48 



NATURE 



[September io, 19 14 



tory of Civilisation," wrote : " Formerly the richest 

 countries were those in which Nature was most 

 bountiful ; now the richest countries are those in which 

 man is most active. For in our age of the world, if 

 Nature is parsimonious we know how to compensate 

 her deficiencies. If a river is difficult to navigate, or 

 a country difficult to traverse, an engineer can correct 

 the error and remedy the evil. If we have no rivers 

 we make canals; if we have no natural harbours we 

 make artificial ones." These words have a double 

 force at the present day and in the present surround- 

 ings, for nowhere has man been more active as a 

 geographical agency than in Australia ; and not inside 

 Australia only, but also in regard to the relations of 

 Australia to the outside world. 



An island continent Australia is still, and always 

 will be, on the maps. It always will be the same 

 number of miles distant from other lands; but will 

 these maps represent practical everyday facts? What 

 do miles mean when it takes a perpetually diminish- 

 ing time to cover them? Is it not truer to facts to 

 measure distances, as do Swiss guides, in Stunden 

 (hours)? What, once more, will an island continent 

 mean if the sea is to be overlooked and overflown? 

 The tendency is for the world to become one; and 

 we know perfectly well that, so far as distance is con- 

 cerned, for practical purposes the geographical posi- 

 tion of Australia has changed through the agency of 

 scientific man. If you come to think of it, what geo- 

 graphy has been more concerned with than anything 

 else, directly or indirectly, is distance. It is the know- 

 ledge of other places not at our actual door that we 

 teach in geography, how to get there, what to find 

 \yhen we get there, and so forth. The greatest revolu- 

 tion that is being worked in human life is the elimina- 

 tion of distance, and this elimination is going on 

 apace. It is entering into every phase of public and 

 private life, and is changing it more and more. The 

 most difficult and dangerous of all Imperial problems 

 at this moment is the colour problem, and this has 

 been entirely created bv human agency, scientific 

 agency, bringing the lands of the coloured and the 

 white men closer together. Year after vear, because 

 distance is being diminished, coming and going of 

 men and of products is multiplying; steadilv and 

 surely the world is becoming one continent. This is 

 what I want geographers to note and the peoples to 

 learn. Geographers have recorded what the world is 

 according to Nature. I want them to note and teach 

 others to note how under an all-wise Providence it is 

 being subdued, replenished, recast, and contracted by 

 man. •' 



SECTION G. 



ENGINEERING. 



Opening Address by Prof. E. G. Coker, M.A., D Sc 

 President of the Section. 



The subject of stress distribution in materials, which 

 1 have chosen for this address, is not one which an 

 engineer can claim as his peculiar province, for it 

 has been and still is a fruitful field of investigation 

 for the mathematician, the physicist, and the geologist 

 and has always been so since the commencement of 

 scientific inquiry; indeed, it must have been the 

 source of speculation and controversy ever since man- 

 kind emerged from a primitive state, and began to 

 fashion dwellings, weapons, and tools from the 

 materials at command. 



The development of architecture from the earliest 

 dwellings of savage races to the great temples of 

 bgypt and Greece, the bridges and aqueducts of the 

 Romans, and the mediaeval buildings of Europe, all 

 bear witness to the accumulation of practical know- 

 NO. 2341, VOL. 94] 



ledge of the properties of materials and of the stress 

 distribution in structures, which we cannot fail to 

 admire, although we know far too little of the way 

 in which these ancient structures were planned and 

 constructed. The magnificent arched and domed 

 buildings of the Roman period, and the stately cathe- 

 drals of later times with their wealth of architectural 

 form — tower and spire, flying buttress and vaulting — 

 all show how considerable was the practical know- 

 ledge of stress distribution possessed by the master 

 builders who planned and carried out these great 

 structures. We, who inherit these buildings as a 

 precious legacy of bygone ages, have at our command 

 far greater resources in the accumulated knowledge 

 of centuries of scientific discovery and invention, and 

 can build more complex structures^great bridges of 

 steel, towering frameworks covered by a thin veneer 

 of masonry, and floating arsenals of the most be- 

 wildering intricacy. All these we can show to our 

 credit as the result of the steady increase of scientific 

 knowledge applied to practical ends, but, even now, 

 knowledge of the stresses which come upon these 

 complex structures and machines is relatively small. 

 Scientific investigations of engineering problems of 

 stress still lag behind constructive ability, and de- 

 fective knowledge is obscured more or less by approxi- 

 mate theories and buttressed by factors of safety, 

 which serve in one instance perhaps, but show in 

 others that they have merely given a sense of fancied 

 security with no real basis, and are more properly 

 factors of ignorance, to be discarded at the earliest 

 moment. Who, for example, can say with certainty 

 what is the stress distribution throughout the com- 

 pression members of a great bridge, built up of com- 

 plicated steel shapes and plates, united by stiffening 

 angles, gusset plates, and innumerable rivets. There 

 is probably good reason for the belief that a great 

 strut is relatively weaker than a small one, when 

 both are designed according to the same approximate 

 formulae now used in current practice, and engineers 

 are unwilling to take the responsibility for such 

 members in a great structure, without providing a 

 very ample margin of safety to cover the contingencies 

 arising from lack of precise knowledge of the strength 

 of these members. So numerous are the problems 

 which arise in the design and construction of machines 

 and structures, that it is perhaps not unprofitable to 

 devote a short hour to the consideration of some of 

 the available means which an engineer can use as a 

 guide for his applications of science to construction, 

 since of whatever kind are the professional activities 

 he pursues, his place in the scheme of affairs mainly 

 depends on his ability to make machines and struc- 

 tures for directing and modifying natural sources of 

 power in known ways, or applying them to new pur- 

 poses as scientific discoveries advance the boundaries 

 of knowledge. 



The power to do this depends, to no small extent, 

 upon the ability to determine the distribution of stress 

 in a structure, and the skilful manner in which 

 material can be disposed for the required purpose. 



It is of some help to our appreciation of the achieve- 

 ments of the great constructors of past ages, if we 

 remember that they probably all held the erroneous 

 view that materials of construction are perfectly rigid 

 bodies, and, indeed, we know that as late as 1638 

 Galileo Galilei was of that opinion, and that he came 

 to an entirely wrong conclusion as regards the stress 

 distribution in a loaded cantilever. 



It required the genius and insight of Robert Hooke 

 to make a really great step, with his celebrated theory 

 of the linear relation of stress to strain, and we can 

 appreciate the glow of pride and satisfaction which 

 he must have felt at his great discovery, when he 

 records in 1675 that "his Majesty was pleased to see 



