September 12, 1895] 



NA TURE 



465 



and that tlie idea has been suggested that the various orders of 

 spectra of the same element are due to the existence of the ele- 

 ment in different molecular forms — allotropic or otherwise — at 

 different temperatures. 



But great as have been the advances of terrestrial chemistr)' 

 through its assistance, the most stupendous advance which we 

 owe to the spectroscope lies in the celestial direction. 



Astronomy. 



In the earlier part of this century, whilst the sidereal universe 

 was accessible to investigators, many problems outside the solar 

 system seemed to be unapproachable. 



At the third meeting of the Association, at Cambridge, in 

 1S33, Dr. Whewell said that astronomy is not only the queen of 

 science, init the only perfect science, which was " in so elevated 

 a state of flourishing maturity that all that remained was to de- 

 termine with the extreme of accuracy the consequences of its 

 rules by the profoundest combinations of mathematics ; the 

 magnitude of its data by the minutest scrupulousness of observa- 

 tion." 



But in the previous year, viz. 1S32, .■\iry, in his report to the 

 Association on the progress of ;ustronomy, had pointed out that 

 the observations of the planet Uranus could not be united in one 

 elliptic orbit ; a remark which turned the attention of Adams to 

 the discovery of Neptune. In his report on the position of 

 optical science in 1832, Brewster suggested that with the assist- 

 ance of .adequate instruments " it would be possible to study the 

 action of the elements of material bodies upon rays of artificial 

 light, and thereby to discover the analogies between their 

 affinities and those which produce the fixed lines in the spectra 

 of the stars ; and thus to study the effects of the combustions 

 which light up the suns of other systems." 



This idea has now been realised. All the stars which shine 

 brightly enough to impress an image of the spectrum upon a 

 photographic plate have been classified on a chemical basis. 

 The close connection between stars and nebula? has lieen demon- 

 strated ; and while on the one hand the modern science of 

 thermodj-namics has shown that the hypothesis of Kant and La- 

 place on stellar formation is no longer tenal)le, inquiry has indi- 

 cated that the true explanation of stellar evolution is to be found 

 in the gradual condensation of meteoritic particles, thus justifying 

 the suggestions put forward long ago by Lord Kelvin and Prof. 

 Tait. 



We now know that the spectra of many of the terrestrial ele- 

 ments in the chromosphere of the sun differ from those familiar 

 to us in our laboratories. We begin to glean the fact that the 

 chromospheric spectra are similar to those indicated by the ab- 

 sorption going on in the holiest stars, and Lockyer has not hesi- 

 tated to affirm that these facts would indicate that in those 

 localities we ar.; in the presence of the actions of temperatures 

 .sufficiently high to break up our chemical elements into finer 

 forms. Other students of these phenomena may not agree in 

 this view, and possibly the discrepancies may be due to det'ault 

 in our terrestrial chemistry. .Still, I would recall to you that 

 Dr. Carpenter, in his Presidential .\ddress at Brighton in 1S72, 

 almost censured the speculations of Frankland and Lockyer in 

 1868 for attributing a certain bright line in the spectrum of solar 

 prominences (which w.as not identifialile with that of any known 

 terrestrial source of lights to a hypothetical new substance which 

 they proposed to call " helium," because "it had not received 

 that verification which, in the case of Crookcs' .search for 

 tliallium, was afforded by the actual discovery of the new 

 metal." Ramsay has nov\* shown that this gas is present in 

 <iense minerals on earth ; but we have now also learned from 

 Lockyer that it ami other associated gases are not only found 

 with hydrogen in the solar chromosphere, but that these gases, 

 with hydrogen, form a large percentage of the atmospheric con- 

 stituents of some of the hottest stars in the heavens. 



The spectroscope has also made us acquainted with the 

 motions and even the velocities of those distant orbs which make 

 up the sidereal universe. It has enabled us to determine that 

 many stars, single to the eye, are really double, and many of the 

 conditions of these strange systems have been revealed. The 

 rale at which matter is moving in solar cyclones and winds is 

 now familiar lo us. And I may also add that quite recently this 

 wonderful instrument has enabled Prof Keeler lo verify Clerk 

 MaxwelTs theory thai the rings of Saturn consist of a marvellous 

 ctimjiany of separate moons— as it were, a cohort of courtiers 

 revolving round iheir queen — with velocities projjortioned to 

 /heir distances from the planet. 



NO. 1350, VOL. 52] 



Physics. 



If we turn to the sciences which are included under physics, 

 the progress has been equally marked. 



In optical science, in 1831, the theory of emi.s.sion as con- 

 trasted with the undulalory theory of light was still under 

 discussion. 



Young, who was the first to explain the phenomena due to the 

 interference of the rays of light as a consequence of the theory 

 of waves, and Fresnel, w ho showed the intensity of light for any 

 relative position of the interference-waves, both had only 

 recently passed away. 



The investigations into the laws which regulate the conduction 

 and radiation of heat, together with the doctrine of latent and of 

 specific heal, and the relations of vapour to air, had all tended to 

 the conception of a material heat, or caloric, communicated by 

 an actual flow and emission. 



It was not till 1S34 that imjjroved thermometrical appliances 

 had enabled Forbes and Melloni to establish the polarisation of 

 heat, and thus to lay the foundation of an undulalory theory 

 for heat similar to that which was in progress of acceptation for 

 light. 



Whewell's report, in 1832, on magnetism and electricity shows 

 that these branches of science were looked upon as cognate, and 

 that the theory of two opposite electric fluids was generally 

 accepted. 



In magnetism, the investigations of Ilansteen, Gauss, and 

 Weber in Europe, and the observations made under the 

 Imperial Academy of Russia over the vast extent of that 

 Empire, had established the existence of magnetic poles, and had 

 shown that magnetic disturbances were simultaneous at all the 

 stations of observation. 



At their third meeting the Association urged the Government 

 to establish magnetic and meteorological observatories in Great 

 Britain and her colonies and dependencies in different parts of 

 the earth, furnished with proper instruments, constructed on 

 uniform principles, and with provisions for continued observa- 

 tions at tho.se places. 



In 1839 the British Association had a large share in inducing 

 the Government to initiate the valuable .series of experiments for 

 determining the intensity, the declination, the dip, and the 

 periodical variations of the magnetic needle which were carried 

 on for several years, at numerous selected stations over the 

 surface of the globe, under the directions of Sabine and Lefroy. 



In England systematic and regular observations are still made 

 at Greenwich, Kew, and Slonyhurst. For some years past 

 similar observations Ijy both absolute and self-recording instru- 

 ments have also been made at Falmouth — close to the home of 

 Robert Were Fox, whose name is inseparably connected with 

 the early history of terrestrial magnetism in this country — but 

 under such great financial difficulties that the continuance of the 

 work is seriously jeopardised. It is lo be hoped that means 

 may be forthcoming to carry it on. Cornishmen, indeed, could 

 found no more fitting memorial of their distinguished country- 

 man, John Couch .Adams, than by suitably endowing the mag- 

 netic observatory in which he took so lively an interest. 



Far more extended oliservation will be needed before we can 

 hope to have an established theory as to the magnetism of the 

 earth. We are without magnetic observations over a large part 

 of the southern hemisphere. And Prof. RUcker's recent investi- 

 gations tell us that the earth seems as it were alive with m^- 

 netic forces, be they due to electric currents or to variations in 

 the slate of magnetised mailer ; that the disturbances afiect not 

 only the diurnal movement of the magnet, but that even the 

 small part of the secular change which has been observed, and 

 which has taken centuries to accomplish, is interfered with by 

 some slower agency. .Vnd, what is more important, he tells us 

 that none of these observations stand as yet upon a firm basis, 

 because standard instruments have not been in accord : and 

 much labour, beyond the power of individual efibrl, has hitherto 

 been required lo ascertain whether the relations between them 

 are constant or variable. 



In electricity, in 1 831, just at the time when the British 

 Association was founded, Faraday's splendid researches in 

 electricity and magnetism at the Royal Institution had begun 

 with his discovery of magneto-electric induction, his investiga- 

 tion of the laws of electrochemical decomposition, and of the 

 mode of electrolylical action. 



But the practical application of our electrical knowledge was 

 then limited to the use of lightning-conductors for buildings and 

 ships. Indeed, it may be said thai the applications of elec- 



