224 APPENDIX. 



more properly be called gravelly and sandy. It contains 

 many cells or cavities, some of which are filled with crys- 

 tallizations of carbonate of lime : much white hornstone 

 appears disseminated throughout the mass. The hornstone 

 is sometimes seen to constitute small beds or layers from one 

 to three or four inches in thickness, which are continued for 

 several feet in length ; frequently also appearing under the 

 form of flattened irregular nodules lying in an almost con- 

 tinuous line for a considerable distance, and with their long 

 or flattened side parallel to the stratification ; resembling in 

 this respect the disposition of the clay-iron stone in the slaty 

 strata that accompany the bituminous coal. Organic remains 

 are by no means uncommon, though they are not found as 

 abundantly as in some other spots of our route. They con- 

 sist of terebratulites, encrinites, and a madreporite (Linne) ; 

 the true nature of the last of these could not be ascertained 

 without a comparison of characters, which we were unable 

 to make on the spot, and which the loss of all the specimens 

 collected between Fort Wayne and Fort St. Anthony, has 

 prevented Mr. Say from making since ; the rock is of a 

 greyish yellow color, with a loose structure. We are aware 

 that some of the characters which we have given of this rock 

 might lead to the opinion that it resembles the mountain or 

 carboniferous limestone of Messrs. Conybeare and Phillips ; 

 and consequently that it is the same as the metalliferous 

 limestone of other geologists ; but we would consider this 

 opinion as a very hasty, not to say, an incorrect one. Although 

 its cavernous nature, its indication of crystallization, and its 

 organic remains, present an apparent correspondence with 

 those of that limestone as described by the Rev. W. D. 

 Conybeare in the excellent ' Outlines of the Geology of Eng- 

 land and Wales' (part i., p. 353), we incline to the opinion 

 that this rock is of a much later formation ; we believe it to 



