Sept. I, 1881] 



NA TURE 



4H 



fubsequeiilly attacked the problem from the other .-ide, and 

 showed that if all the heat passing through a steam-engine was 

 turned into work, for every degree Fahr. added to the tempera- 

 ture of a pound of water, enough work could be done to raise a 

 weight of I lb. to a height of 772 feet. The general result is 

 that, though we cannot create energy, we may help ourselves to 

 any extent from the great storehouse of nature. Wind and 

 water, the coal-bed and the forest, afford man an inexhaustible 

 supply of available energy. 



It used to be considered that there was an absolute break 

 between the difterent states of matter. The continuity of the 

 gaseous, liquid, and solid conditions was first demonstrated by 

 Andrews in 1862. 



Oxygen and nitrogen have been liquefied independently and 

 at the same time by Cailletet and Raoul Pictet. Cailletet also 

 succeeded in liquefying air, and soon afterwards hydrogen was 

 liquefied by Pictet under a pressure of 650 atmospheres, and a 

 cold of 170° Cent, below zero. It even became | artly solidified, 

 and he assures us that it fell on the floor with "the shrill noise 

 of metallic hail." Thus then it was shown experimentally that 

 there are no such things as absolutely permanent gases. 



The kinetic theory of gases, now generally accepted, refers 

 the elasticity of gases to a motion of translation of their mole- 

 cules, and we are assured that in the case of hydrogen at a 

 temperature of 60° Fahr. they move at an average ra'e of 6225 

 feet in a second ; while as regards their size, Loschmidt, who 

 has i-ince been confirmed by Stoney and Sir W. Thomson, 

 calculates that each is at most I -50000000th of an inch in 

 diameter. 



We cannot, it would seem at present, hope for any increase of 

 our knowledge of atoms by any improvement in the micro- cope. 

 With our present instruments we can perceive lines ruled on glass 

 of I -90,000th of an inch apart. But, owing to the properties of 

 light itself, the fringes due to interference begin to produce 

 confusion at distances of 1-74,000. It would seem then that, 

 owing to the physical characters of light, we can, as Sorby has 

 pointed out, scarcely hope for any great improvement so far as 

 the mere visibility of structure is concerned, though in other 

 respects no doubt much may be hoped for. At the same time, 

 Dallinger and Royst^n Pigott have >hown that, so far as the mere 

 presence of simple objects is concerned, bodies of even smaller 

 dimensions can be perceived. 



Sorby is of opiniin that in a lengih of l-8o,cooth of an inch 

 there would probably be from 500 to 2000 molecules — 500, for 

 instance, in albumen and 20CO in water. Even, then, if we could 

 construct microscopes far mere powerful than any we now possess, 

 they would not enable us to obtain by direct vision any idea of 

 the ultimate mol-jcules of matter. Sorby calculates that the 

 smalle-t sphere of organic matter which could be clearly defined 

 with our most powerful microscopes woald contain many 

 millions of molecules of albumen and water, and it follows 

 that there may be an alm.ost infinite number of structural charac- 

 ters in organic tissues, which we can at present foresee no mode 

 of examining. 



Electricity in the year 1831 may be considered to have just 

 been ripe for its adaptation to pi-actical purposes ; it was but a 

 few years previously, in 1819, that Oersted had discovered the 

 deflective action of the current on the magnetic needle, that 

 Ampere h.ad laid the foundation of electro-dynamics, that 

 Schweizzer h.id devised the electric coil or multiplier, and that 

 Sturgeon had constructed the first electro-magnet. It was in 

 1831 that Faraday, the piince of pure experimentalists, an- 

 nounced hLs discoveries of voltaic induction and magneto- 

 electricity, which with the other three discoveries constitute the 

 principles of nearly all the telegraph instruments now in use ; 

 and in 1834 our knowledge of the nature of the electric current 

 had been much advanced by the interesting experiment of Sir 

 Charles Wheat- tone, proving the velocity of the current in a 

 metallic conductor to approach that of the wave of light. 



Practical applications of these discoveries were not long in 

 coining to the fore, and the first telegraph line on the Great 

 Western Railway from Paddington to West Drayton was set 

 up in 1S3S. In America Morse is said to have commenced 

 to develop his recording instrument between the years 1832 

 and 1837. 



In 1 85 1, submarine telegraphy became an accomplished fact 

 through the successful establishment of telegraphic communica- 

 tion between Dover and Calais. Submarine lines followed in 

 rapid succession, crossing the English Channel and the Geiman 

 Ocean, threading their way through the Mediterranean, Black 



and Red Seas, until in 1866, after two ab jrtive attempts 

 telegraphic communication was successfully established between 

 the Old and New Worlds, beneath the Atlantic Ocean. 



Duplex and quadruplex telegraphy, one of the most striking 

 achievements of modern telegraphy, the result of the labours of 

 several inventors, should not be passed over in silence. It not 

 only serves for the simultanecus communication of telegraphic 

 intelligence in both directions, but renders it possible for four 

 instruments to be wcrked irrespectively of one another, through 

 one and the same wire connecting to distant places. 



Another more recent and perhaps still more wonderful^ 

 achievement in modern telegraphy is the inventi-^n of the 

 telephone and microphone, by means of which the human voice 

 is transmitted through the electric conductor, by mechanism that 

 imposes through its extreme simplicity. In this connection the 

 names of Reiss, Graham Bell, Edison, and Hughes are those 

 chiefly deserving to he recorded. 



By the electric transmission of power, we may hope some day 

 to utilise at a distance such n.atural sources of energy as the Falls 

 of Niagara, and to work our cranes, lifts, and machinery of 

 every descripiinn by means of smrces of power arranged at con- 

 venient centres. To these ai plications the brothers Siemens 

 have more recently added the propulion of trains by currents 

 passing through the rails, the fusion in considerable quantities of 

 highly refractoi7 substances, and the use of e'ectric centres of 

 light in horticulture as proposed by Werner ard William Siemens. 

 By an es-ential imorovement by Faure of the Plantc Secondary 

 Ba'tery, the problem of storing electrical energy appears to 

 have received a practical solution, the real importance of which 

 is clearly proved by Sir W. Thomion's recent investigation cf 

 the subject 



It would be difficult to assign the limits to which this develop- 

 ment of electrical etiergy may not be rendered serviceable for 

 the purposes of man. 



As regards Mathematics I have felt that it would be impossible 

 for me, ei'en with the kindest help, to write anything myself. 

 Mr. Spoltiswoode, however, has been so good as to supply rae 

 with the follow irg memorandum. 



In a complete survey of the progress of science during the half- 

 century which has intervened between our first and cur present 

 meeting, the part played by mathematics would form no in.sig- 

 nificairt feature. To those indeed who are outside its enchanted 

 circle it is difficult to realise the intense intellectual energy which 

 actuates its devotee*, or the wide expanse over which that energy 

 ranges. 



In the extension of mathematics it has happened more than 

 once that laws have been establi.-.hed so simple in firm, and so 

 obvious in their neces?ity, as scarcely to require proof. And yet 

 their application is often of the highest importance in checking 

 conclusions which have b.een drawn from other considerations, 

 as well as in leading to conclusions which, without their aid, 

 might have been difiicult of attainment. The same thing has 

 occurred also in physics ; and notably in the recognition of what 

 has been termed the " Law of the Conservation of Energy." 



Energy has been defined to be " The capacity, or power, ot 

 any body, cr system of bodies, when in a given condition, to do 

 a measurable quantity of work." Such work may either change 

 the condition of the bodies in question, or it may affect other 

 bodies ; but in either case energy is expended by the agent upon 

 the recipient in performance cf the work. The law then states 

 that the total amount of energy in the agents .and recipients taken 

 together remains unaltered by the changes in question. 



Now the principle on which the law depends is this: "that 

 every kind of change amrng the bodies u'ay be expressed nu- 

 merically in one standard unit of change," viz., work done, in 

 such wi-e that the residt of the passage of any system from one 

 conlition to another may be calculated by mere additions and 

 subtractions, even when we do not know how the change came 

 about. 



The history of a discover)', or invention, so simple at fir-t 

 sight, is often found to be more complicated the more thoroughly 

 it is examined. That which at first seems to have been due to 

 a single mind proves to have been the result of the successive 

 action of many minds. Attempts more or less successful in the 

 sa-m' direction are frequently traced cut ; and even unsuccessful 

 efforts may not have been without influence on minds turned 

 towards the same object. Lastly also, germs of thought, origin- 

 ally not fully understood, sometimes prove in the end to have 

 been the first stages of growth towards ultimate fruit. The 

 histery of the law of the conservation of energy forms no 



