382 Mr. J. Croll on Geological Time, and the probable 



country since the creation of man, according to Mosaic chrono- 

 logy, is certainly not a very great quantity. No person but one 

 who had some preconceived opinions to maintain would ever 

 think of concluding that one foot of soil daring 6000 years was 

 an extravagant quantity to be washed off the face of the country 

 by rain and floods during that long period. Those who re- 

 side in the country and are eye-witnesses of the actual effects 

 of heavy rains upon the soil, our soft country roads, ditches, 

 burns, and rivers, will have considerable difficulty in actually 

 believing that only one foot has been washed away during the 

 past 6000 years. 



Some may probably admit that a foot of soil may be washed 

 off during a period so long as 6000 years, and may tell us that 

 what they deny is not that a foot of loose and soft soil, but a 

 foot of solid rock can be washed away during that period. But 

 a moment's reflexion must convince them that, unless the rocks 

 of the country were disintegrating and decomposing as rapidly 

 into soil as the rain is carrying the soil away, the surface of the 

 country would ultimately become bare rock. It is true that the 

 surface of our country in many places is protected by a thick 

 covering of boulder-clay ; but when this has once been removed, 

 the rocks will then disintegrate far more rapidly than they are 

 doing at present. 



But slow as is the rate at which the country is being denuded, 

 yet when we take into consideration a period so enormous as 6 

 millions of years, we find that the results of denudation are really 

 startling. One thousand feet of solid rock during that period 

 would be removed from off the face of the country. But if the 

 mean level of the country would be lowered 1000 feet in 6 mil- 

 lions of years, how much would our valleys and glens be deepened 

 during that period ? This is a problem well worthy of the con- 

 sideration of those who treat with ridicule the idea that the ge- 

 neral features of our country have been carved out by subaerial 

 agency. 



In consequence of the retardation of the earth's rotation, oc- 

 casioned by the friction of the tidal- wave, the sea-level must be 

 slowly sinking at the equator and rising at the poles. But it 

 is probable that the land at the equator is being lowered by 

 denudation as rapidly as the sea-level is sinking. Nearly one 

 mile must have been worn off the equator during the past 12 

 millions of years, if the rate of denudation all along the equator 

 be equal to that of the basin of the Ganges. 



But if the rate of denudation be at present so great, what 

 must it have been during the glacial epoch ? It must have been 

 something enormous. At present, denudation is greatly retarded 

 by the limited power of our river- systems to remove the loose 



