ANNIVERSARY ADDRESS OF THE PRESIDENT, IxXUl 



eifected or accompanied by either paroxysmal or gradual and uniform 

 action of the forces which have modified the earth's surface. Ey 

 non-progression I understand, not the absence of periodically recur- 

 ring changes, but of that permane7it change above mentioned. The 

 periodical changes in this case, equally with the permanent changes 

 of the former case, may have been produced or accompanied by either 

 paroxysmal or uniform action. The theory of non-progression is 

 essentially different from the theory of uniformity ; and thus while 

 we might allow the justice of the appeal to the xilps, made by my 

 distinguished predecessor in this chair, in proof of non-progression as 

 indicated by an apparent equality of intensity in the more recent and 

 the more remote geological action, we might reject the appeal if made 

 to prove that the forces which elevated the x\lps were of no greater in- 

 tensity than those which have been in action during the historic period. 

 It is not then, I conceive, to the phsenomena of elevation, or of 

 denudation and deposition, as indicating more or less of paroxysmal 

 or tranquil action, that we must look for any demonstrative evidence 

 to decide the question before us. But there is one most important 

 agent which has doubtless been most active, not only in producing 

 the phsenomena of elevation, but also in modifying the characters of 

 the inorganic matter composing the crust of the globe, and it is ex- 

 tremely difficult to conceive how the activity of that agent can have 

 consisted with non-progression. The agent I speak of is heat. I 

 assume the truth of the simple proposition, that Jf a mass of matter^ 

 such, for instance, as the earth with its waters and its atmosphere, 

 he placed in space of which the temperature is lower than its own, 

 it will necessarily lose a portion of its heat hy radiation, until its 

 temperature ultimately approximates to that of the circumambient 

 space, unless this reduction of temperature be prevented by the con- 

 tinued generation of heat. If there be any propositions in experi- 

 mental science which may be deemed incontrovertible, this, I con- 

 ceive, is one of them. Now we know that the interior temperature 

 of the earth is higher than that of its surface ; and, in order that 

 this state of terrestrial temperature may be consistent with non-pro- 

 gression, it must either be a permanent state, or must belong to a 

 series of changes recurring periodically, but producing no permanent 

 change or progression from a higher primitive to a lower ultimate 

 temperature. If the present temperature be permanent, it must be 

 maintained by some cause constantly acting within the earth and 

 generating a quantity of heat exactly equal to that which is lost by 

 radiation into surrounding space. No external cause, such as solar 

 or stellar radiation, could produce an absolutely constant, stationary 

 temperature, which should increase in descending beneath the earth's 

 surface. Chemical action might produce this effect, possibly, for a 

 finite time, but philosophers, I imagine, would no more believe that 

 or any other internal cause capable of producing such an effect for 

 an infinite time, than they would believe in perpetual motion, in the 

 ordinary sense of the expression. I cannot conceive, therefore, the 

 present state of terrestrial temperature to be ^permanent state. Can 

 it belong to a perpetually recurring series of changes? I would 



