568 



NATURE 



[October 9, 1890 



Zoological Society of London for February of the present year, 

 and is entitled "A Synopsis of the Genera of the Family 

 SoricidcE." Probably the most extensive collection of these in- 

 teresting little mammals ever examined by a single investigator, 

 came under the hand of the writer of the wrorks just quoted, 

 wherefrom to make his deductions. His classification is most 

 complete and acceptable, and goes to show that the Shrews 

 are first to be divided into two sub-families, viz. the Soricidce, 

 and the Crocidurina:, the first being characterized by having 

 their teeth red-tipped, while in the latter the teeth are white. 

 Five genera make up the first sub-family — which stand, Sorex, 

 Soriculus, Blarina, Notiosorex, and Crossopus, In the Croci- 

 durina we find six genera — namely, Myosorex, Crocidura, 

 Diploinesodon, Anurosorex, Chimarrogale, and JSIectogale. This 

 adds four genera to M. Milne-Edwards's list, and from the same 

 omits the genus Neosorex. Dr. Dobson believes that " the red- 

 toothed Shrews diverged from the white-toothed, development 

 having proceeded on somewhat similar lines in the descendants 

 of both according to similarity of environment and modes of 

 life." Of Dr. Merriam's genus and type, Atophyrax bendirii, he 

 says that " there are no leading characters which would enable 

 one to define the genus, were I inclined to admit it in my 

 synopsis." 



It is refreshing in these days to meet with such classification, 

 and such an able classifier — one who, as Dr. Dobson most 

 emphatically does, draws good strong lines in taxonomy, and 

 discourages the hair-splitting methods adopted by some 

 mammalogists in these days. R. W. Shufeldt. 



Takoma Park, D.C, September 13. 



Musical Sands. 



In reference to the note respecting Mr. Hyndman's query 

 re sonorous sand (Nature, October 2, p. 554) it may be 

 interesting to him, and others, to know that in our own islands 

 musical sand is by no means rare. In the second edition of my 

 "Musical Sand," shortly to be issued, I shall give a list of 

 the places at which it occurs in England, Scotland, Ireland, and 

 Wales, showing that only observers are rare — not the sands. 



My investigations since my paper was first published nearly 

 two years ago have brought many new and interesting facts 

 under my notice, not the least being that the musical sands at 

 Studland Bay are always mute during an easterly wind. This 

 I have been able to account for. 



About three years ago I propounded a theory to account for 

 the emission of these musical sounds from sands ; briefly it is 

 that they are the result of the rubbing together of millions of 

 clean sand-grains very uniform in size : two such grains rubbing 

 together would not produce vibrations audible to us, but the 

 accumulation of such vibrations issuing from millions of surfaces, 

 and, approximately, of equal length, would produce a note 

 sufficiently powerful to be sensible to us. 



This theory has long been published, and though it has been 

 examined by some of our most eminent physicists, and tested in 

 a variety of ways since, nothing has been suggested which has 

 caused me to abandon it. I shall be pleased to send Mr. 

 Hyndman a copy of my first paper on the subject. 



Bournemouth, October 6. Cecil Carus-Wilson. 



With what Four Weights (and a Pair of Scales) can 

 be Weighed any Number of Pounds from i to 40 

 inclusive ? 



With two weights four amounts can be weighed, viz. each 

 weight and the sum and difference of the two. 



With a third, in addition to these four, the sum and difference 

 of each and the third can be weighed. Three weights therefore 

 give 13 amounts. Similarly a fourth weight gives 13 -f 2 x 13 -M, 

 or 40 amounts, exactly. 



It is therefore evident that each amount must be arrived at by 

 only one combination, and that the sum of the weights must be 

 40 pounds. To weigh 39 pounds, then, we shall clearly want a 

 I pound weight. With i and 39 we can weigh i, 38, 39, 40. 

 For the next weight 2 clearly will not do, as I could be arrived 

 at in two ways. Taking 3, we find that i, 3, and 36 give us 

 I, 2, 3, 4, 32, 33, 34, 35, 36, 37, 38, 39, 40. Now to get 5 

 without getting any amount by more than one combination we 

 clearly want 9, and this will be found to solve the question, the 

 weights being i, 3, 3^, 3^. A fifth weight of 3* will enable us 

 to weigh any number of pounds up to 121, and so on. 



E. R. F. 



Protective Coloration of Eggs. 



In view of Mr. Grensted's letter to Nature last year (vol. 

 xli. p. S3), asserting the writer's belief that the egg of the red- 

 backed shrike varies with the tint of the lining material of 

 the nest, and of my own reply to this (same volume, pp. 

 129-30), I had intended this summer to examine as large a 

 series of nests and eggs as possible, in order to verify or dis- 

 prove my former observations. I have, however, been unable to 

 devote any time to the matter; and have only obtained two 

 nests — both from the neighbourhood of Evesham. In each of 

 these, I must confess that Mr. Grensted's contention is borne 

 out. The lining of one nest is dull brown in colour; and the 

 eggs (5) are of a niouldy-brown ground-colour, tending towards 

 dull green. The lining of the second is brighter in tone ; and 

 contains a small fragment of red flannel. The eggs (5) of this 

 nest show the commoner flesh-coloured ground. 



In spite of these two instances, I must hold to my former 

 opinion, that the correlation of ground-colour and environment 

 is very imperfect in the nests and eggs of these birds. Next 

 year I hope to be able to examine a greater number of nests. 



E. B, TiTCHENER. 



Mote House, Mote Road, Maidstone, October 2. 



NO. 1093, "^'OL. 42] 



LUNAR PHOTOGRAPHY. 



THE idea of employing the process invented by 

 Daguerre and Nidpce for the purpose of obtaining 

 photographs of our satellite was first suggested by 

 Arago in a report made to the Paris Academy of Sciences 

 on August 19, 1839. Daguerre acted on the suggestion, 

 but, in spite of a long exposure, he obtained only feeble 

 impressions, in which all details were conspicuously 

 absent (Arago, " CEuvres," vol. vii. p. 458). The first 

 photographic representations of the moon may therefore 

 truly be said to have been made by Dr. J. W. Draper in 

 America by means of a Newtonian reflector of five inches 

 aperture. The specimens were presented to the New 

 York Lyceum of Natural History. The following is an 

 extract from the minutes of that association : 



"March 23, 1840. Dr. Draper announced that he had 

 succeeded in getting a representation of the moon's 

 surface by the daguerreotype. . . . The time occupied 

 was 20 minutes, and the size of the figure about i inch in 

 diameter." 



Dr. Draper also wrote in September of the same 

 year : — 



" There is no difftculty in procuring impressions of the 

 moon by the daguerreotype beyond that which arises 

 from her motion. By the aid of a lens and a heliostat, I 

 caused the moon-beams to converge upon a plate, the 

 lens being three inches in diameter. In half an hour a 

 very strong impression was obtained. With another 

 arrangement of lenses I obtained a stain nearly an inch 

 in diameter of the general figure of the moon, in which 

 the places of the dark spots might be indistinctly traced " 

 {Phil. Mag., vol. xvii. p. 222, 1840). 



In 1850, W. C. Bond, in conjunction with J. A.Whipple, 

 a photographer of Boston, obtained some really good 

 daguerreotypes of the moon. The instrument used was 

 the equatorial of 15 inches aperture belonging to Harvard 

 College Observatory, and images from two to three inches 

 in diameter were obtained on plates adjusted at its focus. 

 Some of these pictures on glass, and mounted for the 

 stereoscope, were exhibited in London at the Great Ex- 

 hibition of 1851, and also at Paris ("Annals, Observatory 

 of Harvard College," vol. i. p. clvii.). 



Also in 1850, Nidpce de St. Victor obtained a strong 

 impression of the full moon in twenty seconds on an 

 albumenized glass plate sensitized with silver chloride. 

 He had only discovered this photographic process a few 

 months previously, and the plate was exposed in order to 

 test the efficiency of the film employed. No attempt was 

 made, however, to follow the moon's motion, so the 

 pictured disk could hardly have exhibited the circular 



