Geography of the Land. 47 
description of the famed district around Asheville, North Caro- 
lina. These have a substantial interest to us, treating as they do 
of localities so well known ; and they illustrate, too, the resources 
of induction in bringing to our view the probable wonders of 
ancient geographic forms. 
The constitution of the interior of the earth is a subject of 
great interest in the science of geography, as many of the visible 
forms upon the crust have been wrought by the power of the 
agencies within it. The discussion has been warm in the past, 
and doubtless will be resumed with unabated interest as we find 
new phenomena for the argument. The apparent lull that has 
followed the promulgation of the theory, three years ago, that 
under the crust we should find a fluid, or semi-fluid, surrounding 
a solid nucleus, may not be of long duration. This hypothesis 
probably comes nearer to satisfying the conditions imposed by the 
physicist and geologist, than those which have preceded it, and 
may be accepted for the present ; unless the processes of nature 
by which it is conceived this state of the interior of the earth 
has been produced, shall be demonstrated to have continued for 
sufficient time to have caused a condition of equilibrium and possi- 
ble solidification of the whole sphere ; when we might expect it 
to be repudiated by those who oppose the theory of isostacy, but 
commended by the physicists as supporting their claim that the 
earth must be substantially a solid even now. If we accept Mr. 
Frederick Wright’s suggestion, isostacy may have an important 
bearing on the cause of the ice sheets that covered such great 
areas ; a suggestion that opens to the vision of the imagination 
an orography beside which the grandest landscape we may see 
to-day would pale into insignificance. This is believed to bea 
new application of the isostatic theory, and may be a possible 
solution of a much vexed question when an initial cause for such 
great upheavals can be advanced that will not be inconsistent 
with other accepted conditions. 
Theories are modified by new facts, and in any attempt to 
demonstrate the constitution of the interior of the earth, the 
increase of temperature with the depth is an important factor. 
The recent measures, therefcre, in Germany, that indicate the 
figures generally accepted are not reliable, may be received with 
interest. The shaft was sunk especially for the purpose of ob- 
serving temperatures at different depths, and every precaution 
that former experience had suggested seems to have been taken 
