Nov. i6, 1888.] 



SCIENTIFIC NEWS. 



517 



distinguished, and I know in some instances what the 

 answer will be. The third objection is of a general 

 nature. To prevent the possibility of misstatement I will 

 give it as a quotation : " To a geologist (especially one 

 belonging to the school of Lyell) it is equally difficult to 

 conceive that there should be a broad distinction between 

 the metamorphir rocks of Archaean and post-Archaean 

 age respectively, as that the pre-Tertiary volcanic 

 rocks should be altogether different in character 

 from those of Tertiary and recent times." 

 Of course in this statement much depends on the 

 sense attached to the epithet " broad." As an abstract 

 proposition I should admit, as a matter of course, that 

 from similar causes similar consequences would always 

 follow. But in the latter part of the quotation lurks a 

 petitio priucipii. During the periods mentioned volcanic 

 rocks appear, as we should expect, to have been ejected 

 from beneath the earth's crust similar in composition and 

 condition, and to have solidified with identical environ- 

 ment. Hence the results, allowing for secondary changes, 

 should still be similar. But to assume that the environ- 

 ment of a rock in Early Archaean times was identical 

 with that of similar material at a much later period is to 

 beg the whole question. My creed also is the uniformi- 

 tarian, but this does not bind me to follow a formula into 

 a position which is untenable. Other studies with which 

 I have some familiarity have warned me that a blind 

 orthodoxy is one of the best guides to heresy. " The 

 weakness and the logical defect of uniformitarianism " — ■ 

 these are Professor Huxley's words — " is a refusal, or at 

 least a reluctance, to look beyond the ' present order of 

 things,' and the being content for all time to regard the 

 oldest fossiliferous rocks as the ultima Thule of our sci- 

 ence." Now, speaking for myself, I see no evidence 

 since the time of these rocks, as at present known, of any 

 very material difference in the condition of things on the 

 earth's surface. The relations of sea and land, the cli- 

 mate of regions, have been altered, but because I decline 

 to revel in extemporised catastrophes, and because I 

 believe that in nature order has prevailed and law has 

 ruled, am I therefore to stop my inquiries where life is 

 no longer found, and we seem approaching the firstfruits 

 of the creative power ? Because palaeontology is per- 

 force silent ; because the geologist can only say '' I know 

 no more," must I close my ear to those who would turn 

 the light of other sciences upon the dark places of our 

 own, and meet their reasoning with the exclamation, 

 " This is not written in the book of uniformity " ? To 

 do this would be to imitate the silversmiths of old, and 

 silence the teacher by the cry, " Great is Diana of the 

 Ephesians." 



What, then, does the physicist tell us was the initial 

 condition of this globe ? I will not go into the vexed 

 question of geological time, though as a geologist I must 

 say that we have reason to complain of Sir W. Thomson. 

 Years ago he reduced our credit at the bank of time to a 

 hundred millions of years. We grumbled, but submitted- 

 and endeavoured to diminish our drafts. Now he has 

 suddenly put up the shutters and declared a dividend of 

 less than four shillings in the pound. 1 trust some 

 aggrieved shareholder will prosecute the manager. How- 

 ever, as a cause celebre is too long a business for the end 

 of an evening, I will merely say that while personally I 

 see little hope of arriving at a chronological scale for the 

 age of this earth, I do not believe in its eternity. What, 

 then, does the physicist tell us must have been in the 

 beginning ? I pass by those earliest ages, when, as 



" Ilion, like a mist, rose into towers," so from the glow- 

 ing cloud the great globe was formed. I pass on to a 

 condition more readily apprehended by our faculties — 

 the time — the consislentior status of Leibnitz — when the 

 molten globe had crusted over, and its present history 

 began. Rigid uniformitarian though you may be, you 

 cannot deny that when the very surface of the ground 

 was at a temperature of at least 1,000 degs. F., there was 

 no rain, save of glowing ashes — no river, save of molten 

 fire. Now is ending a long history with which the 

 uniformitarian must not reckon — of a time when 

 many compounds now existing were not dis- 

 solved but dissociated, for combination under that 

 environment was impossible. Yet there was still law 

 and still order — nay, the present law and order may be 

 said even then to have had a potential existence — never- 

 theless to the uniformitarian gnome, had such there been, 

 every new combination of elements would have been a 

 new shock to his faith, a new miracle in the earth's 

 history. But at the times mentioned above, though 

 oxygen and hydrogen could combine, water could not yet 

 rest upon the ruddy crust of the globe. What does that 

 mean ? This, that assuming the water of the ocean 

 equivalent to a spherical shell of the earth's radius and 

 two miles thick, the very lava stream would consolidate 

 under a pressure of about 310 atmospheres, equivalent 

 to nearly 4,000 feet of average rock.* But on the practical 

 bearing of this consideration I will not dwell. Let us 

 pass on to a time, which, according to Sir W. Thomson, 

 would rather quickly arrive, when the surface of the 

 crust had cooled by radiation to its present temperature. 

 Let us, merely for illustration, take a surface temperature 

 of 50 F. (nearly that of London), and assume that the 

 present rise of crust temperature is i° F. for every 50 

 feet of descent, which is rather too rapid. If so, 212° F. 

 is reached at 8,100 feet, and 250 F. at 10,000 feet. 

 Though the latter temperature is far from high, yet we 

 should expect that under such a pressure, chemical 

 changes would occur with much more facilty than at the 

 surface. But many Palaeozoic or even later rock masses 

 can now be examined whi;h at a former period of their 

 history have been buried beneath at least 10,000 feet of 

 sediment ; yet the alteration of their constituents has been 

 small ; only the more unstable minerals have been some- 

 what modified, the more refactory are unaffected. But 

 for a limited period after the consislentior status, the 

 increase of crust temperature in descending would be far 

 more rapid ; when one twenty-fifth of the whole period 

 from that epoch to the present had elapsed, and this is 

 no inconsiderable fraction, the rate of increase would be 

 1 ? for every ten feet of descent. Suppose, for the sake 

 of comparison, the surface temperature as before, the 

 boiling-point of water would be reached at 1,620 feet, 

 and at 10,000 feet, instead of a temperature of 250 F., 

 we should have one of 1,050° F. But at the latter 

 temperature many rock masses would not be perfectly 

 solid, f According to Sorby the steam cavities in the 

 Ponza trachyte must have formed, and thus the rock have 

 been still plastic at so low a temperature as 680' F. At 

 this period then, the end of the fourth year of the geolo- 

 gical century, whatever be its units, structural changes in 

 igneous and chemical changes in sedimentary rocks must 

 have occurred more readily than in any much later period 



* If we take the S.G. of water as unity, and that of mean rock as 

 2"7, the pressure would be = 3,9iri feet of rock. 



f The lowest temperature, which, so far as I know, has been 

 observed in lava (basic) while still plastic, is 1,2280 F. 



