Show THE N ha sun when it filled much larger space than now was greater than at present it Is a rather startling act that the sun s heat were increased b much more than one halt it would boil away all the water on the globe As water Is necessary to life on the globe prof newcomb our great authority at washington thinks that the balance ot causes which would result in the sun radiating heat just fast enough to preserve the earth in its present state has probably not existed more than years and that this Is therefore near the extreme limit of time that we can suppose water to have existed on the earth in the fluid state but though the mathematicians insist that some such limit as or years must be placed upon the existence of even the lowest forms of life on the earth geologists still contend for a longer lease of time reasoning aiom the known rate at which forms of life change darwin and lyell assumed that it must have been on the earth for many hundred million years darwin indeed in his earl er e lotions of the origin of species speaks of years as a mere trifle of geologic time but the geologists of the present day are more modest in their demands and would apparently ly be satisfied with or twice that num her of years alfred russell wallace however from geological evidence calculates that years is all that need be demanded fot the facts of geology wallace s estimate is an inte esting one taking the thickness of the sedimentary bedi at feet which is an extreme estimate and reckoning the coast line of the globe at miles and that the sediment brought into the sea is deposited on an average over a belt 30 miles wide he finds that at the present rate the total thickness of rocks would be formed within the above mentioned length ot time for at the present rate of slon of the continents the whole land surface of the earth ls lowered one foot in 3 years and the sediment deposited along the of the continents one foot from 57 square miles the land surface of the earth is equal to 19 feet deposited in 3 years over the belt stretching 30 miles out aiom miles ot shore line divided by 19 multiplied by equals 28 such Is the reduction to the age of the world made by the more recent investigations both of astronomers and geologists assuming the truth of the nebular 1 po thesis prof george H darwin obtained results remark ably similar from calculations concerning the relations of the moon to the earth the moon produces tides up on the earth and conversely the earth must produce tides upon the moon As was long ago shown these tides re tard the dally motion of the revolution of these bodies the tides are equivalent to a wave on the earth about three feet high striking twice a day on the eastern shore of the continents this has the same effect as a brake on a wheel and imperceptibly but surely retards its motion As the moon is much smaller than the earth and hence has less momentum its motion has been at fectea much more by its tides than has that of the earth whereas the moon once revolved on its axis very rapidly it now requires a whole month to revolve and so keeps the same face toward the earth all the time it Is estimated that to produce the present amount of heat the diameter of the sun must contract feet per year or a mile in 25 years tour miles a century though this Is too small an amount to have been noted by any present means of measurement since accurate observe alons began to be made it is by no means an insignia cant amount by darwin u calculation it was shown that formerly the earth revolved on its axis once every eight hours but was reduced to Us present rate by the same process that has reduced the moon at the time when the moon and earth were revolving so rapidly they were much nearer to each other than now indeed so near that the tides they produced on each other were many times as great as those now pro deuced so great indeed waa the tidal wave which then rolled over the world that it is hardly possible to suppose that any form of life could have endured the con dillons going further mr darwin proved that the moon was originally thrown off from the mass of earth by the in creased centrifugal motion of the contracting sphere of the earth as water is thrown off from a grindstone furthermore by his calculations of the retarding influx ence of the tides he proves that this could not have oc burred less than 50 nor more than years ago all geologic time therefore must be brought much within these limits for after the birth of the moon an immensely long period must have elapsed before the conditions were such upon the earth that life could have endured them so that his calculations agree in a remarkable manner with those of mr wallace and of prof newcomb but 1 years Is a long time and slowly work ing causes produce immense results within that period As darwin remarks few ot us know what a million really means take a narrow strip of paper 83 feet tour inches in length and stretch it along he wall ol 01 a large hall then mark off at one end the tenth of an inch this tenth of an inch will represent years and the strip a million years bearing this in mind we shall appreciate the following calculations concern ing the great length of the geological periods even on mr wallace s estimate of the total length ot geological time and they will seem sufficiently long for all feces sary purposes dana estimates the ratio tor the paleozoic mesozoic and cenozoic periods to be 12 3 1 that Is ceno times the time since the beginning of the ter biary period is one sixteenth of the whole or about 2 years mesozoic time the age of the alence of reptiles would be about three sixteenths ot the time or G years while time would be about three fourths of the time that is about 20 years it however we should be compelled to accept the calculations of prof newcomb these would have to be reduced more than one hall but the accumulating facts concerning the rapidity of the action of present geological forces seem to be pointing toward these lower estimates and to make it entirely credible that the earth has not been suitable for the existence of man for very many thousand years the loose estimate in which hundreds of thousands of years are assigned to the existence of the human race take little account of the real facts which are coming to light |