A GLIMPSE THROUGH THE CORRIDORS OF TIME. 491 



The height to which the tides rise and fall is so profoundly modi- 

 fied by the coasts and by the depth of the sea, that at present we find 

 at different localities tides of only a few inches and tides of sixty or 

 seventy feet. In ancient times there were no doubt also great varieties 

 in the tidal heights, owing to local circumstances. To continue our 

 calculations we must take some present tide. Let us discard the ex- 

 tremes just indicated and take a moderate tide of three-feet rise and 

 three-feet fall as a type of our present tides. On this supposition, 

 what is to be a typical example of a tide raised by the 40,000-mile 

 moon ? If the present tides be three feet, and if the early tides be 

 216 times their present amount, then it is plain that the ancient titles 

 must have been 648 feet. 



There can be no doubt that in ancient times tides of this amount, and 

 even tides very much larger, must have occurred. I ask the geologists 

 to take account of these facts, and to consider the effect a tidal rise 

 and fall of 648 feet twice every day. Dwell for one moment on the 

 sublime spectacle of a tide of 648 feet high, and see what an agent it 

 would be for the performance of geological work ! We are now stand- 

 ing, I suppose, some 500 feet above the level of the sea. The sea is 

 a good many miles from Birmingham, yet if the rise and fall at the 

 coasts were 648 feet, Birmingham might be as great a sea-port as Liv- 

 erpool. Three quarters tide would bring the sea into the streets of 

 Birmingham. At high tide there would be about 150 feet of blue 

 water over our heads. Every house would be covered, and the tops 

 of a few chimneys would alone indicate the site of the town. 



In a few hours more the whole of this vast flood would have re- 

 treated. Not only would it leave England high and dry, but probably 

 the Straits of Dover would be drained, and perhaps even Ireland would 

 in a literal sense become a member of the United Kingdom. A few 

 hours pass, and the whole of England is again inundated, but only 

 again to be abandoned. 



These mighty tides are the gift which astronomers have now made 

 to the working machinery of the geologist. They constitute an engine 

 of terrific power to aid in the great work of geology. What would 

 the puny efforts of water in other ways accomplish when compared 

 with these majestic tides and the great currents they produce ? 



In the great primeval tides will probably be found the explanation 

 of what has long been a reproach to geology. The early Palaeozoic 

 rocks form a stupendous mass of ocean-made beds which, according to 

 Professor Williamson, are twenty miles thick up to the top of the Silu- 

 rian beds. It has long been a difficulty to conceive how such a gigantic 

 quantity of material could have been ground up and deposited at the 

 bottom of the sea. The geologists said, "The rivers and other agents 

 of the present day will do it if you give them time enough." But, 

 unfortunately, the mathematicians and the natural philosophers would 

 not give them time enough, and they ordered the geologists to " hurry 



