448 



in the neighbourhood of Bath, swell out rapidly in their north-eastern 

 course, and soon assume the same characters which Mr. Phillips has 

 assigned to them in Yorkshire. He next establishes that the whole 

 of the fine-grained white oolite in the escarpment of the Cotteswold 

 Hills, although lithologically undistinguishable from the great oolite 

 of Bath, is only an expansion of the inferior oolite. It is then made 

 apparent that the Fuller's earth disappears entirely to the north of 

 Gloucestershire j and the highest degree of interest is added to these 

 groups, by determining, for the first time, the true position of the 

 Stonesfield slate, which he shows to be the base of the great oolite; 

 thus removing it from the geological horizon, in which, from the 

 obscure sections at Stonesfield, it had before been placed. Such 

 are a few of the evidences of the good already derived from the re- 

 vision of this series of our formations by a geologist like Mr. 

 Lonsdale, who, to the eye of an unerring observer, adds the rare 

 qualifications of a thorough acquaintance with specific distinctions in 

 organic remains. 



But the value of such a work is not to be measured by reference 

 to English geology alone ; for, if it be now ascertained that the oolitic 

 groups are made up of members which inosculate with each other, 

 expanding to vast thicknesses, or thinning out entirely, within the 

 limited range of two counties ; and that even its principal formations 

 cannot be followed into Yorkshire, still less to Brora and the Hebrides, 

 without exhibiting great changes in their mineral and fossil contents ; 

 we can scarcely hope to identify each subordinate member of our own 

 country with the subdivisions of the series on the continent of Europe. 

 I willingly express this opinion, although it may seem to be slightly at 

 variance with a surmise I ventured to advance last year respecting the 

 age of the lithographic stone of Solenhofen. That comparison was 

 intended simply to afford the English geologist an approximate idea 

 of the age of a rock, which, by some of my countrymen, had been 

 considered as of- tertiary origin, by others, as belonging to the green- 

 sand ; so that if my rough estimate should prove less accurate than 

 that of a distinguished Prussian *, who has since compared it with the 

 coral rag, I shall still feel satisfied in having first pointed out to the 

 English inquirer, that the Solenhofen slate is a member of the Ju- 

 rassic or oolitic system, and that, from the general similarity of many 

 of the organic remains, such as Pterodactyli, Crustacea?, and certain 

 plants, it is probably the equivalent of the Stonesfield slate, or one 

 of the central and slaty members of this complex series. On a broad 

 scale, however, I feel persuaded, that a simple division into " upper" 

 and " lower" oolitic systems is the full extent to which we can bring 

 continental and British formations of this age under comparison. 



To Dr. Fitton we are indebted for his " Notes on the Progress of 

 Geology," in which the relative merits of the founders of the science 

 in England are well put forth ; and also for his " Geological Sketch 

 of the Vicinity of Hastings," a most valuable addition to those local 

 monographs which contribute so largely to the diffusion of precise 



* Von Buch. 



