "The Anatomy of a Snail " and " The Anatomy 

 of a Fresh-water Mussel " should have been excluded since the 

 basis of systematic zoology is anatomy. And it is a mere whim 

 to cavil at the inclusion of the vars. minor, maxim 1, and " albida," 

 (exalbida, if you please, Mr. Reviewer, for so was it named by 

 Menke), and the monstrosity sinistrorsttm of Helix aspersa, since 

 Dr. Gwyn Jeffreys and Moquin-Tandon have named varieties and 

 used variety-names, and since Prof. E. von Martens, than whom 

 no better conchologist, expressly mentions that "it is certainly 

 desirable that every local form, well-marked zoologically or 

 geographically, should have a distinct name. " And may I turn 

 a reviewer on my own book, and ask myself how it is that I did 

 not, as your reviewer desires, give the localities for every 

 species, and make the book costly, and, by so doing, take 

 it away from the reach of the poorer classes ? Why also did I 

 not give the definite localities for-the now local species, when I 

 considered rightly that some of them may turn up in other, and, 

 perhaps, far distant spots to those now known ? In conclusion, 

 I would point out to your reviewer — for I must not occupy your 

 valuable space to any greater extent — that as there is a virtue in 

 the every-day affairs of this our mundane life which, to quote 

 Seneca, is " the only immortal thing that belongs to mortality," 

 so, as certainly, is there a virtue in right reviewing which is quite 

 as exacting and quite as important to always bear in one's 

 remembrance. J. W. Williams. 



51 Park Village East, N.W. 



In reviewing Dr. Williams's little book, I wished not merely 

 to point out the author's mistakes, but to guard young concho- 

 logists, to whom the book is addressed, from placing too great 

 reliance on the statements it contains. 



I felt also convinced that the author was not practically con- 

 versant with his subject ; indeed, that his knowledge was purely 

 derivative, and this the foregoing letter fully confirms. 



I will not occupy space with a detailed criticism on the author's 

 method of compilation, but will simply refer to a single instance, 

 quoted to show his want of care in referring to the original 

 sources of information, so needful in such a task. The method 

 of numeration of the tooth-formula, referred to by me as incorrect 

 at p. 7 of the "Hand-book," is now justified by the author, 

 who quotes Woodward as his authority ; but upon referring 

 to my brother's "Manual" I find that my statement was 

 fully justified by the fact that the quotation is not correct, 

 it having been taken by Dr. Williams from Prof. Jeffrey Bell's 

 "Comparative Anatomy," where my brother's name is given as 

 the authority for the instances quoted, and not for the whole 

 paragraph to which it is appended, and which does not appear 

 in his book. To the second part of Dr. Williams's whimsical 

 letter I feel sure it is needless to reply. 



Henry Woodward. 



129 Beaufort Street, S.W., May 28. 



Freaks of Nature. 



I INCLOSE a letter from my grandson Charles, a boy, son of 

 St. Vincent Erskine, the explorer, with whose travels you are 

 probably acquainted. 



This singular instance of a change in the habits of birds, 

 consequent on the advance of civilization, is extremely important 

 and interesting, as it evinces almost reasoning powers and 

 adaptation of habits to circumstances. As you are aware, some 

 birds in South Africa build their nests on the pendant boughs 

 of willow-trees as a defence against snakes and iguanas. 



These willows, like other trees in Natal, are rapidly becoming 

 scarcer, as they are cut down, whilst the bo/s who take the nests 

 increase. This is, no doubt, the cause of the birds changing 

 their nests to the telegraph-wires, where they are also safer from 

 their natural enemies. 



It would be interesting to know whether similar instances 

 occur elsewhere. D. Erskine. 



47 Gratton Road, Kensington, May 25. 



P.S. — It is remarkable also that the hole is at the side instead 

 of the bottom, showing that the bird was aware that the situation 

 was snake -proof. Darwin would have been glad of this proof 

 of evolution. 



While watching the landscape of Natal between Ladysmith 

 and Pietermaritzburg .from a Natal Government Railway 

 carriage, I saw some nests of the " golden weaver " bird. There 

 were four of them hanging in a row, close together. They were 

 the round kind, without the long arm. On one of the nests sat 

 a cock weaver bird, but I saw no hens. 



The nests seemed to be one or two years old, except one, 

 which was greener than the others, and most certainly one of 

 this season's. The chief peculiarity seemed to lie in the fact 

 that the birds had woven grass round the wire for some six or 

 eight inches, and two or three inches in circumference, before 

 beginning to make the nest, and that the bird had to deal with 

 a horizontal wire instead of a vertical stick or a branch. The 

 bird always twists the grass round the branch (if he builds on a 

 vertical twig) for some way up among the leaves and stalks, 

 leaving the long ends free, thus forming his foundation. Weavers 

 prefer to build on trees where the long slender twigs droop to- 

 wards the ground, and so afford a nice vertical slender support. 

 They are especially fond of the weeping-willow, whose slender 

 switches generally branch off into two small shoots at the end : 

 between these the bird loves to build his nest. Besides, the 

 willow has lots of leaves very near together, and so holds the 

 straws very well. On the wire he had no such support, but had 

 to trust to his own ingenuity to overcome the novel situation, 

 which task he seems to have accomplished very well. 



The entrance to these nests was not at the bottom, as usual, 

 but by a hole in the side, and all the nests did not look the same 

 way. 



I suppose there was only one nest a season or two ago, with 

 a single pair of birds ; soon we shall have a long string, or 

 rather wire, of these ingeniously built homes with their happy 

 quarrelsome occupants, making enough noise to stop all the 

 messages ever sent that way. They will hear all the " Govern- 

 ment" secrets : then we will be able to say truly, " A little bird 

 told me." C. H. Erskine, 



WHIRLWINDS, WATERSPOUTS, STORMS, 

 AND ROTATING SPHERES. 1 



IT is often necessary, in many branches of science, to 

 halt in our steady progress along the beaten roads of 

 induction, and say, " Fiat experimentum." We may not 

 always be able by this means to reproduce exactly all the 

 physical conditions of the phenomenon, we are investigat- 

 ing, or to evolve a test crucial enough to enable us to decide 

 between rival hypotheses. Nevertheless, the power we 

 thus gain, especially in the case of an atmospheric pheno- 

 menon, of seeing the entire system of action in a coup 

 a" ceil, of gauging its relative proportions, and of examining 

 its dependence and effects on its entourage, can hardly be 

 over-rated. 



Such would appear to have been M. Weyher's object 

 in the delicate and ingenious experiments which he has 

 so skilfully elaborated and described in the pamphlet of 

 91 pages before us. 



The physical theory of atmospheric eddies, including the 

 rotating flat dis'c or cyclone, and the rotating column 

 which manifests itself as a tornado, waterspout, or dust- 

 whirl, according to variations in its intensity and surround- 

 ing circumstances, has lately been developed to an extent 

 not generally known, principally by Ferrel, Sprung, Ober- 

 beck, and Marchi. It is therefore decidedly satisfactory 

 to those who believe in the progress of meteorology by 

 rational theory and deduction, to find that the motions 

 exhibited in M. Weyher's experiments, in which the con- 

 ditions in Nature are very fairly imitated, agree in every 

 point with those which have been deduced from their 

 physical theory. 



Theory, for example, shows that a tornado is due 

 primarily to an unstable condition of saturated air, ac- 

 companied by a gyrating motion (which may initially be 

 very small, and which is practically always present to 



, « " Sur les Tourb lions, Trombes, Tempetes, et Spheres Tournantes ; 

 Etude et Experiences." Par C. L. Weyher. (Paris, 1887.) 



