Ixvi REPORT — 1856. 



was present in the grain, it being evident that any excess must have been 

 derived from the rock from which it drew its nourishment. 



Should it appear by an extensive induction of particulars, that none of 

 the rociis lying at the base of the Silurian formation, which have come before 

 us, contain more phosphoric acid than the minute quantity I detected in the 

 slates of Bangor and Llanberris, which were tested in the above manner, it 

 might perhaps be warrantable hereafter to infer, that we had really touched 

 upon those formations that had been deposited at a time when organic beings 

 were only just beginning to start into existence, and to which, therefore, the 

 term Azoic, assigned to these rocks by some of the most eminent of our geo- 

 logists, might not be inappropriate. 



The proofs of the former extension of glaciers in the northern hemisphere, 

 far beyond their actual limits, tend also to complicate the question which has 

 at all times so much engaged the attention of cosmogonists with respect to 

 the ancient temperature of the earth's surface ; compelling us to admit, that 

 at least during the later of its epochs, oscillations of heat and cold must have 

 occurred, to interfere with the progress of refrigeration which wa^ taking 

 place in the crust. 



On the other hand, facts of an opposite tendency, such as the discovery 

 announced at our last Meeting by Captain Belcher, of the skeleton of an 

 Ichthyosaurus in lat. 77°, have been multiplying upon us within the same 

 period ; inasmuch as they appear to imply, that a much higher temperature 

 in former times pervaded the Arctic regions than can be referred to local 

 causes, and therefore force upon us the admission, that the internal heat of 

 the nucleus of our globe must at one time have influenced in a more marked 

 manner than at present the temperature of its crust. 



On the causes of this increased temperature, whether local or cosmical, 

 much elaborate research has been brought to bear, by Sir Charles Lyell in 

 his celebrated ' Principles of Geology,' and by Mr. Hopkins in his Address to 

 the Geological Society. 



The most extensive collection of facts, however, having reference to this 

 subject, is contained in the Reports on Earthquake Phsenomena, published 

 by Mr. Mallet in our Transactions, supplying, as they do, data of the highest 

 importance to the full elucidation of the subject. For although the evidence 

 I have myself brought togetiier in ray work on Volcanos might be sufficient 

 to establish in a general way the connexion of earthquakes with that deep- 

 seated cause which gives rise to the eruptions of a volcano, yet our interest 

 is thereby only the more awakened in the phaenomena they present, — ^just as 

 Dr. Whewell's inquiries into the local variations of the Tides were valued all 

 the more in consequence of the persuasion already felt, that lunar attraction 

 was their principal cause. 



But if earthquakes bring under our notice chiefly the dynamical effects of 

 this hidden cause of movement and of change, those of volcanos serve to 

 reveal to us more especially their chemical ones ; and it is only by com- 

 bining the information obtained from these two sources, together with those 

 from hot springs, especially as regards the gaseous products of each, that we 

 can ever hope to penetrate the veil which shrouds the operations of this 

 mysterious agent; so as to pronounce, with any confidence, whether the 

 effects we witness are due, simply to that incandescent state in which our 

 planet was first launched into space, or to the exertion of those elective at- 

 tractions which operate between its component elements, — attractions which 

 might be supposed to have given rise, in the first instance, to a more ener- 

 getic action and consequently to a greater evolution of heat, than is taking 



