NATURE NOTES.

New Zealand Herald, Volume LXIV, Issue 19660, 11 June 1927, Page 1 (Supplement)

NATURE NOTES.

BY J. DRUMMOUD, T.L.3., F.Z.S,

THE AGE OF THE EARTH.

An old controversy between geologists and physicists as to the age of the earth has been brought up by Mr. J. Alison, Pukgmiro. Quoting the physicists first, he refers particularly to Lord Kelvin's estimate of a minimum of 20,000,000 years. Tho principal geologist he quotes against this is Sir Archibald Giekie, with his minimum of 73,000,000 years and maximum of 680,000,000 years. lie asks if, since those estimates were made, there have been other and more accurate methods of computing the earth's age. In plumbing the depths of time, men of science necessarily abandon all pretence of exactitude. They deal in millenniums with the easy grace of a boy counting, the hours at school. So vast are the computations that a few million years more or less are neither here nor there. Geologists measured the quantity of sediment deposited in a year, applied the figures to the estimated thickness of the sedimentary rocks, and based their estimates of the earth's age on the result. They assumed that, in this case, the present is a safe guide to the past. More particularly they based computations on the saltness of the sea. They estimated the quantity of dissolved salts derived from tho weathering of rocks and added by river-waters to the sea every year. They estimated the total quantity of salt in Jlie sea and the time required to deposit- it there, and used that for their estimates of the earth's age. These estimates ranged from 70,000,000 to 150,000,000 years. They regarded some indefinite age, between those estimates, as inevitable. Lord Kelvin, a physicist, suddenly staggered the geologists with his famous declaration that the earth was cooling, and that less than 20,000,000 years ago, it must have been too hot to support any life whatever. It should be explained that the term " age of the earth " in this controversy generally means the time during which the earth's surface has been suitable for living beings. The laugh was on the geologists. Lord Kelvin bankrupted them. Ho struck a blow at evolutionists, who demanded much more than 20,000,000 years. It was not a knock-out blow. They simply held back, said that their evidence was clear, that evolution was the thing, and that time for it to take place there must have been. • Lord Rayleigh, another physicist, saw that with the discovery of radio-active elements a more reliable geological clock was available. He determined the quantity of radium in the upper parts of the earth and assumed that there arc the same quantities of it to a depth of twenty miles. The earth loses heat by radiation, but, it is believed, there are sufficient radio-active elements in the earth's crust to account, by the heat of transformation, for the leakages. That disposes of Lord Kelvin's theory of the earth's cooling. A largo number of radio-active transformations of one element into another have boon discovered. Efforts to alter the rate of a radio-active transformation have failed. For that reason radio-active changes seem to provide a reliable means of* estimating time- in the history of the earth. An idea of the rate of transformation is given by the fact that 6 per cent, of a quantity of uranium changes into helum and lead in 370,000,000 years. One worker found that a substance contained 280,000,000 times, as much helium as the same substance could generate in a'year. He concluded that at least 280,000,000 years were required to generate it. Estimating the quality of radio-active suustauces and tneir rata of disintegration, Kayieign declared that rauio-active research niuicated* about i,Uuu,UOU,UOu yeais as the tune during wlncli the earth has been suitable lor ihe» habitation oi living beings, lne bankrupt geuiugisi, formerly almost ruined by a physicist, now, lit the words oi an English proiessor, is made a capitalist by pnysicists, with more lujids in the bank ihan he knows what to do with. The most generally accepted geological estimates must be multiplied ten or twenty times in order to agree with physicists' revised estimates. This is consistent with the geological evidence. The position is stated graphically by an American geologist. lie describes biology and geology, on this shadowy road, running ui tandem, biology prancing in front, geology trotting at the shatt. Lord Kelvin declared that the feed on hand would not allow the tandem to go as lar as proposed. ' J. lie tandem was reined in, and came to a standstill. A new team, a four-in-hand, was brought out, astronomy and physics, in front, leading off at a great pace; biology at the pole, steadying the team; geoiogy plodding along as tho original wiieel-horse. The old wheel-horse lias become stiff in ins paces. Lord Kelvin checked him too high. A reasonable check would have given him good form and some sense of restraint. Checked too high, he took to short mincing steps. As a result, he is in poor shape to swing into the great pace Of the new leaders. It is too much to expect him to recover his natural step at once, but it is believed that he will do so jin time. For the present he will need a touch of the whip occasionally to make him keep pace. " Let this be gentle and considerate, because of his age and his past service," this geologist implores, " but let it be persuasive." articio on uaoijues, extinct crustaceans, lound in a uouidcr in liic i'aturau xviver, near Couiugwood, iod iVir. Aliioon to asK lor tins aiticic on the agt. oi tiie earth. xl was stated that iuu cjollingwood lossus belong to tile Urduv'ictah i'eriou, estimated >at some -»du,uuU,oUO yeaib ago. in the Cambrian i'enod, Which immediately pteceued the Urdovician, there lived a tniobue, INeoleiius, whoso dcgiee oi specialisation m organs and structure is astonishing. " Ncoienus," an American palaeontologist states, " stands lor a tremeudous conception of the vastness ol time belnnd it. I'his inconspicuous being, standing back behind us m the dun uavs oi the Caniui'ian, snipped bare now oy tne arduous labours of its discoverer, reveals a creatine so highly specialised that it must have commanded uncountable ages for its production by any process ot organic development sucn as that to which we palaeontologists give our allegiance. behind Neoienus is the problem now there developed out of the unicellular expression of life, under favouring physical conditions, this intricate and closely functioning organism." Tins writer asked if the distance from that creature with its full equipment ol sense-nerves, its elaborate digestive tract, and its organs of circulation, of reproduction, and of waste, to tho most highly specialised living beings of these times, is greater than the distance from the nuclear cell, held to be the seat of life, up to that marvellously specialised trilobite, completely blotted out ages ago. Starts are slow, progress is deliberate, the momentum of development is acquired very gradually. With theso considerations in mind, tho writer answers his own question. He states: "On the basis of the structure of this ancient trilobite alone, it is safe, and probably necessary, to answer that Neoienus was further from the beginning of life—vory, very much further in tho highest, probability—than we are from Ncolonus.".