136 THE CANADIAN NATURALIST. [Vol. vi. 



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 mo^t momentous result in o^esjyect to cosmical 

 ch/namics. 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 6G 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 kilo- 

 metres per second. The minuteness of the difference to be 

 measured, and the smalluess 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 velo- 

 cities of many other stars may be measured. What is now wanted 

 is, certainly not greater skill, perhaps not even more powerful in- 

 struments, but more instruments and more observers. Lockyer's 

 applications of the velocity test to the relative motions of different 

 gases in the Sun's photosphere, spots, chromosphere, and chro- 

 mospheric prominences, and his observations of the varying spec- 

 tra 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 Frank- 

 land and himself, "o far towards conj&rmino; the conviction that 

 in a few years all the marvels of the sun will be dynamically ex- 

 plained according to known properties of matter. 



4. SOURCE OF THE SUN'S HEAT. 



During six or eight precious minutes of time, spectroscopes 

 have been applied to the solar atmosphere and to the corona seen 

 round the dark disc of the Moon eclipsing the Sun. Some of the 

 wonderful results of such observations, made in India on the 

 occasion of the eclipse in August, 1868, were described by Prof. 

 Stokes in a previous address. Valuable results have, through the 

 liberal assistance given by the British and American Governments, 

 been obtained also from the total eclipse of last December, not- 

 withstanding a generally unfavourable condition of weather. It 

 <eems to have been proved that at least some sensible part of the 

 light of the ''"corona" is a terrestrial atmospheric halo or disper- 

 sive reflexion of the lii^ht of the dowinu' hydroi>en and " helium " 



