Tra-s^es. — On ike former Warmth in liujh Northern Latitudes. 465 



therefore says that " he will assume that water belongs to the atmosphere, 

 and, iu the present order of things, should be found as a constituent of the 

 atmosphere of all the orbs of space ; the state of its existence, whether 

 solid, fluid, or gaseous, whether combined as water, or separated into 

 its constituents of free hydrogen and free oxygen, being dependent on the 

 physical conditions to which it is subjected." 



Now, it is scarcely necessary for me to remtu'lc that all life, as it is 

 known to us, is dependent upon the existence of water. This is a fact which 

 we learn from any elementary work on physiology, and we are, therefore, 

 justified in assuming that until water existed on our globe, at a temperature 

 not inconsistent with life, no life could be developed upon it. You have 

 before you on the table a series of sx^ecimens taken from the hot waters of 

 springs in the Eotomahana district, showing, in all probability, the very 

 highest temperatures compatible with the existence of living organisms, and 

 we may look back to a period counted, probably, by hundreds of millions 

 of years, when such low forms of life were the only ones which were to be 

 found on the surface of our planet. And this brings me to the immediate 

 subject of this paper, namely, had the heat radiated from the interior of our 

 globe, any effect upon climate during the earlier periods of life brought 

 under our notice by the geological records ? I venture, for reasons which I 

 will proceed to explain, to agree with the older ideas on the subject, in spite 

 of the positive opinions ex^Dressed by Sir Charles Lyell. 



It is clear that long before the surface conditions of our globe were such 

 as to permit of the condensation of aqueous vapour upon it, it revolved 

 round the sun in the orbit which it now occupies, and that even then the 

 heat of its ecjuatorial regions received a large increase from the latter body. 

 It will have been observed that the depth to which the surface is now 

 permanently heated by the rays of the sun diminishes with great rapidity as 

 we approach the equatorial regions, but there is no reason for . supposing 

 that during the gradual cooling of the globe, the radiation of heat would, 

 even supposing the absence of any check due to the sun's rays, have been 

 greater from the equatorial regions than from the polar ones. The contrary 

 must, in effect, have been the case, and the polar regions of our globe were 

 doubtless the earliest to present surface conditions fitted to retain water 

 upon them. If this were so, then certainly life must, in its earliest stages, 

 have had its origin in arctic latitudes, gradually extending towards the 

 tropics as the surface of the latter regions became sufficiently cool to permit 

 water to accumulate there also. It will, of course, be understood that the 

 accumulation of water on our globe was very slow, and I cannot but think 

 that the arguments brought forward by Mr. Mattieu AVilliams, in the work 

 alluded to, as to the materials which constitute the fuel of the sun, apply 



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