4o8 



NATURE 



[July 13, 1916 



similarity in the mononuclear corpuscles. Platelets 

 were recognised in mammalia only. 



Valuable reports on sponges (calcareous and non- 

 calcareous) from the Indian Ocean have lately been 

 published by Prof. A. Dendy in the " Report to the 

 Government of Baroda on the Marine Zoology of 

 Okhamandal, in Kattiawar " (part ii., pp. 79-146, 

 10 plates). The specimens described were collected 

 by Mr. J. Hornell in 1905-6. Many of the calcareous 

 species are identical with those from the African 

 coast, while a large proportion of the Tetraxonida 

 and Ceratosa were already known from the seas 

 around Ceylon. The plates show the general aspect 

 and the spicules of the new species; unfortunately, 

 the material was largely unsuitable for histological 

 study, and it is to be hoped that collectors will take 

 to heart Prof. Dendy 's exhortation to avoid formalin 

 as a preservative for sponges. 



In the recently issued part. No. 4, of vol. v. of the 

 Transactions of the Royal Society of South Africa 

 Mr. F. Eyles contributes a long list of plants 

 collected in southern Rhodesia. His record, which 

 occupies 251 pages and is furnished with a full index, 

 includes representatives of 160 families, 869 genera, 

 and 2397 species. The plants collected are mainly 

 flowering plants and ferns, and details of localities, 

 collectors' names, and numbers are given for each 

 species. The record will prove of value to students 

 of African botany, and especially to those of the 

 Rhodesian flora ; it should also serve to encourage 

 others to collect and study the plants of the country. 



A STUDY of the geography of the Fox Valley is the 

 first of a series of regional surveys on the State 

 of Wisconsin, U.S.A. Three years ago the Wis- 

 consin Geological and Natural History Survey pub- 

 lished an introductory survey devoted to the 

 State as a whole. The present volume (Bulletin 

 xlii.. Educational Series, No. 5) is by Prof. R. H. 

 Whitbeck, and, like the preliminary one, is pub- 

 lished by the State. The object of the work is 

 educational in the main, and the study of geography 

 in the schools of the district will certainly be helped 

 by the use of this intensive survey of a small region. 

 Physical considerations occupy but a small part of 

 the volume, which is mainly concerned with cities 

 and industries. The requirements of school children 

 appear to have been kept well in view throughout, 

 and yet the book avoids being either trivial or 

 didactic. 



The question of the nature and origin of the minute 

 plates that impart the " aventurine " effect to felspars 

 appears to have been finally solved by Olaf Andersen 

 ("An Aventurine Feldspar," Amer. Journ. Sci., 

 vol. xl., 1915, p. 351)- The author, after goniometric 

 and optical investigation, adopts Scheerer's view, put 

 forward in 1845, that the substance present is haema- 

 tite. His research covers American albites, oligoclase 

 from Kragero and Tvedestrand (sunstone), labradorite 

 from Labrador, and several microclines. The plates 

 are found always to be oriented after simple crystal 

 forms, although these forms may not be present in 

 the felspar crystal ; but the edges of the plates do not 

 yield simple crystallographic relations. These edges, 

 however, are referred to a mineral with hexagonal 

 or trigonal symmetry. The author believes that 

 FejOj was originally present in solid solution in the 

 felspar, either as haematite or as a constituent of a 

 ferric compound ; a disturbance of equilibrium, perhaps 

 a temperature-change, has caused it to separate out as 

 individual crystals of haematite along structural planes 

 of the felspar. The bluish tints of the schillerised 

 moonstones, murchlsonites, and labradorites are said 

 NO. 2437, VOL. 97] 



to be due, like the blue of the sky, to the " scattering 

 of light by particles smaller than the wave-length of 

 light, and cannot be explained as ordinary interference 

 colours of thin films." 



In the Journal of the Washington Academy of 

 Sciences for June 4 Mr. Paul D. Foote, of the U.S. 

 Bureau of Standards, shows how the melting points 

 of metals, e.g. tungsten, can be determined from the 

 luminosity of the molten metal. The radiation at 

 absolute temperature 6 of a black body between 

 wave-lengths X and X + ^X being taken as CiX'-'e-^it^^d . d\, 

 where c, and c, are constants, that of a metal over 

 the visible part of the spectrum the author repre- 

 sents by i\X~^e~^2/>^^ . Aef/^ . ei^ifil^ . d\, where p and g are 

 constants. If V(X) is the visibility of radiation X, the 

 luminosity of the surface of the metal is 



A^/9 .cj\- 5^-^2A(i/«-/) . Y(\)d\. 



On writing ijO' = ijd--py this becomes 



A^?/«. fj J X-V-2'Arv(X)^X, 



which, with the proper value of V(A), has been 

 shown graphically to reduce to Aegl^ . P{(^' + B)/(^' + C)fi', 

 where P, B, C, D are constants. In the case of 

 tungsten the author shows that the values of the 

 constants are A = o-303, ^=i'o4xio~*, ^ = 322, 

 C2= 14450, B= — 106, € = 265, D = 72, P= 1-91x10-^. 

 From Langmuir's observation that at the melting 

 point tungsten has a luminosity of 6994 candles per 

 square centimetre, it is shown that the preceding 

 constants give 3712° as the absolute temperature of 

 the molten surface. This method of determining high 

 temperatures seems likely to prove of great value. 



The Mathematical Gazette for May contains a 

 paper by Prof. H. S. Carslaw entitled "A Progres- 

 sive Income Tax," dealing with the complicated 

 system of taxation adopted in Australia. Although 

 the British Chancellor of the Exchequer took his 

 B.A. degree in the Cambridge Mathematical Trif>os 

 in 1886, he seems to have so far forgotten all his 

 mathematics that he has imposed taxes at the rates 

 of more than 2500, 5000, or 8000 per cent, on 

 persons whose incomes exceed loooi., 1500^., or 2000Z. 

 by a single pound. It would be more correct to say 

 that the rate becomes infinity in the pound at these 

 points of the scale, and the case may easily arise 

 in which a professional man may have to throw 

 up his duties at short notice in order to avoid losing 

 money by earning more. But in Australia they 

 appear to have gone to the opposite extreme, and 

 determined the rate of tax by complicated mathe- 

 matical formulae defined by curves of the second and 

 third degrees. Indeed, Prof. Carslaw has to use the 

 integral calculus in the examples that he works. 

 Why cannot Chancellors of the Exchequer bring a 

 little more common sense, as well as elementary 

 mathematical knowledge, to bear on income-tax 

 problems? The discontinuities in the gradient of the 

 income-tax curve, which the Australians have taken 

 so much trouble to eliminate, are of no very great 

 moment, while the present English discontinuities 

 in the total amount of the tax are open to serious 

 objection. With looZ. exempt, and rates of 25. 6d. 

 on the next 400Z., 45. on the next 500Z., and 55., 65., 

 and 7s. on subsequent additions to income of 500Z., 

 the average rate on 2500Z. would be very nearly 55. 

 in the pound, but the man with 2000Z. who earned 

 an extra iZ. would still gain 135. instead of losing 

 more than 50Z. or 80Z. 



The statement that, since the war began, Germany 

 has succeeded in obtaining her full supply of nitrates 



