August 19, 1920] 



NATURE 



787 



Jtvoted to the organisation of research, and we have 

 no doubt that the outcome will be of the greatest 

 benefit to both employers and employed. 



Copies of new editions of several pamphlets i-n the 

 Economic Series published by the Natural History 

 Museum have come to hand. No. i on the house-fly 

 {^usca domestica) by Major Austen is in its third 

 edition, and has been enlarged and almost entirely 

 rewritten. It deals with the house-fly under normal 

 conditions in the British Isles ; those who desire 

 further information, including Army requirements, 

 should consult the larger pamphlet, No. ia, in the 

 same series. The illustrations are exceedingly clear, 

 and several of these, along with the letterpress, will 

 help to distinguish the commoner house-frequenting flies 

 from the true house-fly, which they closely resemble. 

 Musca autumnaUs is a case in point; it frequently 

 enters houses, etc., and hibernates therein during the 

 winter, giving rise to the popular belief that the 

 winter habits of A/, domestica are well known. The 

 latter feature, however, is one concerning which we 

 need much more extensive observation than has been 

 accorded to it in the past. The breeding habits of the 

 house-fly are also dealt with, and simple remedial and 

 preventive measures against this pest are enumerated. 

 No. 3, by Mr. J. Waterston, deals with fleas and 

 their relation to man and domestic animals. It is 

 noteworthy that eleven species have up to the present 

 proved capable of transmitting plague. Five of them 

 are common in Britain, while the plague-flea par 

 excellence {Xenopsylla cheopis) is occasionally intro- 

 duced. No. 4, on mosquitoes, is written by a recog- 

 nised student of the family, Mr. F. W. Edwards. 

 The relation of these insects to disease and the control 

 measures in vogue are clearly explained. No. 6, by 

 Mr. H. Hirst, deals with scorpions, mites, ticks, 

 spiders, and centi[>edes in so far as they may be in- 

 jurious to man. Nos. 3 and 6 are reprints, without 

 alterations, of their predecessors, and No. 4 diff'ers 

 from its original edition only in a few small addi- 

 tions to the letterpress. 



An interesting account of the development of the 

 mica industry in Eastern Transvaal during the last 

 ten years is given by Mr. A. L. Hall in Memoir 13 

 of the Geological Survey of the Union of South Africa 

 (1920). The "books" of mica that are of economic 

 value occur as constituents of coarse-grained pegma- 

 tites which cut the older granite of the Pietersburg 

 tlistrict. The memoir gives a review of the uses of 

 mica and of the qualities and occasional defects that 

 must be considered from a commercial point of view. 



Mr. Seitaro Tsjboi has published a complete study, 

 structural and petrographical, of the island volcano 

 <'i Oshima, the largest of the "Seven Islands" group 

 south-west of the Bay of Tokyo (Journ. Coll. of 

 Sci., Imp. Univ. Tokyo, vol. xliii.,,May 10, 1920). 

 Incidentally, he introduces a method for the deter- 

 mination as nearly as possible of the maximum and 

 minimum refractive indices of minerals represented 

 by minute crystal grains, by using a large number of 

 grains immersed in various liquids above a Nicol. 

 NO. 2651, VOL. 105] 



The great crater-ring formed by ancient ejecta is 

 now dominated by the recent central cone of Miha- 

 rayama, which is still active. The author is not 

 afraid of technical terms, and concisely describes the 

 volcano as consisting of "double homates— a somma 

 and a central one," and as "built up of numerous 

 layers alternately accumulated of rheumatitica and 

 clasmatica of basaltic nature." 



Mr. H. Valentine Davis sends us a copy of his 

 " Little Book about Snowdon," published by him at 

 Wistaston, Crewe. This is illustrated with sketches, 

 sketch-maps, and sections drawn to the same vertical 

 and horizontal scale, which should do much to interest 

 the visitor to Llanberis in the many features of scientific 

 interest that are so well displayed on Snowdon. It 

 is a forerunner of a larger guide-book, and hence 

 only the Llanberis path is treated as a route to 

 Y VVyddfa. Without being didactic, Mr. Davis intro- 

 duces the right touches at the right points, and gives 

 just enough to make the reader think. The section 

 showing the descent of the erratic maen d'ur arddu 

 from the back of the twm contains a lot of glacial 

 lore, and might well be enlarged as a typical .diagram 

 of cirque-formation for the class-room. This alone is 

 worth the sevenpence charged {Sd. post free) for this 

 unassuming but effective little pamphlet. Will Mr. 

 Davis consider in the quiet of " Noddfa " whether 

 he or his printers are responsible for " Grib Goch " 

 (regularly rep)eated), "fi'ynon," and "carreg"? 



The latest issue of the Journal of the Royal Statis- 

 tical Society (vol. Ixxxiii., part iii.) contains an 

 interesting paper by Mr. M. S. Birkett, statistical 

 oflicer of the National Federation of Iron and Steel 

 Manufacturers, on "The Iron and Steel Trades 

 during the War," which brings out very clearly 

 the efforts made by this industry to produce the 

 enormous supply of munitions of war that were 

 needed for the great struggle. The author makes 

 it clear that it was the character rather than 

 the quantity of material produced that had to be 

 modified. Thus in 1913 the total production of 

 pig-iron was about 10,250,000 tons, which had fallen 

 in 1914 to just under 9,000,000 tons, and remained 

 approximately stationary at that figure throughout the 

 war. The classes of pig-iron used essentially for 

 steel-making, namely, haimatite and basic, had, how- 

 ever, risen from 58 per cent, to 72 per cent, of the 

 total, by far the biggest increase being in the latter 

 class, the output of which in 1918 was 50 per cent, 

 above that of 19 14. There was a corresponding in- 

 crease in the output of steel, which reached 9,500,000 

 tons in 1918, an increase of 1,700,000 tons over 1914, 

 the bulk of the increase again being in basic steel, 

 of which there was above 50 per cent, more made in 

 1918 than in 1914. It is interesting to note that there 

 were employed on the blast furnaces 39,200 men in 

 July, 1914, as against 54,900 in July, 1919, so that 

 the efficiency of the men employed had gone down very 

 considerably. The total numbers employed in the 

 industry at those two dates were 304,000 and 376,300 

 respectively, or, deducting those employed on blast 

 furnaces, ironfounding, and tinplate manufacture, 



