344 



NA TURE 



[August 9, 1883 



laid on wet cloth are beginning to give distinct evidence of the 

 production of cups. The probability at present is that S. varium 

 is the Sclerotium of a Peziza, nearly allied to Peziza tuberosa. 



A. Stephen Wilson 



North Kinmundy, Aberdeen, July 30 



p.S. — Since the above was written I have discovered amongst 

 growing potatoes great numbers of S. varium with the completed 

 fungus attached to them. It is a yellowish-brown Peziza of 

 various diameters up to half an inch. I send you a box of 

 specimens. — A. S. W. 



"Zoology at the Fisheries Exhibition" 



In Nature, vo'. xxviii. p, 2S9, is an article upon the zoology 

 of the Fisheries Exhibition, in which the writer states that some 

 of the corals exhibited by Lady Brassey belong to me and are 

 not that lady's property. Will you permit me to emphatically 

 assert that not a single coral in the case belongs or ever did 

 belong to myself, and that every specimen was procured by Lady 

 Brasiey during her voyages in the Sunbeam. 



What is meant by the words "gratuitous inventions" I can- 

 not understand ; the new species were carefully compared with 

 those in the British Mu:, -~i, also with those obtained during 

 the Challenger expedition, ...... ivith the works of Lamarck, Dana, 



Milne-Edwards, Moseley, and others. 



It is possible that the commissionaire in charge may have, in 

 dusting the collection, shifted some of the labels, but the fact 

 remains that Lady Brassey'? collection of corals is the only one 

 in the Exhibition which gives any information either upon the 

 nomenclature or habitat of the specimens exhibited. 



204, Regent Street, W., August 4 Bryce-Wright 



"The Student's Mechanics" 

 I have no wish to quarrel with the review you have printed 

 of my book, " The Student's Mechanics ; " and I have to thank 

 the reviewer for drawing attention to one omi-sion, namely, the 

 •failure to explain fully tne second law of motion, as related to 

 the two methods of measuring force. But I should be glad to 

 be allowed a few words to explain my treatment of Accelerating 

 and Moving force. One of my objects was to clear away, by full 

 explanation, the confusion which no doubt sometimes exists as to 

 those terms; and this I could not have done if I had omitted 

 them altogether. It will be long before a reader of works on 

 mechanics can safely remain ignorant of their meaning ; and 

 indeed the discu-sions of force as causing change of velocity 

 simply (as in kinematics), and as causing change of momentum, 

 are still kept so much apart that terms to indicate the distinction 

 do not seem out of place. Nor do I see any confusion likely to 

 arise between "acceleration" and " accelerating force " : the one 

 is the actual change of velocity in a given time, the other is the 

 force which causes that change. The latter is measured by the 

 former, but it is not the same thing. In Art. 422 the word 

 "accelerating" is simply used in opposition to "retarding," in 

 the sense of that which increases velocity instead of diminishing 

 it : I know no other word in use for the same purpose. Lastly, 

 the proof iu Art. 359 was given precisely to supply the omission 

 to which your reviewer calls attention, and which does exist in 

 the ordinary proofs that no velocity is lost in passing round a 

 smooth curve. I there show that the sum of such losses, in a 

 given time, is indefinitely small compared with the sum of another 

 set of quantities, which sum is itself finite ; hence the first sum 

 may properly be neglected. Walter R. Browne 



Sand 



As explained in my note on p. 245, I had not the advantage 

 of perusing Mr. Waller's paper on "Sand." Mr. Gardner, in 

 his notice of it gave the first place to "distinguishing with 

 certainty by the aid of the microscope sand that has been worn 

 by the action of wind from ?and that has been for long exposed 

 to surf, and this again from sand brought down from torrents." 

 I assumed this was its primary object. In this I am in error. 

 Mr. Waller says his " paper was to show that chalk flints had 

 scarcely any place in the formation of sand." Had I known 

 this was the purpose of his writing I would not have troubled 

 you with any remarks, as I entirely agree with Mr. Gardner 

 when he says, as in p. 225 : " The coast-line occupied by flint 

 shingle is almost limited to portions of Western Europe, and is 

 relatively insignificant." 



I am glad to learn that Mr. Waller has a more comprehensive 



object in view, and that a large series of sands from modern and 

 ancient formations are being examined microscopically, and 

 shall be glad to supply portions of specimens of the soils and 

 subsoils of Australia and New Zealand which contain sand, and 

 were examined under the microscope ten years ago, to compare 

 their form and appearance with similarly situated soils from 

 Europe. James Melvin 



Treble Primary Rainbow 



On Sunday, luly 15, as a heavy thunderstorm was passing 

 away from over'this place, a brilliant rainbow appeared a little 

 to the south of east about 5.45 p.m. There was a complete 

 primary arch and a nearly perfect secondary one, and on being 

 led to examine the former in consequence of its appearing un- 

 usually br^.ad, it appeared to be made up of three bows, one 

 directly below the other. The red of the spectrum being re- 

 peated three times was what drew my attention to this point. 

 The two lower bows appeared smaller than the top primary arch. 

 Thinking I must be suffering from some optical illusion, I got 

 my wife, brother, and my little girl of nine, all to look carefully 

 at the rainbow, and found that they all saw three distinct bows 

 in the primary arch, in addition to the secondary arch. Is not 

 this an unit ual occurrence ? *•• 



Bexley, Kent, July 21 



[This is merely the veil-known phenomenon called spurious 

 bows, which has not yet found its way into the " popular " class of 

 text books, though the principles of its explanation were long ago 

 pointed out by Young. The full theory was given by Airy, and 

 found to coincide with the very exact measurements of Hallowes 

 Miller. When the raindrops are all of the same size, each 

 wave-length in the rainbow has one principal m urimum with an 

 infinite number of subsidiary maxima of rapidly-decreasing 

 brightness. These lie inside the chief maximum in the primary 

 rainbow, and outside it in the secondary. — Ed.] 



FUEGIAN ETHNOLOGY 

 T N Guido Cora's Cosmos for May, 1883, Lieut. Bove, of 

 *■ the Italian Antarctic Expedition, supplies some inter- 

 esting details on the little known inhabitants of Tierra del 

 Fuego, amongst whom he spent some time in the spring 

 of the present year. He speaks highly of the English 

 missionaries stationed at Ushiwaya, in Beagle Channel, 

 who have succeeded in introducing a few rudimentary 

 notions of human culture amongst several tribes hitherto 

 supposed to be quite irreclaimable. As had long been 

 suspected, the archipelago is found to be occupied not by 

 one but by three distinct races, the Alacalufs in the west, 

 the Onas in the east, and the Yagans in the south. Of 

 these the Yagans, who stretch from the north side of 

 Beagle Channel southwards to Cape Horn, appear to be 

 the true aborigines. They have been driven to the 

 southernmost and most inhospitable islands by the Onas 

 and Alacalufs, both intruding from the mainland. The 

 Onas, who are clearly of Tehuelche origin, penetrated 

 from Patagonia across the eastern arm of Magellan 

 Strait, into the large island of King Charles South Land 

 (Eastern Tierra del Fuego), which they now hold almost 

 exclusively. In the same way the Alacalufs, of Arau- 

 canian stock, made their way from the Chilian Andes, 

 across the western arm of Magellan Strait, into the 

 western islands, which they now occupy from Cape Pillar 

 to Stewart Island,at the Pacific entrance of Beagle Channel. 

 They number scarcely more than 2000 altogether, while 

 the Yagans and Alacalufs are estimated by the English 

 missionaries at about 3000 each, giving 8000 for the 

 whole archipelago. 



Although now representing the most aboriginal element, 

 the Yagans themselves would appear to belong originally 

 to the same Chilian family as the Alacalufs, the points of 

 difference being easily explained by their longer isolation 

 from the parent stock and by the more unfavourable 

 climatic conditions of their present homes. From nu- 

 merous measurements taken by Bove, they seem to be 

 much below the middle height, although still nearly as 

 tall as the Araucanians of the mainland. Of these the 



