68 



Below these lie the Middle Silurian, or May Hill and Llandovery beds, 

 though some geologists believe that the Upper Llandovery, or IMay HUl Sandstone, 

 as seen at Norbuiy and May Hill, might more faii'ly be classed with the Upper 

 Silurian, and the Lower Llandovery with the Lower Silurian. 



Then comes the tremendously thick series of beds called Lower Silurian ; 

 the first subdivision of which, named Caradoc, from Caer Caradoc, near Stretton, 

 is estimated to be 12,000 feet thick, is well seen in the valley of the Onny, above 

 Streflord Bridge. It contains many very beautiful fossils, particularly the 

 Triuncleus concentrkus, with its perforated fringe to the head. We must now go 

 again out of our own district to find the next lower formation,— the LlandUo, 

 Upper and Lower, which is of very great thickness (chiefly from the quantity of 

 volcanic ashes and lava which is interbedded with it), and is well shewn in the 

 Stiperstone district, and also at BuUth and Llandrindod. 



Below these come the Upper and Lower Cambrian strata including the 

 Tremadoc slates and Lingula flags (both which, however. Sir E. Murchison classes 

 with his Lower SUmian), and lastly the Longmynd series, which alone is supposed 

 to be 6,000 feet thick. This last deposit, in Carnarvonshii-e, produces the cele- 

 brated Bangor slates— the best in the world— though at the Longmynd it is fit for 

 nothing but road metaL 



Last of all known sedimentary rocks we find in Canada, and on the north- 

 west coast of Scotland, a series of beds, estimated to be 30,000 feet thick, denomi- 

 nated Laurentian, from the river St. Lawrence ; but these beds have only yielded 

 as yet, one fossQ remain— the Eozoon Canadcnse, though in the Longmynd beds, 

 which were formerly considered to be destitute of any signs of life, and therefore 

 termed azoic, the researches of my friend, Mr. Hicks, at St. David's, have 

 recently brought to light the remains of several species of Trilobites, some of them 

 of large size. 



Now let us take notice that each of these formations contains a different 

 series of fossils, but few being found in two consecutive beds, — and not only so, 

 but each of these formations has been subdivided into several subordinate divi- 

 sions, each of which contains fossils peculiar to itself. Then, remembering the 

 thousands of years that have elapsed since man first appeared on earth without 

 any material change in animal life, as is proved to a great extent by the paintings 

 and sculptures of the early Egyptians and Assyrians depicting our existing 

 animals. Keflect what an inconceivable time must have passed away ere these 

 various destructions and renewals of forms of life could have been brought about. 

 Perhaps it may aid you in conceiving the duration of time thus occupied to refer 

 to the accounts given by Sir Chas. Lyell and Dr. Dawson, of the section of the 

 coal-bearing strata of the carboniferous formation seen in the lofty cliffs called the 

 South Joggins, on the Bay of Fundy in Nova Scotia. The cliffs are from 150 to 

 200 feet in height, and the beds dip at an angle of 24°, enabling you as j-ou walk 

 along the shore to examine every bed, as you would the books on a library shelf. 

 In a thickness of 2,500 feet, measured at right angles to the stratification, Sir C. 

 Lyell counted 19 seams of coal, varying in thickness from two inches to four feet. 



