— a 
' SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 67 
just shown, the surface of v’ is only one-fourth that of v. There- 
fore, asa 4 times greater force will be exerted on a 4 times 
smaller surface, on a unit of surface the force or pressure on v’ is 
16 times the former pressureon v. That is, p’ = 16p. 
Morover, Mariotte’s well-known law requ'res that for a body 
of gas: The products of its volume and pressure changes as 
its temperature changes. 
, 
lelSmOS, Wes os Ol sea) 28 UG 
ON, GPP PND WOES & 0% 
Of, mens 2 Seydesely 
or) 127. 
’ 
Thus, when contracted to half its radius the globe of gas is 
twice as hot as at the outset. In general, as it radiates heat 
it contracts, and as it contracts it grows hotter. 
If, then, our Sun is truly gaseous from center to surface, 
notwithstanding its vast output of heat it must, by contraction, 
eontinually grow hotter. If however, as is lkely, the photo- 
sphere of incandescent clouds of carbon droplets and the cen- 
tral density have made it partly viscous, or partly liquid or 
even semi-fluid, then the heat produced by contraction may 
just equal that lost by radiation. In this case, ‘the Sun’s tem- 
perature will be constant—as probably it has been during the 
historic past. 
With increased condensation, the heat of contraction will 
fail to replace that lost by radiation, and the Sun’s temperature 
will lower more until it becomes cold, solid, dark! 
When by contraction its present diameter is reduced one- 
half, its density will be increased eight-fold. It will doubtless 
be non-gaseous and will be cooling. Contracting still, cooling 
more, radiating less and less heat, it must finally fail to sup- 
port any of the present forms of terrestrial life—the world we 
know will be dead! 
It is somewhat comfortine to learn from Neweomb and 
other eminent authorities that ‘this had failure of our now 
glorious Day-Star, when its generous heat and light shall be 
quenched—our world’s night of death—is probably distant in 
the future some ten million years! 
“Flora of Clifton, Arizona 
ASCLEPIADACE. 
Philabertia cynanchoides, Gray. Common. July. 
Asclepias mexicana, Cay. Dunean. July. 
