September 12, 1895] 



NA TURE 



469 



the theoretical and practical knowledge of the strength of timber 

 had obtained considerable development. But in 1830, before 

 the introduction of railways, cast iron had been sparingly used 

 in archefl bridges for spans of from 160 to 200 feet, and wrought 

 iron had imly been aiiplied to large-span irr)n bridges on the 

 suspension i)rinciple, the most notable instance of which was the 

 Menai Suspension Bridge, by Telford. Indeed, whilst the 

 Strength of limber had been patiently investigated by engineers, 

 the best form for the use of iron girders and .struts was only 

 beginning to attract attention, and the earlier volumes of our 

 Transactions contained numerous records of the researches of 

 Eaton Hodgkinson, Barlow, Rennie, and others. It was not 

 until tw'cnty years later that Robert Stephenson and William Fair- 

 bairn erected the tubular britlge at Menai, followed by the more 

 scientific bridge erected by Brunei at Saltash. These have now 

 been entirely eclipsed by the skill with which the estuarj* of the 

 Forth has been bridged with a span of 1700 feet by Sir John 

 Fowler and Sir Benjamin Baker. 



The development of the iron industry is due to the association 

 of the chemist with the engineer. The introduction of the hot 

 blast by Neilson, in 1829. in the manufacture of cast iron had 

 effected a large saving of fuel. But the chemical conditions 

 which affect the strength and other qualities of iron, and its 

 combinations with carbon, silicon, phosphorus, and other sub- 

 stances, had at that time scarcely been investigated. 



In 1856 Bessemer brought before the British /issociation at 

 Cheltenham his brilliant discovery for making steel direct from 

 the blast furnace, by which he dispensed w'ith the laborious pro- 

 cess of first removing the carbon from pig-iron by puddling, and 

 then adding by cementation the required jjroportion of carbon to 

 make steel. This discovery, followed by .Siemens's regenerative 

 furnace, by Whitworlh's compressed steel, and by the use of 

 alloys and by other improvements too numerous to mention here, 

 have revolutionised the conditions under which metals are 

 applied to engineering purposes. 



Indeed, few questions are of greater interest, or possess more 

 industrial importance, than those connected with metallic alloys. 

 This is especially true of those alloys which contain the rarer 

 metals ; and the extraordinary effects of small quantities of 

 chromium, nickel, tungsten and titanium on certain varieties of 

 steel have exerted profound influence on the manufacture of 

 projectiles and on the construction of our armoured ships. 



Of late years, investigations on the properties and structure of 

 alloys have been numerous, and among the more noteworthy 

 researches may be mentioned those of Dcwar and Fleming on 

 the distinctive behaviour, as regards the thermo-electric powers 

 and electrical resistance, of metals and alloys at the very low 

 temperatures which may be obtained by the use of liquid air. 



Prof Roberts-.Vusten, on the other hand, has carefully studied 

 the behaviour of alloys at verj- high temperat\ires, and by em- 

 ploying his delicate pyrometer has obtainetl phtitngraphic 

 curves which afford additional evidence as to the existence of 

 allotropic modifications of metals, and which have materially 

 strengthened the view that alloys are closely analogous to saline 

 solutions. In this connection it may be stated that the very 

 accurate work of Ilcycock and Neville on the lowering of the 

 solidifying ])oints of molten metals, which is caused by the 

 presence of other metals, affords a valuable contribution to our 

 knowledge. 



Prof. Roberts- .Austen has, moreover, shown that the effect of 

 any one constituent of an alloy upon the properties of the 

 principal metal has a direct relation to the atomic volumes, and 

 that it is consequently possible to foretell, in a great measure, 

 the effect of any given combination. 



A new branch of investigation, which deals with the micro- 

 structure of metals and alloys, is rapidly assuming much import- 

 ance. It was instituted by.Sorby in a communication which he 

 made to the British .Association in 1S64, and its development is 

 due to many patient workers, among whom M. Osmond occupies 

 a prominent place. 



.Metallurgical science has brought aluminium into use by 

 cheapening the process of its extraction ; and if by means of the 

 wasted forces in our rivers, or possibly of the wind, the extraction 

 be still further cheapened by the aid of electricity, vve may not 

 only utilise the metal or its alloys in increasing the spans of our 

 bridges, and in affording strength and lightness in the construc- 

 tion of our ships, but we may hope to obtain a material which 

 may render practicable the dreams of Icarus and of Maxim, and 

 for purposes of rapiti transit enable us to navigate the air. 



Long before 1S31 the steam-engine had been largely used on 



rivers and lakes, and for short sea passages, although the first 

 Atlantic steam-service was not established till 1838. 



As early as 1820 the steam-engine had been applied by 

 Gurney, Hancock, and others to road traction. The absuril 

 impediments placed in their way by road trustees, which, indeed, 

 are still enforced, checked any progress. But the question of 

 mechanical traction on ordinary roads was practically shelved ir» 

 1830, at the time of the formation of the British .Association, 

 when the locomotive engine was combined with a tubular boiler 

 and an iron road on the Liverpool and Manchester Railway. 



Great, however, as was the advance made by the locomotive 

 engine of Robert .Stephenson, these earlier engines were only 

 toys com]3ared with the comjjound engines of to-day which are 

 used for railw.ays, for ships, or for the manufacture of electricity. 

 Indeed, it may be .said that the study of the laws of heat, which 

 have led to the introduction of variotis forms of motive power, 

 are gradually revolutionising all our habits of life. 



The improvements in the production of iron, combined with 

 the developed steam-engine, have completely altered the con- 

 ditions of our commercial intercourse on land ; whilst the 

 changes caused by the effects of these improvements in ship- 

 building, and on the ocean carr)'ing trade, have been, if any- 

 thing, .still more marked. 



-At the foundation of the Association all ocean ships were built 

 by hand, of wood, propelled by .sails and manreuvred by manual 

 labour ; the material limited their length, which did not often 

 exceed 100 feet, and the number of English ships of over 500 

 tons burden was comparatively small. 



In the modern ships steam power takes the place of manual 

 labour. It rolls the plates of which the ship is constructed, 

 bends them to the required shape, cuts, drills, and rivets thent 

 in their place. It weighs the anchor ; it propels the ship in 

 spite of winds or currents ; it steers, ventilates, and lights the 

 ship when on the ocean. It takes the cargo on board and 

 discharges it on arrival. 



The use of iron favours the construction of ships of a large 

 size, of forms which afiVird small resistance to the water, and 

 with compartments which make the shii)s practically unsinkable 

 in heavy seas, or by collision. Their size, the economy with 

 which they are propelled, and the certainty of their arrival, 

 cheapens the cost of transport. 



The steam-engine, by comi>ressing air, gives us control over 

 the temjierature of cool chambers. In these not only fresh meat, 

 but the delicate produce of the -Antipodes, is brought across the 

 ocean to our doors without deterioration. 



Whilst railways have done much to alter the social conditions 

 of each individual nation, the application of iron and steam tO' 

 our ships is revolutionising the international commercial condi- 

 tions of the world ; and it is gradually changing the course of 

 our agriculture, as well as of our domestic life. 



But great as have been the developments of science ii> 

 promoting the connnerce of the world, science is asserting its 

 supremacy even to a greater extent in every department of war. 

 .And perhaps this ajjplication of science affords at a glance, better 

 than almost any other, a convenient illustration of the assistance 

 which the chemical, physical, and electrical sciences are affording 

 to the engineer. 



The reception of warlike stores is not now left to the uncertain 

 judgment of " practical men," but is confided to officers who 

 have received a special training in chemical analysis, and in the 

 application of physical and electrical science to the tests by 

 which the qualities of explosives, of guns, and of projectiles cai> 

 be ascertained. 



For instance, take explosives. Till quite recently black anil 

 brown powders alone were used, the former as old as civilisation, 

 the latter but a small modern imjirovement adapted to the 

 increased size of guns. Bui now the whole family of nitro- 

 cxplosives are rapidly superseding the old powder. These are 

 the direct outcome of chemical knowledge ; they are not mere 

 chance inventions, for every improvement is based on chemical 

 theories, and not on random experiment. 



The construction of guns is no longer a haphazard operation. 

 In spite of the enormous forces to be controlled and the sudden 

 violence of their action, the researches of the mathematici.an 

 have enabled the just proportions to be determined with accuracy ; 

 the labours of the physicist have revealed the internal con<litions 

 of the materials employed, and the best means of their favourable 

 employment. Take, for example, Longridge's coiMed-wire 

 system, in which each successive layer of which the gun is 

 formed receives the exact jjroportion of tension which enables 



NO. 1350. VOL. 52] 



