572 



NA TURE 



[October 5, 1905 



the successive washing up of beaches from the sea, en- 

 closing areas of the reef. On the whole, there is singularly 

 little change since the survey in 1837, and my impression 

 is that Chagos has been for a long time an area of rest, 

 and that the present condition of its reefs is mainly due 

 to agencies still in action. 



We have now examined the marine fauna in Salomon, 

 Peros Banhos, Diego Garcia, and Egmont, and I would 

 again lay stress on its comparative paucity and lack of 

 variety as compared with the Maldives, Fiji, or even 

 Funafuti, though many of the forms are very common. 

 In short, its general character is rather that of the 

 temperate than of the tropical zone. 



The land fauna is largely dependent on the flora, and 

 the latter, except on small isolated islets and selected 

 positions, has been destroyed to allow of cocoanuts being 

 planted. The shores are everywhere fringefi with Scaevola 

 koenigii and Tourncforlia argentea, both covered with a 

 climbing bean. Behind these there was originally a forest 

 formed of immense mapon (Pisoiiia capidia) and taliamaka 

 (Calophyllum inophyUum), with a few cocoanuts, Barring- 

 tonia, banyans, and other smaller trees, and an under- 

 growth largely consisting of immense Asplenium and other 



I the Seaward Reef of Salomon Atoll, Chago: 



ferns and Psilotum, herbaceous dicotyledons being con- 

 fined to the more open, dry, sandy, and stony parts ; 

 mangroves and Pandani are, curiously enough, not found. 

 With the assistance of Dr. Simpson, we have collected the 

 flora of each of the atolls, obtaining more than 600 speci- 

 mens, about 140 species, of which probabiy only half are 

 indigenous. 



Of mammals there are only rats and mice, but there are 

 traditions of dugong as well. Of birds the cardinal, 

 sparrow, and mina have doubtless been introduced ; 

 noddies, frigates, and terns were breeding in enormous 

 numbers on certain islands, though it was mid-winter ; 

 crab-plover, curlew, whimbal, and a sandpiper were 

 common, and in the north-west monsoon buzzards, kites, 

 and crows are said to be regular visitants. The green 

 and shell turtles (Chclone mydas and C. imbricata) abound, 

 the former coming on shore to deposit its eggs at night 

 and the latter in the daytime. The only other reptiles 

 are a marsh tortoise, perhaps introduced from Madagascar, 

 and geckoes ; there are no Amphibia. There is only one 

 land shell, and arachnids and myriapcds are scanty ; the 

 land Crustacea are similar to those of the Maldives, but 

 the coco crab {Birgus latio) is also abundant. Mr. Bain- 



NO. 1875, VOL. 72] 



brigge Fletcher has sorted the insects and finds about 



10 species, most of which are probably indigenous ; but 



he best season for the group would be in the rather hotter 



and damper north-west monsoon. On the whole, the land 



auna and flora is much what one would expect to get, 



garding the Chagos as a group of purely oceanic islands. 



We expect to leave Mauritius toward the end of August 



or Cargados, Agalegas, and the submerged banks towards 



he Seychelles. Our cruise will be largely a dredging one, 



but the examination of Agalegas should be interesting. 



Meanwhile, Cooper and I hope to see some of the reefs 



round Mauritius. 



J. Stanley Gardiner. 



IRON AND STEEL INSTITUTE. 

 T70R the first time the autumn meeting of the Iron and 

 Steel Institute was this year held in Shefifield. An 

 elaborate programme of visits to works and social functions 

 was arranged, and no less than 1500 members and ladies 

 were present, including members from all parts of the 

 world. The opening meeting was held at the new 

 university on September 26 under the presidency of Mr. 

 R. .'\. Hadfield. Addresses of welcome 

 were delivered by the Lord Mayor, the 

 Master Cutler, the Vice-Chancellor of 

 the University, Colonel Hughes 

 (chairman of the reception com- 

 mittee), and by the president of the 

 Sheffield Trades and Labour Council 

 on behalf of the working men. Mr. 

 Hadfield, in reply, thanked the recep- 

 tion committee for the admirable 

 work it had done, and gave an 

 interesting historical review of the 

 Sheffield steel trade. Incidentally, he 

 mentioned that the membership of the 

 i r*:>n and Steel Institute had now risen 

 iM 2200. After the reading of the 

 minutes of the last meeting by the 

 secretary, Mr. Bennett H. Brough, 

 and the transaction of other routine 

 business, the papers submitted were 

 read and discussed. In the first paper 

 taken Prof. J. O. Arnold described 

 the department of iron and steel 

 metallurgy at the University of 

 Sheffield. The main object borne in 

 mind in designing the laboratory was 

 the erection on a manufacturing scale 

 of plant producing steel by the 

 crucible, Bessemer, and Siemens 

 processes. 



Prof. J. O. Arnold and Mr. A. 

 McWilliam next contributed an 

 important paper on the thermal trans- 

 formations of carbon steels. For the 

 research three steels were selected, 

 ith 0.89 per cent, of carbon, unsaturated 

 per cent, of carbon, and supersaturated 

 with 1-78 per cent, of carbon. In the case of the un- 

 saturated steel, the authors find that above Ar3 (810° C.) 

 the ferrite and hardenite are in mutual solution as a 

 homogeneous mass. The Ar3 change is accompanied by 

 a segregation of the two constituents, which, if the cool- 

 ing be slow, is probably completed in the Beta range of 

 temperature. After a fairly rapid cooling from 950° C. 

 the 0-2 1 per cent, carbon steel when quenched at 730° C. 

 micrographically registered a segregation of ferrite so far 

 advanced as strongly to suggest that such segregation must 

 have begun at Ar 3 and not at Ar 2. In other words, 

 hardenite is insoluble in ferrite in both the Beta and .^Ipha 

 ranges of temperature. It however still retains its identity 

 as hardenite whilst falling through, say, 30° C. or 40° C. 

 of temperature in the .\lpha range, namely, from the end 

 of Ar 2 at about 720° C. to the beginning of Ar i at about 

 680° C, at which latter temperature it begins to de- 

 compose into pcarlite. The heating transformations of 

 this steel arc substantially as follows : — At Ac i (about 

 710° C.) in the Alpha range the pearlite begins to change 

 into hardenite, hence the carbide is soluble in the 



chiijela 



saturated 

 with 0.2 



