On the Portland Rocks of England. 151 



hence deduced the history of the Portland " episode." The name is 

 used on the continent in a wider sense than in England ; and this 

 use was shown to be unjustifiable. After giving an account of his 

 observations on the rocks at Portland itself, and dividing the lime- 

 stones into the building-stone and flinty series, the author showed 

 that the so-called " Upper Portlandian " of Boulogne corresponds to 

 the latter, and the upper part of the "Middle Portlandian" to the 

 Portland Sand. He then endeavoured to prove by the proportionate 

 thickness, the indications of change in the lithology, and the distri- 

 bution of some of the fossils, that the rest of the so-called "Middle" 

 and the " Lower Portlandian " are represented by integral portions 

 of the Upper Kimmeridge, which are thus the " normal" form cor- 

 responding to what the author calls the "Boulognian episode." 

 The series in the Yale of W ardour has been made out pretty com- 

 pletely. The Purbeck is separated by a band of clay from the 

 Portland, and is not amalgamated with it. The building-stones 

 and flinty series are here seen again ; and a fine freestone occurs at 

 the base of the latter. The representatives of the Portland Sand 

 were considered to be older than those of other districts. 



The relations of the Purbeck to the Portland rocks at Swindon were 

 very carefully traced ; and it was shown that, while the upper beds of 

 the latter put on here some peculiar characters, the former lie on 

 their worn edges. The upper beds of the Portland, which have 

 been referred to the sand, correspond to the freestone and the base 

 of the flinty series of the Yale of W ardour ; hence the Purbecks of 

 Swindon may be coeval with the upper beds of the Portland to the 

 south. At the base of the great quarry and elsewhere in the 

 neighbourhood are the " Trigonia-beds ; " beneath which is clay, 

 hitherto mistaken for the Kimmeridge Clay ; and beneath this are 

 the true Portland Sands, with an abundant fauna new to England. 

 The limestones of Oxfordshire and Bucks were considered to repre- 

 sent the " Trigonia-heds " only ; and as the Purbecks here lie for 

 the most part conformably, it was suggested that they were formed in 

 a lake at an earlier period than those at Swindon, which are of a 

 more fluviatile character. 



Hence the Portland episode, considered as marine, was at an end 

 in the north before it was half completed in the south. 



2. " On the Correlation of the Drift-deposits of the N/VY. of 

 England with those of the Midland and Eastern Counties." By 

 D. Mackintosh, Esq., P.G.S. 



The object of the author was not to dogmatize, but to present the 

 subject in a concise form so as to stimulate to further research. 

 His scheme of correlation was founded on the horizontal continuity 

 of the deposits and their included erratics. He gave an account of 

 his discovery of the continuous extension of the upper Boulder- 

 clay of Cheshire, above a great thickness of sand and gravel, as far 

 as Berrington, south of Shrewsbury, and its appearance at intervals 

 along the Severn valley to below Worcester, where it was probably 

 represented by a bed with Malvern-hill boulders above shelly sand and 



