270 



NATURE 



[November 4, 19 15 



The recently issued part (part i., vol. vi.) of the 

 Annals of the Royal Botanic Gardens, Peradeniya, is 

 almost entirely occupied by a series of papers by Mr. 

 T. Fetch, the Government botanist. Of these the 

 most important contribution is that on " Horse-hair 

 Blights," belonging to the genus Marasmius. M. 

 equicrinis is the common species of the eastern tropics, 

 while M. sarmentosus is the species found in the West 

 Indies. Mr. Fetch devotes his attention to the Ceylon 

 species, which are described in some detail and illus- 

 trated by an excellent series of plates. The mycelium 

 of these fungi is thin and rhizomorphic, and spreads 

 freely over bushes and trees at some height above the 

 ground; the pileus is borne on a slender petiole, and 

 bears only a small number of gills. 



A COLLECTION of fungi from Australia and New 

 Zealand made by Mr. W. N. Cheeseman during the 

 visit of the British Association to Australia and New 

 Zealand last year is described by Miss E. M. Wake- 

 field in Kew Bulletin No. 8. Twenty-^ight of the 

 loo species enumerated are endemic to Australia, and 

 these include the seven new species described. Five of 

 the new species show close affinity with European or 

 North American types. Forty-eight species were found 

 to be common to Europe or North America,' sixteen 

 to the tropics of Africa and the East, and six cosmo- 

 politan in the tropics generally. Only two species 

 occur in the tropics of South America as well as in 

 Australia. Attention was paid especially to the Poly- 

 poraceae and Thelephoraceae, and the collection con- 

 sists mainly of specimens belonging to these groups. 

 The principal features of the new species are illus- 

 trated in the plates. 



Symons's ■ Meteorological Magazine for October 

 gives some very interesting details on the rains for 

 September, which varied considerably in different 

 parts of the British Isles. The rainfall table shows 

 an excess of rain in parts of Scotland and in the south- 

 east of England, whilst elsewhere there was a 

 deficiency. At Gordon Castle the excess for the 

 month amounts to 3- 17 in., the fall being 222 per 

 cent, of the average, whilst at Seathwaite the de- 

 ficiency for the month was 920 in., the fall being 

 only 18 per cent, of the average. A special article is 

 given on the floods in the north-east of Scotland 

 which occurred in the closing week of September, 

 when the floods are stated not to have been equalled 

 in many districts since the famous Moray floods of 

 August, 1829. The area of maximum rainfall was 

 located on the shores of Moray Firth, near Inverness, 

 the fall for the twenty-four hours on September 25 

 being 407 in. at Fortrose, 3-78 in. at Nairn, and 

 364 in. at Inverness. The total fall for the three 

 rain days September 24, 25, and 26 amounted to 

 5-47 in. at Nairn, the rain really falling in about 

 forty hours. The river at Nairn overflowed its banks 

 and occasioned much damage, whilst sixteen bridges 

 and culverts were carried away. The Daily Weather 

 Charts issued by the Meteorological Office show very 

 distinctly the advance and movement of the cyclonic 

 disturbance which occasioned the rainfall, the central 

 area being situated over the south of Scotland on the 

 morning of September 25. The rainfall in the south- 

 NO. 2401, VOL. 96] 



east of England on September 29, which caused an 

 excess for the month, was due to the passage of a 

 cyclonic disturbance along the English Channel, and 

 centred over the Straits of Dover on September 29. 



An interesting account of attempts to improve the 

 somewhat primitive methods used in certain of the 

 native industries of India is found in a paper by Mr. 

 A. Chatterton, in Bulletin No. 55 of the Agricultural 

 Research Institute, Pusa. It deals with the manu- 

 facture of jaggery in South India, and gives an 

 account of experiments made to introduce power- 

 driven sugar-cane mills as a substitute for the bullock- 

 driven mills hitherto universally used. A description 

 is also given of improvements in methods of evapora- 

 tion introduced with the object of increasing the yields 

 obtained from the juice ; with the existing wasteful 

 methods these are far lower than they should be. 



The October number of the Journal of the Rontgen 

 Society contains the interim report of the committee 

 on the standardisation of X-rays when administered 

 for medical purposes. It mentions most of the 

 methods of determining the quality or hardness and 

 the intensity of the X-rays falling on a surface, with 

 the intention of providing a proper basis for a more 

 extended discussion of the relative merits of the various 

 methods at a later date. On the whole the report 

 seems in favour of the half-value method of deter- 

 mining quality. The rays are sent through a stepped 

 wedge of a standard material — generally bakelite — and 

 fall on a fluorescent screen. Beside the wedge is 

 placed a metal plate with holes through it which 

 remove half its material, and the step of the wedge 

 which gives, on the screen, the same intensity of image 

 as the metal plate is noted. For determinations of in- 

 tensity the report apparently approves some form of 

 ionisation method, as most of the other methods give 

 undue weight to the softer rays. 



An important paper on the theory of grinding was 

 read at the Institution of Mechanical Engineers on 

 October 15 by Mr. J. J. Guest, of Birmingham. Apart 

 from side issues, the speed limit of the grinding wheel 

 is controlled by the strength of the material of the 

 wheel, and for reasons of production the wheel is to 

 be used at the highest safe surface-velocity. The 

 author considers that the component of the work- 

 velocity which is normal to the wheel surface (termed 

 the "normal material velocity") is the fundamental 

 controlling factor. This velocity is given by 



-.-y-^r 



dD 



where v is the surface velocity of the work, t is the 

 reduction in diameter being effected, and D and d 

 are the diameters of the wheel and work respectively. 

 This quantity, as has been said, is the controlling 

 factor, and if it is too large the wheel will wear 

 unduly, while if it is too small the wheel will glaze. 

 Again, the work done in grinding off metal is propor- 

 tional to the volume removed, i.e. the rate of grind- 

 ing, ^vtc, depends on the power used, c being the 

 traverse, vtc cannot exceed a certain amount, h, and 

 for production reasons should be kept up to that 

 amount, hence vt = h/c, together with the above 



