22 RELICS FROM THE WRECK 



sively slow operations, requiring the lapse of centuries to 

 accomplish the formation of a thin stratum. We are cer- 

 tain, therefore, that the building up of the gneissic and 

 mica-schist systems, by the abrasion of the granite, and 

 the gradual deposition of the detached matter at the bottom 

 of the ocean, must have required a period, with the vastness 

 of which the mind can hardly grj^ple, though perfectly in- 

 significant in His view, to whom " one day is as a thousand 

 years, and a thousand years are as one day." Of these two 

 groups, Dr. Macculloch remarks, " The thickness of these 

 strata we know to be enormous, their depths are discovered 

 by geological observations and inferences: that they ex- 

 tend to many miles was also proved. We have every 

 reason to know, from what is now taking place on our own 

 earth, that the accumulation of materials at the bottom of 

 the ocean, is a work infinitely slow. We are sure that such 

 an accumulation as should produce the primary strata as 

 we now see them, must have occupied a space, from the con- 

 templation of which the mind shrinks.* 



The silurian rocks underlay the old red sandstone of 

 England, and these are also estimated at 3,000 yards in 

 thickness. The slate rocks of Scotland are several miles 

 in thickness, and all exhibit the marks of slow deposition 

 and subsequent consolidation. " We have traced," says the 

 late Dr. James Douglas, of Glasgow, " a continuous ' out 

 crop 7 of these rocks along the coast of Argyle for seven 

 miles, and this is not one-third part of its extent. The 

 whole slate or schistose formations of the west Highlands 

 of Scotland generally l crop out' in a north-west direction, 

 and lie in an angle of from 45 to 70 or degrees. They 

 extend from about five miles below Dunoon, along the whole 



* There are seven distinct geological epochs each characterized by 

 sedimentary deposits of enormous thickness, and each the work of thou- 

 sands, if not millions of years. 



