564: Notices of Memoirs — J. G. OoodcJiikl — St. Bees Sandstone. 



into action by the contraction of the rocky barrier by which it was 

 environed ; while the modifications produced by seismic and volcanic 

 foi'ce, together with exposure to destructive chemical and mechanical 

 agencies through long-continued periods must be taken into account 

 in endeavouring to arrive at a correct understanding of its litho- 

 logical and petrological aspects. Without enlarging on the subject, 

 it may only farther be remarked, that the thickness of the solid 

 exterior of the earth is commonly reckoned to be about 45 miles ; 

 and if we deduct 10 miles for the thickness of the stratified rocks 

 (which is practically an over-estimate, for it represents the depth 

 of all the systems, or differentiated assemblages of strata tabulated 

 iu the (;rder of time; and the series is nowhere known to exist in 

 its entirety) we have 3o miles of the crust to account for. This 

 is, properly speaking, the ' foundation ' of the earth from which 

 have been elaborated, by chemical and mechanical agency, the more 

 superficial accumulations which contribute so largely to the con- 

 venience and comfort of the human race. 



Some geologists continue to distinguish granite from the other 

 unstratified rocks by the term ' Plutonic,' and others class it as a 

 trappean rock. Its vai'ieties might more properly be described as 

 Cryptogene (of hidden origin) whatever shades of diifei'ence there 

 may be in their composition, if they exhibit evidence of a common 

 oi'igin by their position and structure ; for in granitic — let us say 

 cryptogene — rocks there are many departures from the normal type, 

 ■which consists of quartz, felspar, and mica; the hornblendic or 

 syenitic varieties forming a stepping-stone to the trappean syenites, 

 and indicating a close relationship between the two classes of 

 unstratified rocks under reference. 



L — The St. Bees Sandstone and its Associated Rocks.^ By J. 



G. Goodchild, F.G.S., H. M. Geological Survey. 

 ri^HE author reviews the history of opinion upon the classification 

 X of the New Red Rocks of Cumberland and Westmoreland, and 

 then gives the following as the maximum thickness, general succes- 

 sion, and probable equivalents elsewhere of these rocks : — 

 New Eed Series (Upper Division). 



Maximum observed 

 thickness iu feet. 



(0) Eed marls with rock salt and Gypsum 950 



(4) St. Bees Sandstone, with the following subdivisions : — 



[d) Waterstones ; (c) zone of tile red phases ; {b) dull 

 Eed Sandstone with local bands of fine con- 

 glomerate and occasional pebbles ; [a) zone of 



variegated sandstiines. In all 2000 



(4a) Graduates downward into — 



(3) Gypsiferous marls with local conglomerate at its base... 300 

 Magnesian Limestone Group. 



(2") Magnesian Limestone 25 



(2') Plant beds 150 



Lower New Eed. 



(1) Penrith Sandstone : the Brockrams L500 



1 Eead before the Brit. Assoc, Edinburgh, August, 1892, in Section C (Geology), 



