ADDRESS. Ixix 



earth's orbit to be as 19 to^2G, according as the winter would take place wbeu 

 the earth was in aphelion or in perihelion. His reason may be briefly stated 

 thus : assuming the mean annual heat to be the same, whatever the excen- 

 tricity of orbit, yet if the extremes of heat and cold in winter and summer 

 be greater, a colder climate vnH prevail, for there will be more snow and ice 

 accumulated in the cold winter than the hot summer can melt — a result, aided 

 by the shelter from the sun's rays, produced by the vapour suspended in 

 consequence of the aqueous evaporation ; hence we should get glacial periods, 

 when the orbit of the earth is at its greatest excentricity, at those parts of the 

 earth's surface where it is winter when the earth is in aphelion ; carboni- 

 ferous or hot periods where it is Avinter in perihelion ; and normal or tem- 

 perate periods when the excentricity of orbit is at a minimum ; all these would 

 gradually slide into each other, and would produce at long distant periods 

 alternations of cold and heat, several of which we actually observe in geo- 

 logical records. 



If this theory be borne out, we should approximate to a test of the time 

 which has elapsed between different geological epochs. Mr. CroU's compu- 

 tation of this would make it certainly not less than 100,000 years since the 

 last glacial epoch, a time not very long in geological chronology — probably it 

 is much more. 



When we compare with the old theories of the earth, by which the 

 apparent changes on its surface were accoimtcd for by convulsions and 

 cataclysms, the modern view inaugurated by LyeU, your former President, and 

 now, if not wholly, at all events to a great extent adopted, it seems strange 

 that the referring past changes to similar causes to those which are Jiow in 

 operation should have remained iminvestigated until the present century ; 

 but Math this, as mth other branches of knowledge, the most simple is fre- 

 quently the latest view which occurs to the mind. It is much more easy to 

 invent a Deux ex macliind than to trace out the influence of slow continuous 

 change ; the love of the marvellous is so much more attractive than the 

 patient investigation of truth, that we find it to have prevailed almost uni- 

 versally in the early stages of science. 



In astronomy we had crystal spheres, cycles, and epicycles ; in chemistry 

 the philosopher's stone, the elixir vitse, the archseus or stomach demon, and 

 phlogiston ; in electricity the notion that amber possessed a soul, and that a 

 mysterious fluid could knock down a steeple. In geologj' a deluge or a volcano 

 was supplied. In palaeontology a new race was created whenever theory 

 required it : how such new races began, the theorist did not stop to inquire. 



A curious speculator might say to a palaeontologist of even recent date, in 

 the words of Lucretius, 



" Nam ncque de coelo ceciclisse auimalia possuiit 



Wee terrestria do salsis cxisse lacunis. 

 ***** 



E uihilo si crcscere posscnt, 

 (Turn) ficrcnt juveues siibito ex infantibus parvis, 

 E tcrraque exorta rcpente ai-busta salii-cnt ; 

 Quoi'ura nil fieri manifcstum est, omnia quando 

 Paulatiiu crescunt, ut par est, semine certo, 

 Crcscentesque genus servant" 



— which may be thus freely paraphrased : " You have abandoned the belief 

 in one primaeval creation at one point of time, you cannot assert that an ele- 

 phant existed when the first saurian s roamed over earth and water. Without, 

 then, in any way limiting Almighty power, if an elephant Avere created 

 without progenitors, the first elephant must, in some way or other, have 



