February 3, 192 1] 



NATURE 



739 



the fauna in a muddy creek of the Ganges to that of 

 the deep sea is assigned by Dr. Kemp to the common 

 factors of a niuddv bottom and low visibility. The 

 discovery that the peculiar sculpture of the shell in 

 rtain Viviparidae is connected with the persistence 

 wf structures present on the edge of the mantle in 

 the embryos of smooth-shelled forms bears on the 

 origin of the varied ornament in those molluscs. These 

 ;ind many other interesting results have suggested to 

 Dr. Annandale the need for a survey of the macro- 

 scopic fauna of the lakes of .\sia. 



At the request of Akierman F. C. Clayton, some 

 members of the botanical department of Birmingham 

 University visited the Birmingham Water Depart- 

 ment's reservoirs at Shustoke, near Whitacre, on 

 October 14 last. The water in the smaller of the two 



servoirs (about 8 acres in extent) had been drained 

 ft at the end of July for cleaning purposes, leaving 

 ;ie bottom covered to a depth of li ft. to 2i ft. with 

 .1 mixture of vegetation and mud. The small reser- 

 voir had not previously been cleaned, except at the 

 sides, since its completion in 1883. The vegetation 

 appeared to have consisted mainly of green alga:, 

 together with a number of aquatic flowering plants 

 iind a marginal zone of Fontinatis anlipyretica. The 

 alga; were represented by a number of genera, Clado- 

 phora fracta being the dominant species. An allied 

 species, probably a form of C. crispata, occurs regu- 

 larly in the slow sand filter-beds at the neighbouring 

 waterworks. During the cooler months this alga 

 often covers the bottoins of the filter-beds with a 

 matted felt of algal filaments, locally known as 

 'blanket weed." So long as the alga remains on 

 the bottom it appears to assist materially in the 

 process of filtration. On the advent of hot weather 

 the alga tends to rise, and has to be removed. 

 .\nothcr feature of interest is the very rapid colonisa- 

 tion by plants of (he drying, muddy bottom of the 

 reservoir. .Mthough only some two and a half 

 months had elapsed since the lowering of the water- 

 level, the surface of the mud was alrcadv occupied 

 by an open association of plants which included alga?, 

 together with patches of stunted land forms of 

 aquatic flowering plants. In addition to the true 

 aquatics, semi-aquatics, and even land plants, were 

 Spreading rapidly in a centrifugal direction over the 

 surface. 



On Friday, January 28, a general meeting of the 

 .'Association of Economic Biologists, presided over 

 by Sir David Prain, was held in the Imperial ("ollegc 

 of Science. Mr. E. E. Green showed a large (ias- 

 leropod which has been introduced into Ceylon, and 

 is now present in destructive numbers. Dr. Llewellyn 

 Llovd gave an account of his investigations on the 

 greenhouse white-fly and measures for its control, and 

 described interesting new details in the structure and 

 life-history of the insect. The only successful treat- 

 ment is hydrocyanic fumigation, this being carried 

 out at intervals of fourteen days in summer and of 

 twenty-five days during the winter months. Light is 

 a very important factor; the temperature should be 

 between ^o°-<)i>'^, and the dosage J oz. of sodium 

 cyanide to every 1000 cubic ft. space, .\tmosphcric 

 NO. 2675, VOL. 106] 



humidity is relatively unimportant, but if cyanide- 

 burning of the foliage is to be eliminated the plants 

 should have dry roots. .\n animated discussion took 

 place, in which Mr. Green, Prof. V. H. Blackman, 

 Dr. Imms, Dr. Hargreaves, Mr. Dykes, and Mr. 

 Emptage participated. Mr. Brierley then gave a 

 paper on " Personal Impressions of some .Vmerican 

 Biologists and their Problems." Mr. Brierley was 

 one of the three foreign representatives invited to the 

 .•\merican Phytopathological Congress in iqao, and 

 afterwards visited the principal scientific institutions 

 and many regions of botanical or agricultural 

 interest. 



The system of colour notation introduced by 

 Munsell in 1905 has been found of such practical 

 value by the manufacturers of colours and of coloured 

 goods in .\merica that the U..S. Bureau of Standards 

 has undertaken an examination of the system with 

 a view to its improvement. An account of the work 

 done by .Messrs. Priest, Gibson, and McNicolas forms 

 Technologic Paper No. 167 of the Bureau. Colours 

 are specified by their hue, their purity or chroma, and 

 their brightness, luminosity, or "value," and the 

 Munsell atlas contains coloured cards of six different 

 hues- — grey, red, yellow, green, blue, and purple — 

 each in different degrees of purity and luminosity. 

 These cards have been examined by means of the 

 spectrophotometer, and curves which show the 

 amount of light reflected of each wave-length are 

 given. From these it appears that the Munsell 

 "values" are proportional to the square roots of the 

 amounts of sunlight reflected, and the authors sug- 

 gest that in future editions of the atlas the numbers 

 indicating the luminosities should be proportional to 

 the logarithms of the reflections. In order to secure 

 this and other suggested improvements, the Optical 

 Society of .\merica and the Bureau are now con- 

 sulting those interested in colours. 



One of the largest steel-frame buildings which have 

 been constructed by welding methods in Great Britain 

 is illustrated in Engineering for January 14. This 

 building constitutes the new workshops of Messrs. 

 the Double .Arc Electric Welders, Ltd., and is situated 

 in Glasgow. The steelwork throughout was welded 

 by the company on its system. The name of this 

 firm is derived from the special flux with which it 

 coats its welding electrodes. The flux is conducting, 

 and it is claimed that an independent arc is formed 

 between the flux and the work, as well as the arc 

 between the electrode and the work; this gives the 

 double arc. The building is 27 ft. wide and 50 ft. 

 long ; there are five roof principals carried on columns 

 having welded-on bases. The roof principals are 

 built of angles and channels, both of which members 

 are welded to the webs of the columns. The secon- 

 dary members of the trusses, together with purlins, 

 etc., are all welded at the points of attachment. Even 

 the steel door-frames are welded. Electric welding 

 would appear to offer many points of advantage in 

 the field of construction, and is obtaining a sound 

 footing. 



The latest catalogue (No. 409) of Mr. F. Edwards, 

 83 High Street, Marylebone, W. 1, consists of par. 



