5*4 REPORT — 1876. 



Sir W. Thomson did good service by calling in question, on physical grounds, 

 the indefinite extension backwards of geological time. The iirstfruits of his crusade 

 were the definitions of Uniformitariauism and Evolution which Prof. Huxley gave. 

 Henceforth no one will maintain the onesided notions regarding these two opposing 

 views of the earth's history which were adopted in ignorant misconception or dic- 

 tated by conceit and bigotry. But the service done was even greater; for while it 

 became clear that a knowledge of physics was indispensable to him who would 

 promulgate sound notions, it was further apparent that both biological and geolo- 

 gical evolution had a limit in time, that in fact, on the assumption of the primitive 

 incandescence of our globe, the date might be at least approximately fixed when 

 the mechanical processes now at work commenced and when the surface of the 

 earth became habitable. Nothing more has yet been done than to point out the 

 way ; for, though Prof. Guthi-ie Tait indicates a limit of from 15 to 10 millions of 

 years, that statement can only be regarded as in efiect, though not perhaps in in- 

 tention, a protest against the liberality and vagueness of Sir W. Thomson's allow- 

 ance, which gave geologists a range of from one to two hundi'ed millions of 

 years. 



The reconciliation of physicists and geologists is not likely to come through 

 Mr. Lockyer's researches, even if the earth's history be shown to have 

 been identical, unless the renewal of the earth's heat be shown to be compatible 

 with continued life on the surface. If the reconciliation is looked for through the 

 prolonged duration of the sun's life, that being the gauge of the earth's duration, 

 the expectation is still based on the supposed need of very great time for geological 

 processes, or rather on the supposed need of very great time for biological evolution, 

 to which geological evolution has been squared. There is another direction in 

 which these results may help us to meet the limitation assigned by the physicists : 

 the intervals of variation of temperature may be shorter than those which separate 

 the maxima of eccentricity of the earth's orbit; and thus the repeated cold periods 

 of which we have suggestions in the stratified rocks, may have recuiTcd within a 

 sliorter total period than is at present claimed. 



It is scarcely within the compass of this address to enter into the questiDus in- 

 volved ; but it is permissible to indicate the reason for delaying meanwhile accep- 

 tance of any precise limit of time. There is as yet too much diversity of opinion 

 as to the elements of the problem. Physicists are by no means at one as to the 

 conditions which permit or prohibit shifting of the earth's axis. Oalcidations are 

 based on the assumption of the regularity of the earth's form, under a certain con- 

 .<stant relation of the masses, albeit of diverse specific gravity, which compose it. 

 It is moreover assumed that the ratio of land and water have been uniform, though 

 the formation of the grand features of the land by contraction of the cooling mass 

 has not yet been considered as affecting this assumption by altering the disposition 

 of the water. On the one hand it has been shown that the existence of uniform 

 temperatures over the earth's surface is a gratuitous hypothesis ; on the other 

 hand it is clear that the existing distribution of light and heat is incompatible with 

 the flourishing of an abundant Carboniferous and Miocene flora within a short 

 distance of the north pole. One expects tliat astronomers will look to the shifting 

 of the axis of rotation as the possible explanation of the difficulty, taking into 

 account likewise the shifting of the centre of gravity necessarily following those 

 displacements of matter which, on the contraction theory, liave determined the 

 positions of the main continents and oceans. 



Mr, Evans, in his address to the Geological Societ}', refeiTcd to the deviation of 

 the magnetic axis as perhaps due to such shifting of the materials composing the 

 inner mass of our globe. May not the conjectures of M. Elie de Beaumont be 

 after all in the right direction ? May not the change of trend which led him to 

 classify the mountain-chains by reference to the age at which they had been ele- 

 vated, be associated with movements which did not in all cases result in shiftings 

 of the earth's axis so pronounced as those which permitted the Carboniferous and 

 Miocene floras to invade successfully the arctic regions, or the phenomena of the 

 glacial epoch, or epochs, to manifest themselves in the low latitudes where their 

 traces have been recognized ? 



AVaiving, for the present, inquiry into the influence which the admission of a 



