251 



XI. — On the Original and Actual Fluidity of the Earth and Planets. By the 

 Eev. Samuel Haughton, M. A., Fellow of Trinity College, and Professor 

 of Geology in the University of Dublin. 



Read May 12, 1851. 



J- HE communication which is here offered to the Academy contains a brief 

 examination of the three following questions : 



1st. Whether the nebular hypothesis of Laplace affords an explanation 

 of the equality of the mean movements of rotation and revolution of the moon 

 and other satellites. 



2nd. Whether the evidence of the original fluidity of the earth and 

 planets, afforded by their observed figures, is satisfactory with respect to all the 

 planets. 



3rd. Whether we possess, from the data afforded by astronomy, sufficient 

 knowledge of the structure of the interior of the earth to enable us to draw 

 conclusions respecting it, which are of geological value. 



The answer which I have given to each of these questions is in the nega- 

 tive, and the object I have had in view in offering this communication will be 

 accomplished, if it should in any way assist inquirers in estimating at their 

 just value speculations relating to the original condition of the earth. The im- 

 portance of such speculations has been, I believe, greatly overrated, and they 

 have been too readily applied to the explanation of some geological facts, for 

 which other and more probable causes can be assigned; such as the changes 

 of climate which have taken place on the surface of the earth, and the increase 

 of temperature as we descend below its surface. I have, therefore, examined 

 these questions with the view of proving that, if we confine ourselves to the 

 facts which we certainly know respecting the earth and planets, neither the ne- 

 bular hypothesis, nor the hypothesis of the internal fluidity of the earth, is 

 entitled to take a place in the list of positive facts. 



VOL. XXII. 2 L 



