Sir A. Geilde—Age of the Earth. 463 



have long since disappeared, can still be followed for mile after mile 

 across the mountains and glens of the North- West Highlands. So 

 tranquil were these waters that their gentle currents and oscillations 

 sufliced to ripple the sandy floor, to arrange the sediment in laminte 

 of current-bedding, and to separate the grains of sand according to 

 their relative densities. We may even now trace the results of these 

 opex'ations in thin darker laj'ers and streaks of magnetic iron, zircon, 

 and other heavy minerals, which have been sorted out from the 

 lighter quartz-grains, as layers of iron-sand may be seen sifted 

 together by the tide along the upper margins of many of our sandy 

 beaches at the present day. 



In the same ancient formation there occur also various intercala- 

 tions of fine muddy sediment, so regular in their thin alternations, 

 and so like those of younger formations, that we cannot but hope 

 and expect that they may eventually yield remains of organisms 

 ■which, if found, would be the earliest traces of life in Europe. 



It is thus abundantly manifest that even in the most ancient of 

 the sedimentary registei's of the earth's history, not only is there 

 no evidence of colossal floods, tides, and denudation, but there is 

 incontrovertible proof of continuous orderly deposition, such as may 

 be witnessed to-day in any quarter of the globe. The same tale, 

 with endless additional details, is told all through the stratified 

 formations down to those which are in the course of accumulation at 

 the present day. 



Not less important than the stratigraphical is the palseontological 

 evidence in favour of the general quietude of the geological processes 

 in the past. The conclusions drawn from the nature and arrange- 

 ment of the sediments are corroboi-ated and much extended by the 

 structure and manner of entombment of the enclosed organic remains. 

 From the time of the \evy earliest fossiliferous formations there is 

 nothing to show that either plants or animals have had to contend 

 with physical conditions of environment different, on the whole, 

 from those in which their successors now live. The oldest trees, 

 so far as regards their outer form and internal structure, betoken an 

 atmosphere neither more tempestuous nor obviously more impure 

 than that of to-day. The earliest corals, sponges, crustaceans, 

 moilusks, and arachnids were not more stoutly constructed than 

 those of later times, and are found grouped together among the 

 rocks as they lived and died, with no apparent indication that any 

 violent commotion of the elements tried their strength when living 

 or swept away their remains when dead. 



But, undoubtedly, most impressive of all the palgeontological data 

 is the testimony borne by the grand succession of organic remains 

 among the stratified rocks as to the vast duration of time required 

 for their evolution. Professor Poulton has treated this brancli of 

 the subject with great fulness and ability. We do not know tlie 

 present average rates of organic variation, but all the available 

 evidence goes to indicate their extreme slowness. They may con- 

 ceivably have been more rapid in the past, or they may have been 



