788 REPORT— 1895. 



percolation in reducing evaporation, and the influence of forests and vegetation in 

 increasino- tlie available rainfall, while equalising the flow of streams, are subjects 

 of equal interest to hydraulic engineers and meteorologists. 



Countries periodically visited by hurricanes, cyclones, or earthquakes, necessitate 

 special precautions, and special designs for structures ; and every additional in- 

 formation as to the force and extent of these visitations of nature is of value in 

 enabling engineers to provide more eft'ectually against their ravages. 



Benefits conferred by Engineering vpo7i Pure Science. — Engineering is generally 

 concerned in the application of the researches of science for the benefit of mankind, 

 and not in the extension of the domain of pure science, which necessitates greater 

 concentration of attention and study than the engineer in practice is able to devote 

 to it. Engineers, however, though never able to repay the ever-increasbg debt of 

 gratitude which they owe to past and present investigators of science, except in 

 rendering these abstract researches of practical utility, have, nevertheless, been 

 able incidentally to promote the progress of science. Thus mechanical science, by 

 the construction of calculating machines, the planimeter, integrating machines, the 

 tide-predictor and tidal harmonic analyser of Lord Kelvin, the self-registering tide- 

 gauge, and various other instruments, has lightened the labours of mathematicians ; 

 whilst excavations for works, and borings have assisted the investigations of geo- 

 logists. The mechanical genius of Lord Rosse led mainly to the success of his 

 gigantic telescope, which has revealed so many secrets of the heavens ; and the 

 rapidity of locomotion, due to the labours of engineers, has greatly facilitated 

 astronomical observations and physical discoveries, besides promoting the concourse- 

 of scientific men and the diffusion of knowledge. Electrical engineering, more- 

 over, is so closely allied to electrical physics that the development of the one 

 necessarily promotes the progress of the other. The observations also conducted 

 by hydraulic and maritime engineers in the course of their practice aid in extend- 

 ing the statistics upon which the science of meteorology is based. 



Engineering as an Experimental Science. — Engineering, so far as it is based on 

 mathematics, is an exact science, and the strains due to given loads on a structure 

 can be accurately determined ; but the strength of the materials employed has to 

 be ascertained before any structure can be properly designed. Accordingly, the 

 resistance of materials to tension, compression, and flexure, has to be tested, and 

 their limit of elasticity and breaking weight determined. Thus, pi'eviously to the 

 construction, by Robert Stephenson, of the Britannia Tubular Bridge, the first 

 wrought-iron girder bridge of large span erected, numerous experiments on various 

 forms of wrought iron were carried out by that eminent mathematician and 

 mechanician Eaton Ilodgkinson, who had previously indicated the proper theore- 

 tical form for cast-iron girders, and to whom the success of the bridge across the 

 Menai Straits was in great measure due.' Besides the numerous tests always now 

 made of the materials employed during the progress of any large engineering work, 

 railway bridges are also subjected to severe test loads before being opened for public 

 traffic, by which the safety of the structures and their rigidity, as measured by 

 the amount of deflection, are ascertained, serving as a guide for subsequent 

 designs. 



Numberless experiments have been made on the flow of water in open channels, 

 over weirs, through oritices, and along pipes ; and the influences of the nature of 

 the bed, the slope, depth, and size of channel, have been investigated by various 

 hydraulicians. Mr. Thomas Stevenson measured the force of waves at some places 

 on the Scotch coast;- Professor Osborne Reynolds has examined the laws of tidal 

 flow in a model of the inner estuary of the Mersey, and in specially shaped experi- 

 mental models ; ^ and I have found it possible, in small working models of the 

 Mersey and Seine, not merely to reproduce the configuration of the bed of the 

 estuary out to sea, but also to observe the efl'ects of difterent forms of training 

 "works in modifying sandy estuaries.'' Mr. "William Froude, after his retirement 



' The Britannia and Cumray Tubular Jiri/2{/r.i, Edwin Clark, vol. 1, p. 8.3. 



■ The JDesiyn and Construction of Ilarhui(r.i. Thomis Stevenson, 3rd ed. pp. 52-56. 



' British Associatiuii Beportx for 1889, 18i)0, and ]8'.)1. 



* Proceedings of the Boyal Society, vol. 45, pp. CO 1-524, and plates 2-4 ; vol. 47. 



