G.— ENGINEERING. 121 



of its branches has been helped, and urged forward to further investigations 

 by the engineer stumbling on ground which science had not till then 

 investigated, in the particular manner in which engineering had need. By 

 collating results and making them applicable to the future needs of 

 engineering, the scientific worker has on many occasions determined 

 doubtful jjoints and made the future use of discoveries and inventions by 

 engineers and their allied workers possible. Thus, engineering practice and 

 engineering inventive imagination and pure science have reacted on one 

 another to the advancement of exactly applied knowledge. Simple facts 

 and discoveries by scientific research workers have frequently not revealed 

 their usefulness until those who apply them to the needs of men have 

 tested them and shown their utility, and then the scientific investigator 

 has made further advances, and indicated further possibilities in the 

 use of the discoveries made either by the laboratory research worker or 

 the engineer. My own experience, when dealing with practical civil 

 engineering problems, has indicated some examples, and many doubtless 

 exist unknown to me. The observation of natural phenomena has played 

 a very important part in the advancement of science as applied to industry 

 and to engineering problems of all kinds. The constructing engineer has 

 not the time to investigate exactly the forces of nature with which he has 

 to contend, and he has frequently to cover up his ignorance by the use of 

 ' factors of safety ' in making his designs, often using larger factors than 

 are called for, and at other times not providing the necessary margins he 

 thought he had allowed for. This is notably the case in connection with 

 bridge designs and stresses arising out of the fatigue of metals and the 

 hammer action of moving loads in bridge floor systems, and the efiect of 

 plunging rolling stock thereon. Investigations have been carried out 

 recently by experiments on a large scale with actual locomotives, the 

 results of which have been now collated by Prof. Inglis of Cambridge, into 

 some useful formulse, from which computations of possible stresses may 

 be foretold. Some types of locomotives have been so bad in this respect 

 that but for our old friend, the factor of safety, the structures of many 

 bridge floor systems would long since have been destroyed by percussion 

 and repeated hammer blows dealt upon them. It was long recognised by 

 engineers that the fatigue of metals under stress arising out of (1) the 

 range of stress, and (2) its reversal, demanded lower maximum stresses to 

 be applied, and the scientist has now so investigated the facts that 

 positive data are available and results can be forecast with accuracy and 

 certainty. Newton did not evolve the value of ' g ' out of his own mind, 

 but by observation its value was ultimately determined to the benefit of 

 all who use physical science. I do not know how we should get along 

 without ' g ' now, though apples fell long before it was discovered, and it 

 would be difficult to think how the influence of the planets upon our tides, 

 so important to many branches of civil engineering work, could have been 

 foretold but for the practical discoveries of Newton and their ultimate 

 scientific consolidation into mathematical formulae. There is still a great 

 deal to be discovered in connection with the action of tides and waves and 

 their destructive efiect on sea works, many of which fail undoubtedly from 

 f.he lack of exact knoAvledge of such action and their reaction on the sea 

 .shores where harbours must be built. Just recentlv we have had an 



