Geological Society of London, 231 



to the greater amplitude of vibration of the molecules of water when 

 heated; the vibrations being performed in equal times, particles 

 descending at right angles to the plane of vibration will experience 

 less resistance from the molecules of water. 



A note by Prof. Eamsay, briefly indicating some of the geological 

 -bearings of these results, was appended to the paper. 



2. " On some Fossiliferous Cambrian Shales near Carnavon." 

 By J. E. Marr, Esq. Communicated by Prof. T. M 'Kenny Hughes, 

 F.G.S. With an Appendix by Henry Hicks, Esq., F.G.S. 



The shales described by the author extend from about three miles 

 S.W. of Carnarvon to Bangor, running nearly parallel to the Menai 

 Straits. They are faulted against Lower Cambrian to the east, and 

 disappear against a dyke on the west. The shales vary from greyish 

 black to bluish black in colour, and are generally sandy and mica- 

 ceous, but in places chiefly clayey. Fossils were obtained from 

 three places on the banks of the Seiont, namely, near Point Seoint 

 (where the beds are concretionary in structure), along the old tram- 

 way from Carnarvon to Wanttle, and near Peblig Bridge. The first- 

 named locality is richest in fossils ; and here there is a greenstone 

 dyke, parallel to the bedding of the rock, and altering the shales for 

 a distance of about four yards from the edge of the dyke. The fossils 

 seem to indicate that the deposit belongs to the upper part of the 

 Arenig group. 



Appendix. — Mr. Hicks pointed out that the fauna clearly showed 

 i;hat these beds belong to the Arenig group, many of the species 

 being identical with those found in the upper part of that group at 

 St. David's, Shelve, and in Cumberland. The new species found 

 by Mr. Marr are a Caryocaris (C. Marrii) and an jEglina (A. 

 HugJiesii) . The other fossils were Didymograptus indentus, D. bifidus, 

 ■D. Murchisoni, and the var. furcillatus. Species of Barrandea, Trimi- 

 cleus, Lingula, Obolella, Discina, etc., and Orthoceras caeresiense. The 

 rock in its general character is extremely like that at the same horizon 

 in the succession at St. David's, Shelve, and in Cumberland, and 

 indicates, therefore, the prevalence of similar physical conditions when 

 deposited. The rock is such as would be formed over an even sea- 

 bottom at some considerable distance from land and in moderate deep 

 water. Mr. Hicks looked upon this discovery as of considerable 

 importance, since it clearly proved the position of beds hitherto 

 imperfectly known, and moreover shows that similar conditions pre- 

 vailed over extensive areas at the time these beds were deposited. 

 It also furnished further evidence in support of Mr. Hicks's opinion 

 that no break occurs anywhere in the Welsh area between the Cam- 

 ibrian and Lower Silurian rocks. 



3. " On the Occurrence of the Rhastic Beds near Leicester." By 

 W. J. Harrison, Esq., F.G.S., Curator of the Town Museum, Leicester. 



The sections described by the author are shown in brick-pits in 

 the Spinney Hills, forming the eastern boundary of the town of 

 Leicester, and in the Crown Hill on the eastern side of a valley 

 -excavated by the Willow Brook. In the latter locality they are 

 'Capped by Lower Lias. They have a slight dip to the south-east. 



