ADDRESS OF PROFESSOR LOVERING. 643 
theory to color, few astronomers will be willing to follow Doppler 
in all his extravagancies. 
If it be true, theoretically, that the relative velocity of light, 
the wave-length of transmission, and the period of oscillation in 
the ether, are altered by the relative motion of the observer and 
the place from which the undulation starts, it is obvious that all 
other velocities have but a small chance in competition with the 
velocity of light, and that slight changes of color, if physically 
real as Doppler supposed, would fail of being recognized even by 
the eye of a painter. To interpose the spectroscope, and observe 
the change of refrangibility by the displacement of the sharp lines 
of the spectrum, was a lucky escape from this embarrassment. 
After Huggins had tried his hand at this new method, with a 
small telescope, upon the brightest of all the stars, he was sup- 
plied by the Royal Society of London with a larger instrument 
to pursue the investigation. The results of his spectroscopic in- 
quiry into the motions of many stars have been published. Where 
these results have conflicted with the foregone conclusions of as- 
tronomy, Huggins has not hesitated to arraign the accuracy of 
astronomical data and methods. I have freely admitted the deli- 
cacy and difficulty of the geometrical process. The spectroscopic 
analysis, when applied to the same problem, walks upon slippery 
ground and must take heed lest it also fall. The alleged dis- 
Placement is a nice quantity, and instrumental sources of error 
Mave been pointed out which may explain away the whole of it. 
I lay no stress upon the large difference between Vogel and 
Huggins in the quantity of motion which spectrum analysis 
ascribes to Sirius, inasmuch as the direction of the motion is the 
Sine. We do not yet know all the elements*which the earth 
_ Contains. The spectroscope has already added four to the 
_ ‘Mmber, There is reason to think that the stars, though having 
some Substances in common with the earth and sun, are not 
without their peculiarities, The lines in the stellar spectra may 
i hag of position, not because they are the displaced lines of 
. _ » Magnesium, and hydrogen, but in consequence of novel- 
2 JA In the gaseous atmospheres of the stars. Still, there will be 
| Presumption, perhaps a probability, in favor of Huggins’ deduc- 
m, ir it rest on a sound basis of theory. If there is any weak- 
2 ay im the physical and mathematical foundation of his argument, 
