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 affect the numerical results, not the principles involved in 

 this paper. 



