THE AGE OF THE EARTH.

Taranaki Herald, Volume LIV, Issue 13241, 13 August 1906, Page 3

THE AGE OF THE EARTH.

The age of tbc earth is a subject of ve_y co_a>ideVab2H *ntett3y* 'to us, but unfortunately opinions concerning it are somewhat ■ ccntradictory. In particular tih_ physicists and the geologiste 'fail su far to •agree. It -is 1 obvious that tfe calculations of both nmst bo very inox-act for 'miany un-l--no'wn conditions must be left out of the problem as stated by either. The estimate of the earth's a-go 'that has f or m-any years •held thw field ds that by Lord Kelvin, who, argiuing from, the rate of cooling, lisld that the earth must have been incandescent a 'lni-dr-d m illi on years ago . By a similar - method Kelvin investigated' tho 'age of the sun. The discovery of vadiulm and its heat-anitting property, uddod to the possibility -that similar radio-ac-tivity may have played «, large part, throws considerable dbubt on tho value of the temperature gradient as a safe guide, and; this classical estimate foU perhaps to) fee reckoned with imvny at'ht-r -acthievemen'ts of m_.thema | trcia_is which soan-ehow fail to square with nature.. We may in the light of i;htsso naw factors be nuuch okler t;han Lord Kelvin osthnatcd. Pi'o-v fa-rsor G. 11. Darwin calculates that tho moon separated . from us 57,000,000 years ago. '*Vc must, of course, at that ti-me ha*» 'been irtill plastic ; but here again the roason-'ng is .atetruscly unvthoaualical. and some very important factor DToy have btvn overlooked. Tait and Newco>r»i?b, on mudh the same lines, reckotu iimxt water first ■appeared "vj such sonic 30,000,000 years agO; ami vi thi« wm --o, it woul-d 'io a backwa'ixi limit for the foeginm -n^ o life. T'lvis ti-me, however, is toa short for the geologists. Wo know that our •jrcn-t livers will Yaiso th.c level of a BuJimratiary deposit by about lit in 158 years. _vow we have a total depth ol sedimentary rocks^ which ■h<a« been t-ctimatocl at 1?7,200ft. If things have gone on much as they do now—and the cataclysmic theory of history is at a discount — these rocks took 28,000,000 years to make. Again, even if we have no absolute sc_,la of measurement, we can estimate the relative length of each of the principal geologic ages. One writer, Professor Davis. n>presents the post-glacial period by 2in. The Tertiary must then occupy 10ft, the TTHnssic— the age of^big repiflea-^Oft, the coal beds 100 ft, and the Middle Cainbriaw— where the trilobite^ appear —100. Tins, of course, is n mere plan to suggest the relative extent of these epochs. If, however, the scheme is trustworthy,' and we could fix the date of the Ice age, thvn to could turn th:« feet and inches into years. Oroll's Hi.eory of the Ice age, making it dbpen-d on the eccentricity of the orbit, has for zowa time been under a" cloud, and the tendency is to •bring the ice ag>i> closer up -up* to within 3000 or 10,000 years. If that i» so, the Trinsslo age came, on Professor DavaVs scheme, 2,400,000 years ago ; the carboniferous 5,000.000 ; and w<i may consider the beginnings of life to 'hav;c happened ' aboiit 50,000,000 years ago— tho life that is of the wry lowewt- orgunisroi-but several coi^i'derations will draw the i«?tKn_vlo 'oi ]>liy.<ifi«t ft-nd •prolag'wt. closer. Tlie fiwst is already wilh-ng to lcoel-h«n Jiis : -he srcuh:l way '•«« °;v; v can 'do wi+h a shorter time. The biahruisl ' also v.-ill have something to i?i\y\ but. hw ennn'ot yet wtiinwte, "the rate of variation v,v!l onemgh lo make a i-caao-sablp quantitative gurss at how long tl»o pjocess of evolution must have bom/at work.