May 12, 1904] 



NATURE 



41 



suggested why this stepping should be so marked a feature 

 in iron, while it is so comparatively rare in certain 

 other metals. This reason is that the ferrite crystals in 

 ordinary iron and steel are formed by crystallisation 

 from a solid solution, while the ordinary crystals of 

 lead, for instance, are formed by crystallisation from a 

 true liquid. The truly crystalline character of slip-bands 

 is further demonstrated in a novel manner by the observ- 

 ation of slip-bands in iron following and revealing the 

 gliding planes of twin crystals. Finally, the view has been 

 advanc-ed that the strength of inter-crystalline cohesion in 

 pure metals and certain forms of alloys is due to the inter- 

 locking of the skeleton arms which the crystals develop 

 ■during their first formation. According to this view, the 

 jnter-crystalline boundaries take the form of regions of 

 mixed orientation, and certain consequences are to be de- 

 <iuced from this consideration. It is argued that, since a 

 region of mixed orientation must offer greater resistance 

 ■to slip than a region of uniform orientation, the inter- 

 crystalline boundaries form a network of cells upon which 

 <he true resistance of the metal depends. Plastic deform- 

 ation sets in when these cell-walls begin to give way ; in 

 •doing so they carry with them the less resisting masses 

 of the crystalline grains. In this way the observed relation 

 between slip-bands and inter-crystalline boundaries is ex- 

 plained. Obsen-ations of a frequent doubling of the inter- 

 crystalline boundaries between ferrite grains in pure iron 

 and the " bordered boundaries " and " spines " in strained 

 metal are adduced as further evidence in support of this 

 view of the structure of inter-crystalline boundaries. 



Mr. B. H. Thwaite (London) contributed a paper on the 

 •use of steel in .-Vmerican lofty-building construction. 

 During the past five years some 200,000 tons of steel have 

 fceen annually consumed in steel frame construction in the 

 United State's. 



Mr. P. Breuil (Paris) submitted a report on the work 

 carried out by him as a Carnegie research scholar. It 

 •dealt with the relations between the effects of stresses slowly 

 applied and of stresses suddenly applied in the case of iron 

 and steel. He showed that the tests made with nicked bars, 

 a widely extending practice in France, were just like those 

 made with plain bars, but much less clear and precise. 

 The nicking of test bars simply introduces a further com- 

 plication. 



Mr. P. Longmuir (Sheffield) submitted a report on his 

 ■research, as a Carnegie scholar, on the influence of varying 

 casting temperature on the properties of steel and iron cast- 

 ings. With mild steels the influence of casting temperature 

 ■does not appear to show on the tensile properties. Low 

 casting temperatures, however, appear to induce a type of 

 brittleness not evidenced in the tensile test, but shown in 

 the working life of the metal. It is possible that many 

 of the mysterious fractures of steel, which has previously 

 passed a rigorous inspection, may be traced to the original 

 ingot having been cast at too high or too low a temperature. 



THE SOUTH AFRICAN ASSOCIATION. 

 *T*HE second annual meeting of the South -African 

 .'\ssociation for the .Advancement of Science was held 

 at Johannesburg during the week commencing April 4. 

 At the opening meeting Lord Milner presided, and Sir 

 ■Charles Metcalfe delivered his presidential address, which, 

 an addition to a review of the scientific advances during 

 the preceding year, contained a number of comments on 

 some of the causes which have effected the great advances 

 in scientific knowledge in recent years. 



Portions of the address appeared in the Johannesburg 

 Star, and we have selected from them a few extracts of 

 ■scientific interest. The only address which has reached 

 us is one given by Mr. E. B. Sargant on " The Education 

 of Examiners,'* and an abridgement of this will probably 

 appear in our next number. For the subjoined abstracts 

 of other addresses and papers we are indebted to the 

 Johannesburg Star. 



Presidenlial Address. 

 Referring to diseases of stock. Sir Charles Metcalfe 

 said : — In Rhodesia, Dr. Koch has been spending the whole 

 year in laborious and patient investigation of the .African 



coast fever among cattle, and he has now reported that he 

 has found that it is caused by a blood parasite which can be 

 readily identified by a demonstration of the specific 

 organism, that it is different from Texas fever, or so-called 

 red-water, that it is not transferable directly, that sick 

 animals can be stabled with healthy ones without com- 

 municating the disease, and that the disease can only be 

 spread by ticks. Further, that the blood of animals which 

 have recovered and become immune is not free from para- 

 sites, and that the disease therefore can be produced in 

 healthy animals by the transfer of parasites from salted 

 animais by means of ticks, and though fencing, dipping 

 and spraying are beneficial, yet as they have only a tem- 

 porary value. Dr. Koch recommends that these precautions 

 should be supplemented by inoculation with the blood of 

 animals that have recovered whenever disease breaks out 

 in the vicinity. 



Turning to another subject, the president continued : — 

 the geodetic survey of Africa, the inception and continuation 

 of which owe so much to our past president. Sir David 

 Gill, is being proceeded with both in the Transvaal and in 

 northern Rhodesia beyond the Zambezi. It is intended tc 

 extend it northwards more or less, probably along the route 

 of the Cape to Cairo railway, that projected line which to 

 many appears, perhaps, to belong to the things of dream- 

 land. You, however, who know South Africa well will 

 agree with me that in this country it has generally been 

 found that the sanguine man has ever been the truest 

 prophet. When this geodetic survey has been connected 

 up with that of Europe, which has now been extended as 

 far north as Spitsbergen, we shall have an arc from that 

 point to Cape Town — the longest arc that is possible to us 

 on this globe. All civilised nations have found ^ the 

 advantage of having proper and accurate maps, and it is 

 hoped that a useful work may now be undertaken in South 

 .Africa by a system of secondary triangulation. This work 

 will necessarily take many years to complete ; every year, 

 however, the recorded results will be of value, as they will 

 enable correct maps to be compiled showing the topography 

 and main features of the country and the situation of the 

 larger farms, of the most important and more populated 

 districts in the first place, and then of the more remote 

 parts of the country. 



Introducing the subject of anthropological research, the 

 president remarked that Prof. Haddon, when president 

 of the .Anthropological Institute, expressed himself strongly 

 on the urgencv of anthropological research. " In 

 view," he said, " of the decrease of the native races by 

 the advance of civilisation and the changes in the habits of 

 the survivors, no time is to be lost in the acquisition of 

 scientific knowledge by direct observations." There is 

 wide scope and much opportunity in South Africa for such 

 research, though Sir Charles Metcalfe said " the argument 

 about their decrease and the use of the word ' survivors ' read 

 strangely to us, who see the native races not decreasing but 

 happilv increasing in numbers as well as in material 

 prosperitv." 



Later in his address Sir Charles Metcalfe directed atten- 

 tion to the fact that for research into the causes and pre- 

 ventives of disease, both in human beings and in animals, 

 there is a great field in South Africa. Continuing, he 

 remarked, " The various Governments here have shown 

 commendable vigour in dealing with those terrible scourges, 

 rinderpest, plague, and red-water, and have acted 

 in a spirit of the truest economy by securing the services 

 of the most able men of science of the day in their investi- 

 gation. When England was ravaged by rinderpest, no 

 remedy was discovered ; the animals affected were simply 

 destroyed at a cost of some nine millions of money. It 

 was left for South Africa, at a later date, when knowledge 

 was more advanced by the admirable work of the scientific 

 investigators engaged on that task, to be the first_ to dis- 

 cover a preventive for that disease, a fact of which this 

 country may well be proud. I have mentioned Dr. Koch's 

 great work in the investigation of cattle fever in Rhodesia. 

 He has also at the same time undertaken researches into 

 some others of the diseases affecting animals in South 

 .Africa, amongst them that most familiar but terrible dis- 

 ease which we call horse-sickness, a disease by which the 

 country loses not only many thousands of pounds annually 

 bv the deaths of valuable animals, but also the large amount 



SO. 1802, VOL 70] 



