ADDRESS. XCIX 



comparisons between the positions of the dark lines in the prismatic spectrum 

 and in his own " interference spectrum " (produced by substituting for the 

 prism a fine grating). A first comparatively rough application of the test by 

 Miller and Huggins to a large number of the principal stars of our skies, 

 including Aldcbaran, a Ononis, ft Pegasi, Sirius, n Lyras, CapeUa, Arcturus, 

 Pollux, Castor (which they had observed rather for the chemical purpose than 

 for this), proved that not one of them had so great a velocity as 315 kilometres 

 per second to or from the earth, which is a most momentous result in respect 

 to cosmical dynamics. Afterwards Huggins made special observations of 

 the velocity test, and succeeded in making the measurement in one case, 

 that of Sirius, which he then found to be receding from the earth at the rate 

 of G(j kilometres per second. This, corrected for the velocity of the earth at 

 the time of the observation, gave a velocity of Sirius, relatively to the Sun, 

 amounting to 47 kilometres per second. The minuteness of the difference to 

 be measured, and the smallness of the amount of light, even when the brightest 

 star is observed, renders the observation extremely difficult. Still, with 

 such great skill as Mr. Huggins has brought to bear on the investigation, 

 it can scarcely be doubted that velocities of many other stars may be 

 measured. "What is now wanted is, certainly not greater skill, perhaps not 

 even more 2}owerful instruments, but more instruments and more ohservers. 

 Lockyer's applications of the velocity test to the relative motions of different 

 gases in the Sun's photosphere, spots, chromosjihere, and chromosphcric pro- 

 minences, and his observations of the varying spectra presented by the same 

 substance as it moves from one position to another in the Sun's atmosphere, 

 and his interpretations of these observations, according to the laboratory 

 results of Frankland and himself, go far towards confirming the conviction 

 that in a few years all the marvels of tlie Sun will be dynamically explained 

 according to known properties of matter. 



During six or eight precious minutes of time, spectroscopes have been ap- 

 plied to the solar atmosphere and to the corona seen round the dark disk of 

 the Moon eclipsing the Sun. Some of the wonderful results of such obser- 

 vations, made in India on the occasion of the eclipse of August 1808, were 

 described by Professor Stokes in a previous address. Yaluablo results have, 

 through tlie liberal assistance given by the British and American Govern- 

 ments, been obtained also from the total eclipse of last December, notwith- 

 standing a generally unfavourable condition of weather. It seems to have 

 been proved that at least some sensible part of the light of the "corona" is a 

 terrestrial atmospheric halo or dispersive reflection of the light of the glow- 

 ing hydrogen and " helium"* round the sun. I believe I may say, on the 

 present occasion when preparation must again be made to iitilize a total 

 eclipse of the Sun, that the British Association confidently trusts to our 

 Government exercising the same wise liberality as heretofore in the interests 

 of science. 



The old nebular hypothesis supposes the solar system, and other similar 

 systems through the universe which we see at a distance as stars, to have 

 originated in the condensation of fiery nebulous matter. This hypothesis 

 was invented before the discovery of thermo-dynamics, or the nebulic v\'ould 

 not have been supposed to be fiery ; and the idea seems never to have 

 occurred to any of its inventors or early supporters that the matter, the con- 

 densation of Avhich they supposed to constitute the Sun and stars, could have 



* Frankland and Loekyer find the yellow prominences to giire a very decided bright line 

 not far from D, but liitherto not identified with any terrestrial flame. It seema to indicate 

 a new substance, wliieh they propose to call Helium. 



