182 POPULAR LECTURES AND ADDRESSES. 



than for this), proved that not one of them had so 

 great a velocity as 3 1 5 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 66 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 powerful instruments, but more instru- 

 ments and more observers. Lockycr's applications 

 of the velocity test to the relative motions of 



