APPENDIX-GEOLOGICAL SURVEY. 399 
anything in the mineral kingdom connected with mineral veins 
that is not due either directly or indirectly to heat. 
Here too, as in the vegetable kingdom, we find certain con¬ 
ditions and forces uniting to produce certain results. And it 
is only when and where such conditions prevail, that such re¬ 
sults are obtained. The lines that mark the course and action 
of these forces are as legible in the crust of the earth, as the 
lines that mark the zones of productive vegetation on the 
surface. 
If we examine closely the physical conditions and forces of 
these two departments of nature, but few things will strike us 
with more force than the laws governing the absorption and 
radiation of heat. In the vegetable kingdom every tree, every 
plant, every flower, in fadt every organism seems to possess 
different absorbing and radiating powers, by which it is adapted 
to receive the warming, life-giving rays of the sun; indeed it 
presents one of the most refined systems of order and adapta¬ 
tion. And yet, this beautiful system is made to depend upon 
the amount of heat received from the sun, and upon the posi¬ 
tion of the earth in reference to the sun. 
No less distinct are the evidences of the relation of heat, 
and the laws governing its absorption and radiation to the va¬ 
ried forms of crystalline matter in the mineral kingdom. But 
i 
between the phenomena of heat in the vegetable kingdom, 
and the phenomena of heat in the mineral kingdom, there is a 
marked, indeed an essential, difference. This difference arises, 
no doubt, not from an essential difference in the physical char¬ 
acter of heat, but from an essential difference in the sources 
from whence it flows. We cannot fully comprehend the dif¬ 
ference between minerals and vegetables—both of which are 
the products of nature, formed out of similar material, heat 
being one of the elements of their conditions—until we regard 
the line that separates the vegetable and mineral kingdoms, as 
being the line that separates between the products of solar and 
terrestrial heat. The evidences of this are strong and convinc¬ 
ing, they appeal to our senses, and through them carry convic¬ 
tion to the mind. 
