September 24, 19 14] 



NATURE 



99 



the size of plaice to be landed. The results of Dr. 

 Johnstone's plaice-marking experiments are also 

 given. 



Mr. William Riddell continues his hydrographical 

 investigations, and the results of the chemical analyses 

 of the water samples and a drssertation on their 

 import are given by Prof. Bassett. As part of a pro- 

 posed general scheme of investigation of the British 

 herring races arranged by the Board of Fisheries, I 

 several samples of herrings from the Welsh coast and 

 from the Smalls were examined and the measurements 

 are detailed in the report. A paper of a preliminary 

 nature on sea-bottom deposits and fish food off the 

 Lancashire and Cumberland coasts is contributed by 

 Mr. R. Ray. Dr. Johnstone gives a topographical 

 description of the mussel grounds in the Ribble 

 Estuary and several other Welsh beds. From the 

 results of a bacteriologial analysis, also given, much 

 sewage contamination seems to exist at several of the 

 grounds. 



Two important papers by Prof. Moore and his col- 

 laborators are given on the debated question of the 

 ability of marine animals to subsist on the organic 

 carbon dissolved and in suspension in sea-water. The 

 results seem to prove conclusively that such subsist- 

 ence for long periods is impossible, and that neither 

 dissolved organic matter nor the average amount of 

 suspended plankton suffices to account for the nutri- 

 tion of the larger marine organisms. 



Several minor reports conclude the survey of the 

 vear's work. 



THE METROPOLITAN WATER SUPPLY.^ 



THE two reports by Dr. A. C. Houston, director 

 of water examination, recently issued by the 

 Metropolitan Water Board, show how n*uch is now 



ing done to safeguard from contamination with 

 . uigerous micro-organisms the metropolitan water 

 supply, which is admittedly largely derived from 

 sewage-polluted sources. The eighth annual report 

 gives the results of the chemical and bacteriological 

 examination of the London waters for the twelve 

 months ended March 31, 1914. In the introduction 

 Dr. Houston points out that experience in the W^ater 

 Board laboratories indicates that Bacillus coli is prac- 

 tically totally absent from pure waters ; In ten specially 

 devised experiments with the Twins well (Deptford) 

 water, typical B. coli was absent from 10,000 c.c, 

 and it has been abundantly shown that it is possible, 

 at a not impracticable cost', so to purify the raw river 

 waters that the final product contains no typical 

 B. coli in 100 c.c. in more than 80 per cent, of the 

 samples. 



In the tenth report on research work, the results of 

 several important researches are detailed. The search 

 for the typhoid bacillus and similar micro-organisms in 

 raw river water and crude sewage has been continued, 

 but although a large number of samples has been 

 examined, none has been found. Various methods for 

 the isolation of the typhoid bacillus in these circum- 

 stances are reviewed. 



A study of the streptococci present in excremental 

 matters has not resulted in finding any definite differ- 

 ence between those present in human, and those pre- 

 sent in animal, excrement. 



The value of storage as a means of eliminating 

 pathogenic micro-organisms and of lime as a bacteri- 

 cidal agent are further confirmed in series of new 

 experiments. 



1 Metropolitan Water BoarH (a) " Eie'ith Annual Report " on the results 

 of the Chemical and Bacteriological Examination of the London Waters 

 for the twelve months end'd March n, igi4. (*) "Tenth Report on 

 Research Work." Both by Dr. A. C. Houston, Director of Water Examina- 

 ion, Metropolitan Water Board. 



NO. 2343, VOL. 94] 



.Altogether these two reports are worthy of careful 

 perusal by public health authorities and bacteriologists, 

 and show how much valuable but unobtrusive work is 

 being done by Dr Houston and his staff. 



R. T. Hewlett. 



LOCAL CASE-HARDENING OF STEELE 



TN a paper read to the Socidte d 'Encouragement 

 -*• pour rindustrie National, MM. Guillet and Ber- 

 nard discuss the various methods employed when it is 

 desired to case-harden steel objects in certain parts 

 only. The methods used are : — 



(i) The parts to be protected against cementation 

 are covered with fire-clay. The protection thus fur- 

 nished is not complete, as the gases penetrate the 

 fire-clay. Also in complex shapes the method becomes 

 complicated and expensive. 



(2) A tube is shrunk over the parts to remain un- 

 cemented, the thickness of the tube being slightly 

 greater than the depth of case required. After the 

 end of th'fe cementing process, the tube is broken off. 

 This method is obviously very limited in its applica- 

 tion. 



(3) The object is made with extra thicknesses in 

 those parts which must not be hardened. After 

 cementation and before hardening, these extra thick- 

 nesses are machined off. This process is very ex- 

 pensive. 



(4) The parts not to be cemented are protected by 

 a metallic deposit which must be (a) solid at the 

 cementing temperature, (6) impervious to the cement- 

 ing materials, (c) easily obtained commercially, and 

 (d) easily removed after the operation. Copper and 

 nickel are the only metals which fulfil conditions 

 (a) and (c), and the latter fails to comply with con- 

 dition (b). 



The metal may be deposited by immersion in a salt 

 solution, by electrolysis, or by the Schoop spraying 

 process. The first mentioned is not satisfactory owing 

 to the thinness and uncertain adherence of the coating. 

 The electrolytic process is cheaper to instal than the 

 spray process, which, on the other hand, is quicker 

 and more easily localised. 



The authors also consider the question of diffusion 

 of metals. They show that for this to take place, 

 (i) the two metals must be capable of forming solid 

 solutions with each other, (2) they must be in very 

 good contact, and (3) the temperature must be between 

 the limits at which the solid solution exists. The 

 higher the temperature, the greater is the rate of 

 diffusion. They conclude that the diffusion of solids 

 into solids is a ver\- common phenomenon, which in 

 certain cases (e.^. tinned condenser tubes) may intro- 

 duce very considerable changes into the properties of 

 the metal. 



THE AUSTRALIAN MEETING OF THE 



BRITISH ASSOCIATION. 



SECTION K. 



BOTANV. 



Opening .Address by Prof. F. O. Bower, D.Sc, 



F.R.S., President of the Section. 

 To preside over the botanical section on the occasion 

 of its first meeting in Australia is no slight honour, 

 though it also imposes no small responsibility. We 

 members from Great Britain have a deep sense of 

 the advantage which we derive from visiting these 

 distant shores. I am doubtful whether any scientific 



1 Les reserves en cementation et la diffusion dan* les solides." By MM. 

 Lion Guillet and Victor Bernard. Bulletin de la Socilti d^ Encouragement 

 pour C Industrie Nationale, vol. cxxi. No. 5. Pp. 588-618. 



