43f) 



NATURE 



[December 17, 1914 



lands of the Sink are widely different from those 

 hitherto investigated in the case of Krakatau, the 

 cooling lavas of the Hawaian Islands, newly-made 

 land about the mouths of rivers, etc. The chief 

 features in the re-vegetation of the beaches successively 

 exposed each year by the recession of the water are 

 described in detail, but the following- were the chief 

 points to be taken into account in noting the progress 

 of re-vegetation. As the salt content of the water 

 increased by about i8 per cent, in each succeeding 

 year, each emersed strand would be saturated with a 

 soil solution of the concentration and composition 

 prevalent in the period preceding emergence, and the 

 desiccation of the emersed strands would proceed at a 

 rate determined by the character of the soil [e.g. 

 its capillary raising power), and by the composition of 

 the infiltrated lake water. The re-vegetation of the 

 strand bared in 1907 was chiefly due to the rising 

 water picking up seeds lying on the surface and leav- 

 ing them on the wet flats, but since that year the 

 plants invading the new strands were carried there 

 as seeds by the wind, by flotation, or by birds, only 

 those plants surviving as could withstand the rapid 

 warming of the shallow water on the mud flats, which 

 increased its toxicity for seeds and seedlings, and the 

 rapid desiccation of the surface soil, which increased 

 the difficulties of the rooting and establishment of the 

 plants. 



The report is illustrated by thirty-two beautiful 

 -collotype plates, and interesting as are the results 

 already obtained, the continued investigation of the 

 phenomena presented by the re-vegetation of this steri- 

 lised desert basin area under difficulties which will 

 become increasingly great as evaporation proceeds will 

 doubtless vield even more valuable results in the 

 future. ' F. C. 



FINISHING TEMPERATURES OF RAIL 

 STEEL. 



■p EPRINT No. 38 of the Technologic Papers of the 

 -■-^ Bureau of Standards, by Messrs. Burgess, 

 Crowe, Rawdon, and VValtenberg, deals with observa- 

 tions on the finishing temperatures and properties of 

 steel rails. The principal objects of the research were 

 to " determine from measurements taken in repre- 

 sentative rail mills, the present American practice re- 

 garding the temperatures at which rails are rolled, to 

 demonstrate the ease and accuracy with which such 

 temperatures may be measured, and to find out what 

 the * shrinkage clause ' in rail specifications really 

 means." 



The authors have found that ingots for rails are 

 rolled at temperatures ranging from 1075° to 1150° C, 

 and that the variation from one ingot to another in a 

 series of 20 to 40 is only 10° to 20° C. The rails are 

 finished at temperatures which may vary between 

 S8o° and 1050° C, but which usually come within 

 50° C. of 935° C. With uniform mill practice the 

 rails of loo-lb. section will be finished at some 10° 

 to 20° C. hotter than 90-lb. rails, and about 50° C. 

 hotter than 75-lb. rails. The melting or freezing 

 range of such steels extends from about 1470° to 

 1530° C, i.e. to nearly the melting point of iron. The 

 •critical Ac i point was found to occur within 7° C. of 

 732° C. for the ten samples of Bessemer and open- 

 hearth steels examined. On cooling the correspond- 

 ing Ar r point occurs between 680° and 650° C. 



In all cases, therefore, the temperature at which 

 the rolling of the rails ceases was at least 200° C. 

 above the critical point, and there is no doubt that 

 the rolling temperatures could with advantage have 

 been carried much lower than they actually were. 

 A rail of loo-lb. section, cooling freely in the air from 



NO. 2355, VOL. 94] 



1070° C, reaches the recalescence point (Ar i) in aboii: 

 8i minutes ; and the maximum difference in tempera- 

 ture between the centre and the outside of the head is 

 about 85° C. at 1000° C, becoming 0° at the re- 

 calescence point. A comparison of the " shrinkage 

 clause" specification with the expansion of rail steel 

 shows that this clause permits the finishing of rails 

 at 1120° C, which is 450° C. above the critical range 

 of such steel and is above the temperature at which 

 many rail ingots are rolled in practice. In its present 

 form, therefore, the clause has absolutely no signifi- 

 cance. 



FOREST ENTOMOLOGY. 



A VALUABLE Bulletin (Entom., No. 7) of the 

 Canadian Department of Agriculture on forest 

 insect conditions in British Columbia, has been 

 lately issued by Mr. J. M. Swaine. The author deals 

 mostly with the Scolytidae injurious to the more im- 

 portant species of pine, spruce, and fir; he gives in- 

 teresting summaries of the life-histories, illustrated by 

 excellent figures of the beetles, their larvae, and their 

 characteristic brood-galleries in the bark of the trees. 



The " large larch sawfly " (Nematus crichsonii) — 

 notorious for its ravages in the Cumbrian Lake dis- 

 trict — continues to occupy the attention of zoologists 

 in the University of Manchester. Mr. R. A. Wardle 

 contributes to the last number of the Journal of 

 Economic Biology (vol. ix.. No. 3) some notes on the 

 life-histories of two of its parasites hitherto un- 

 recorded ; these are Zenillia pexops, a Tachinid 

 dipteron, and Hypamblys albopictus, an Ichneumon- 

 fly. The first-stage larva of the latter, with its rela- 

 tively big head, elongate tail-process — variously inter- 

 preted as a blood-gill or a pro-leg — and paired, limb- 

 like outgrowths on the body-segments, is remarkable. 

 Several of these young grubs may occur in one sawfly 

 caterpillar, but apparently only one of them is able 

 to pass through the subsequent larval stages and 

 become in due course a pupa. There appears to be 

 rather severe competition among the various parasites 

 of the Nematus, so that there may be danger of their 

 weakening one another in the process of reducing the 

 numbers of their host. 



The pine weevil (Hylobius abietis) is one of the most 

 abundant of our native woodland insects. Mr. J. W. 

 Munro has lately published (Proc. R. Phys. Soc. 

 Edinb., vol. xix., No. 6) the fullest account yet avail- 

 able of the reproductive organs in both sexes. 



AUSTRALIAN HANDBOOKS FOR THE 

 BRITISH ASSOCIATION.^ 



IN connection with the recent meeting of the British 

 Association in Australia, official handbooks were 

 issued for the Commonwealth and for all the States — 

 Western Australia, South Australia, Victoria, New 

 South Wales, Queensland, and Tasmania. Copies of 

 all were distributed among the visiting party, in most 



1 The Commonwealth of Australia. Federal Handbook prepared in con- 

 nection with the 84'h meeting of the British .^ssoriation for the .\dv.ance- 

 ment of Science, held in Australia, August, 1914. Edited by G. H. Knibbs. 

 Pp. xvi + sgS. (Melbourne: Mullett.) 



Handbook and Guide to West«-rn Australia. Prepared for the Members 

 of the Advance Party of the British Association for the Advancement of 

 Science. Pp. vi + ii8. (Perth: F. W. Simpson, igi4.) 



Handbook of South Australia. British Association for the Advancement 

 of Science. Australian Meeting, iqu. Adelaid-. Toint Editors : D. J, 

 Gordon and V. H. Ryan. Pp. 328. (Adelaide: R. E. E. Roeers. 1914.) 



British Association for the Advancement of Science. Australian Meeting, 

 1914. Handbook to Victoria. Prepared under the direction of the Victorian 

 E.vecutive Committee, by A. M. I.aughton and Dr. T. S. Hall. Pp. xvi + 

 382. f Melbourne: A. J. Mullett, 1914.) 



British Association for the Advancement of Science, 1014- Handbook for 

 New South Wales. Pp. xiv-T-621. (Svdney:E Lee and Co.) 



Our First Half-Century. A Review of Queensland Progress. By 

 Authority of the Government of Queensland. Pp. xxviii f 258. (Brisbane : 

 A. I. Cumraing, igog.) 



British Association for the Advancement of Science. Tasmanian Hand- 

 book. Pp. iv-r348. (Hobart : J. Vail, 1914) 



