68 



NA TURE 



[May 1 8. 1893 



the existence of the luminiferous ether, even though the pro- 

 foundest thinkers and most successful workers of the present 

 day may have all the conviction of Lord Kelvin, who has 

 declared that "it is the only substance that we are confident of 

 in dynamics, the one thing we are sure of is the reality and 

 substantiality of the luminiferous ether ! " 



But what has the Engineer to do with such speculations, and 

 what does it matter to him how light and heat are transmitted 

 from the sun or from the stars, or by what mechanism heat, 

 magnetism, and electricity are diffused over the earth ? This 

 question is being answered already in our daily practice, and 

 is destined, no doubt, to receive fuller and more convincing 

 response as time rolls on. I will give one or two instances. The 

 study of the spectrum produced by the passage of light through 

 triangular prisms has revealed the fact that the ordinary rays of 

 white light are of a complex nature, that only a portion of them 

 are discernible directly by the sense of sight or by that of feel- 

 ing, while the ultra-violet rays can only be seen in their action 

 on Uranium glass, or in the chemical decomposition they pro- 

 duce in certain substances. But, further, the specirum viewed 

 by modern instruments is found not to be continuous ; it is 

 crossed by dark, by light, and by coloured bands, which the 

 patient researches of Fraunhofer, Kirchhoff, Huggins, Norman 

 Lockyer, and others, have shown by their position, thickness, 

 or colour to characterise certain glowing substances, and by com- 

 parison with the spectra produced by heated terrestrial solids and 

 gases, it has been proved that many of the elements in the sun 

 and in the stars are identical with those with which we are 

 familiar on this earth, and this knowledge has served in a strik- 

 ing manner to confirm the correctness of the nebular theory as to 

 the origin of our planetary system. 



Not only have a large number of terrestrial elements been 

 discovered in the sun, but the spectroscope has revealed, to a 

 large extent, the order in which they are arranged on the sun's 

 surface, and this leads to the conclusion that at one time a similar 

 order prevailed on the earth, and therefore throws some light on 

 the deep geology of our planet. 



One ot the practical outcomes of these discoveries has been 

 the theory of Mendeleeff on the origin of petroleum, a theory of 

 the utmost importance to the human race, and to our country in 

 particular, in view of the inevitable exhaustion of our coal 

 supplies, for it asserts that petroleum is the product of the action 

 of water on the carbides of metals at high temperatures at no 

 very great relative depths in the crust of the earth, that this pro- 

 duction is continually in progress, and that deposits thus actually 

 forming may be reached in many places by sufficiently deep 

 borings ; and in view of recent progress in mechanical skill, it 

 certainly would be rash to say that borings of immensely greater 

 depth than any that we are as yet acquainted with will never be 

 made, for if accumulated evidence as to the correctness of 

 MendeleefTs views together with the ever-increasing cost of fuel, 

 shall hold out hopes of success, enterprising men will be found 

 ready to embark their means in undertakings, the risks of which 

 would not seem to be more formidable than those which sur- 

 rounded the laying of the first Atlantic telegraph cable, and 

 the rewards of success in which would be incomparably greater. 



The researches of Roberts- Austen, of Osmond, Le Chatelier, 

 and others, are slowly, but it is hoped surely, establishing laws 

 by which the relative atomic volumes of ingredients will become 

 a guide to the nature of their mutual interaction, and it seems 

 probable that spectrum observations which are of such value in 

 gauging the purity of the materials dealt with, will come in 

 aid and in support of the indications given by automatically 

 traced curves of rates of cooling, which have given such a 

 deep meaning to the phenomenon of recalescence, a property of 

 iron and steel which lor many years remained a mere laboratory 

 curiosity. 



Many bodies, including metals and their alloys, may exist in 

 more than one form ; sulphur, for example, assumes two allo- 

 tropic states, but at ordinary temperatures and in a com- 

 paratively short time the one condition passes into the other 

 Mr, Addenbrook has recently prepared an alloy of aluminium, 

 and nickel, which when freshly made possesses considerable 

 tenacity, but which, after a few hours, crumbles into powder. 

 The researches of Osmond seem to show that pure iron also 

 can exist in two states — one very hard, the other soft, and it is 

 more than probable that these states merge into each other 

 under certain conditions of heating or cooling, or under the 

 influence of foreign substances. There can be no doubt that 

 steel also, in course of time, undergoes molecular change at 



NO. 1229, VOL. 48] 



ordinary temperatures, and possibly under the influence of 

 strains produced by internal stresses due to unequal rates of 

 cooling. It is a common opinion, based on experience, that 

 tool steel should not be used as freshly made, but should be 

 kept some months, and the same precaution applies to dies 

 used in coining and similar operations, and to armour-piercing 

 shot, both of which, having been hardened by necessarily un- 

 equal and rapid cooling, either accommodate themselves to the « 

 stresses engendered by slow changes in the motion of the mole- J 

 cules, or fail spontaneously even after months of repose. Glass 

 undergoes similar changes, and generally materials which have 

 been severely strained either by the external application of force, 

 or by heating, will only gradually recover their normal con- 

 dition. This has been beautifully demonstrated by Prof. 

 Hughes, with the aid of his induction balance, on specimens of 

 the narrow steel ribbon used in the manufacture of Longridge 

 wire gims. A number of specimens recently submitted to him 

 showed a remarkable uniformity of structure, but when heated 

 to only 100° and examined immediately on cooling to the 

 normal temperature, a distinct change was observable, yet after 

 a few hours' rest the material returned to its normal state. If 

 such changes are measurable in ribbon \ in. x ,'j in. in cross 

 section, what may not be the molecular conflict in large masses ?' 

 These may be produced by alternations of stresses as well as 

 by changes of temperature, and point to the necessity of assist- 

 ing the molecules and atoms to adjust themselves, or to return 

 to a normal condition by raising the temperature of the sub- 

 stance to about the point indicated by h on Chernofi's scaler 

 below which no change in the nature of crystallisation t.ikes 

 place, no matter how slowly the mass is allowed to cool. This 

 principle is recognised in many ways in the arts. In drawing 

 wire or in solid drawn metal-work, such as tubes and cartridge- 

 cases periodical annealing must be resorted to ; moreover, experi- 

 ence has shown that crane-chains, for example, should be 

 annealed from time to time if they are to be used with safety ; 

 and Mr. Webb has adopted, with the best results, the plan of 

 treating in a similar manner the moving parts of his locomotives 

 after they have run a certain number of miles. 



I feel convinced that the frequent disasters with screw pro- 

 peller shafts, especially after they have been some time in use, 

 arise from the failure to recognise the practical bearing of the 

 tendency to molecular change under the influence of strain and 

 temperature. A propeller shaft is subject to constant varia- 

 tions of stress due to the action of the cranks of the engine, to 

 similar variations caused by the inertia of the screw, and a|;ain 

 to a totally dift'erent set of stresses which may often be alter- 

 nately tensile and compressive, due to the wear of the journals 

 and to the working of the hull. The remedy, I feel convinced, 

 lies in the periodical annealing of the material which must of 

 necessity be so hardly used. 



I think that it is now generally acknowledged that the lum- 

 iniferous ether is also the medium by which electrical energy is 

 transmitted by some kind of vibratory motion ; hence the ease 

 with which heat or mechanical work is transformed directly 

 into electric currents in the thermopile, or in the frictional elec- 

 trical machine, and the reasonableness of the great generalisa- 

 tion that we are living on a huge magnet — the poles of which 

 are not far from coinciding with the poles of the earth. 



Any one who doubts the value of abstract science should study 

 the construction of the mariners' compass, and especially in the 

 improved form introduced by Lord Kelvin ; let him compare 

 the blind groping after correction for the local attraction of the 

 ;ship with the beautiful and simple theory which has rendered' 

 ; that correction not only easy but readily adapted to changes in 

 the ship's position in the world ; he will find that there is not 

 a more striking instance of the profoundest abstract knowledge 

 blended with the power to turn it to practical use, than in this 

 and in so many other labours of the distinguished man whom t 

 have named more than once, and whom this institution is proud 

 to number among its honorary members. 



I would now draw your attention to a startling consequence 

 of the undulatory theory in the power which exists of exercising 

 influence, by what is termed induction, at great distances. 

 Animated by the conviction that electric energy was transmitted 

 in the same manner and by means of the same all-pervading 

 medium as radiant energy, and that the distance to which its 

 eflects would reach should be unlimited, though the apprecia- 

 tion might be a question of the delicacy of instruments, Mr. 

 Preece has succeeded in sending messages by Morse signals 

 across the Bristol Channel between Lavernock and Flatholme^ 



