288 GENERAL OBSERVATIONS. 



series reduced within a small compass, and ready to vanish. Analogy 

 would therefore lead us to think, that each stratum may have originally 

 been a kind of flat lenticular mass, wearing to a thin edge on every 

 side. It has been justly observed by some authors, that the crust of 

 our globe is rather to be described as squamose, like an artichoke or 

 the root of a lily, than tunicate, with concentric coatings, like an onion. 

 The notion of universal formations, or of rocks of any one kind that 

 have completely enveloped the globe, is not borne out by the facts 

 before us. Some of our strata may indeed be traced in certain directions 

 to a great extent; particularly the chalk, the oolite, and the aluminous 

 strata with their lias seams : but as we find them all wedging out on 

 some of their sides, and other strata doing the same on all sides, we may 

 reasonably presume, that these more extensive masses, if traced out, 

 would be found to terminate in a similar way. The chalk strata 

 I'each, with some interruptions, from Flamborough Head, to the south 

 of England ; and are found to extend into France, and other parts of 

 Europe; but though we should suppose the whole to have once 

 formed a continuous mass, which is by no means certain, it does not 

 follow, that these strata once encircled the whole globe. It is true, 

 that the strata of our chalk hills, and those also of the oolite and 

 alum hills, leave off so abruptly on some of their northern and western 

 fronts, as to make it evident that they must have extended much 

 further to the north and the west: yet we have no right to infer, 

 that all or any of them have ever reached the Pentland Firth, or the 

 Hebrides, The magnesian limestone may have stretched much further 

 than it now does, over the coal measures of Durham and perhaps of 

 Northumberland ; the red sandstone, if it be not a mere iipjilling, 

 may have extended a great way over the magnesian limestone; the 

 aluminous beds and lias seams may have reached far over the red 

 sandstone; and each of the succeeding members of the series might 

 spread out in a similar way; but each of them, we may presume. 



