{ 
186 Wixtson—On the Temperature of certain Stars. 
any light coming from the gaseous layers below, and also so deep that the elements, 
which in the Sun are carried by convection-currents above the photosphere, and 
give us the Fraunhofer spectrum, would be unable to rise to that altitude. Thus, 
only elements lke hydrogen, with an atomic weight less than carbon, would be 
able to draw their dark lines across his brilliant continuous spectrum. As the Sun 
seems to be so near the critical temperature at which the photospheric clouds are 
vaporized, it seems likely that Sirius is at a slightly lower temperature than the 
Sun, a temperature at which the star’s photosphere is of great depth and stability. 
It seems, therefore, most probable that [V-type stars are at a higher tempera- 
ture than the Sun, and that Sirian stars owe their great brilliancy, not to very 
high temperature, but because their photosphere is a deep one, and its continuous 
spectrum is not darkened by the numerous lines, especially in the ultra-violet, 
which we have in the solar type of stars. 
