!66 



NA TURE 



[August i8, 1904 



ActuaUUs scioUifiques. By Max de Nansouty. Pp. 



329. (Paris : Schleicher Fr^res et Cie., 1904.) Price 



3.50 francs. 

 This collection of short popular essays on scientific 

 subjects is likely to appeal to a wide circle of readers. 

 The questions selected for treatment are those pertain- 

 ing- to recent discoveries which have been given 

 prominence in the Press. To name a few of the titles 

 is enough to show the character of the book, especially 

 when it is added that a subject is rarely given more 

 than four pages by way of explanation :— -Radium and 

 radio-activity, wireless telegraphy, captive balloons, 

 electric cookery, and so on. The book may prove of 

 service in this country to young people fond of science 

 who are learning French. 



LETTERS TO THE EDITOR. 

 {The Editor does tiot hold himself responsible for opiniom 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 tnantiscripls intended for this or any other part of Nature 

 No notice is taken ol ijnon\nini,> . .nmininicalwns.] 



An Optical Phenomenon. 



A SHORT time ago, when experimenting with a cubical 

 mirror, I noticed the following peculiar phenomenon :— 



Diffused daylight from a near window fell on the mirror, 

 and was reflected towards the observer. Now, the mirror 

 was made to revolve slowly. A succession of Hashes of 

 white light was thrown at the observer as the different 

 faces passed before the eye. When the rate of about two 

 revolutions per second was reached, instead of the white 

 flashes, a displav of various colours, resembling interfer- 

 ence colours, was observed, and this effect continued until 

 about six revolutions per second were made, when the 

 colours disappeared, and a uniform grey light was 

 reflected. The experiment was repeatedly made, and always 

 with the same effect. 



The exact moment of appearance and disappearance of the 

 colour effect could only be determined approximately, nor 

 is there, apparently, a definite order in which the colours 

 succeed each other. At least, I was unable to distinguish 

 a strict order, but this may have been due to the imperfect 

 way of turning the mirror, viz., by hand power, means of 

 obtaining an absolutely uniform rate not being available. 

 As a rule, several colours appear at the same time, one 

 near the other. On the whole, however, it may be said 

 that green tints predominate, whilst yellow hardly appears. 

 Bluish tints seem to predominate at the beginning and 

 towards the end of the colour range. 



The experiment may also be varied in the following 

 manner : — Place the mirror so that the direct sunlight 

 strikes it. Then turning the mirror, observe the path of 

 reflected light on the wall. In this path, not far from the 

 mirror, fasten a piece of white paper to the wall. When 

 the mirror is then turned at the above-named rate, the 

 colours will be seen on the paper. 



To secure a quick perception of the colours, it is well, 

 in both cases, to start with a high speed of rotation, and 

 then to slacken it gradually. 



I would like to know whether this phenomenon has 

 already been observed by others, and also how it may be 

 explained. Fred J. Hillig. 



St. John's College, Toledo, Ohio, U.S.A. 



The Celtic Pony. 



At a sale of Icelandic and Welsh ponies held at Gates- 

 head on July 14, I observed a small black Welsh stallion 

 which had the essential characteristics of the Celtic pony 

 (Equus caballns celtict4s) lately described by Prof. Ewart. 

 There was no trace of a callosity on either hind leg, and 

 the tail had a very well marked caudal fringe or tail-loclv, 

 while in most other respects this pony conformed to the 

 Celtic type. I believe that this is the first instance on 

 record of a Welsh pony resembling the Celtic variety in 



NO. 1816, VOL. 70] 



all the main points. The other Welsh ponies at the sale, 

 so far as I noticed, possessed hock callosities, but the 

 majority of these resembled the Celtic pony in having a 

 more or less distinct caudal fringe. 



The occurrence of " Celtic " characters in Welsh and 

 other ponies which usually differ from E. caballus celticus, 

 as pointed out by Mr. Annandale and myself in a paper on 

 Fjeroe and Icelandic ponies (Proc. Camb. Phil. Soc, vol. 

 .xii., 1904), is in no way inconsistent with the view we put 

 forward that the present distribution of the Celtic pony 

 is related to the Viking migration. This view receives con- 

 firmation in Dr. Stejneger's statement that there is a 

 Norwegian breed called the " fjordhest " which is closely 

 allied to if not identical with the Celtic pony. But though 

 the purest representatives of the Celtic pony at the present 

 day seem to be generally restricted to certain (usually 

 isolated) parts of north-west Europe, it would appear that 

 there are traces elsewhere of the primitive small-headed- 

 horse (the probable ancestor of the Celtic pony, according 

 to Prof. Ewart) which had a wider distribution. The Welsh 

 and other ponies which sometimes show Cehic characters, 

 as well as certain of the smaller Arabs, probably represent 

 such traces (see Ewart, "The Multiple Origin of Horses 

 and Ponies," Trans. Highland and Agric. Society of Scot- 

 land, 1904). 



Out of sixty Icelandic ponies which I examined at the 

 Gateshead sale, I found fourteen without hock callosities, 

 a rather unusually high proportion. .Ml colours were re- 

 presented, but the commonest and probably the most typical 

 colour with the Icelandic ponies was light dun with a dark 

 line down the centre of the back. 



Francis H. .\. Marshall. 



Monksfield, Freshwater Bay, Isle of Wight, August lo. 



THE NEEDS OF ANTHROPOLOGY AT 

 CAMBRIDGE. 

 A T first sight it does not strike one as a particularly 

 ■*»■ edifying spectacle to see an appeal for funds 

 made by a department of an ancient university, but 

 after all it is a hopeful sign, as it indicates normal 

 expansion or growth along new lines. It is a common 

 mistake to regard the Universities of Oxford and 

 Cambridge as well endowed; the wealth, such as it is 

 — or rather such as it was — belongs to the colleges 

 and not to the university, and as these universities 

 are not endowed with public funds, they have to rely 

 solely upon ancient and recent benefactions in addition 

 to fees received from students. Consequently, when 

 old subjects -expand rapidly, or new subjects arise, 

 there are insufficient funds to meet their needs ; 

 especially is this the case for scientific subjects, as, in 

 addition to the lecturers, class-rooms, and books of 

 the older subjects, these require demonstrators, labor- 

 atories, apparatus, and specimens. Museums, which 

 are a necessity to many branches of science, are ex- 

 pensive institutions to erect, maintain, and increase. 

 They are a relatively new feature vn university educa- 

 tion, and, though they are at present regarded by some 

 with suspicion and by more with dismay, they are 

 essential alike to teaching and research, and it is safe 

 to predict that their value will become increasingly 

 recognised. The chief reasons why museums are so 

 generally misunderstood are because they are too small 

 or too badly constructed to display their contents ; they 

 are understaffed and starved in funds for cases and 

 additions, and, finally, they are not properly arranged. 

 The last count is very largely dependent upon the 

 previous conditions, for only those who have had ex- 

 perience can fully realise the impossibility of orderly 

 and educative installation when every department 

 of the museum is overcrowded and new specimens or 

 collections are continually coming in. It is usuallv 

 extremely difficult for a curator to keep pace with the 

 new material in addition to the ordinary routine work 

 of a museum, and as scarcely any museum has any- 



