260 LOWELL— REPULSION OE GASEOUS ^MOLECULES. [April 21, 



at this inopportune moment he would naturally conclude that no 

 repulsion existed while in truth another motion was temporarily 

 obstructing it. 



7. Lastly the spectrograms and spectroscopic observations of 

 Frost and Parkhurst. de la Baume Pluvinel and Baldet agree in 

 showing the light of the tail of Morehouse's comet to have been 

 due practically wholly to emission ; in other words to glowing gas. 

 Here, then, we have not only corroboration of the fact, brought 

 forward from study of Halley's comet, to wit : that molecules of gas 

 are repelled by the sun, but, from the light of the tail being com- 

 posed solely of gaseous molecules, any supposition that they were 

 not the cause of the visible effect, is entirely excluded. 



We reach then this interesting conclusion: that molecules of gas 



not only may be but demonstratedly are repelled by the action of 



the sun and that though we have reason to suppose that minute solid 



particles may be similarly impressed it is of the former not the latter 



that we have direct proof at present. 



Lowell Observatory, 

 April 10, 191 1. 



