132 Proceedings of the Royal Physical Society. 
I. Deductions from the Hypothesis of the Internal Fluidity of the Earth. 
By William Stevenson, Esq., Dunse. Communicated by George 
Logan, Esq., W.S. 
It is now all but universally admitted by geologists, that 
the globe which we inhabit was, at a certain remote period, 
in a state of complete fusion through intense heat, and that 
from this state it has been gradually cooled down to its 
present temperature by the process of radiation of its surface 
heat into space. The object of this paper is to show a 
few of the results flowing from these premises, assumed 
to be correct ; — certain postulates being further granted 
of a character as nearly approaching the truth as the 
present imperfect state of our knowledge regarding the 
subject will admit. 
1. It has been well ascertained that, in descending into 
the interior of our globe, after passing through the stratum 
affected by the solar radiation (which nowhere appears 
greatly to exceed 100 feet), a gradual increase of tempera- 
ture is experienced, owing to the internal parts still retaining 
a large portion of their original heat. If, then, we assume 
that the increments of temperature in descending are uni- 
form and equal to 1° Fahrenheit for every 45 feet of descent,* 
and that the limit of the solar influence is 100 feet below 
the surface, the temperature of boiling water will be reached 
in this part of the world (taking 52° as the surface tempera- 
ture) at (212° -52°) X 45 feet + 100 feet = 7300 feet below the 
surface, and a red heat (or say 752°) at a depth of 31,600 feet, 
or a very little less than six miles. The convex superficies 
of the earth = 196,813,000 square miles, and taking a mile 
and a half as the thickness of that part of the crust of which 
the temperature is under 212°, we have 295,219,500 cubic 
miles of a lower temperature than boiling water, the heat 
of the whole remaining portion of the earth's mass being 
* I am aware that some observations give a result of only 1° in 60 feet of 
descent as the rate of increment of temperature ; but whatever may be the 
rate, it can only aifect the numerical results, not the principles involved in 
this paper. 
