TRANSACTIONS OP THE SECTIONS. 131 



examination of the cuttings and tunnels in railroads ; and they had not of late years 

 derived more information from a single cutting than that to which he would point 

 their attention. There was a branch railway making from Bristol, from the Great 

 Western line, and which was to traverse the Severn. In making this traverse, it 

 was necessary to cross a ridge of limestone near Almondsbury, the railroad cutting 

 through the carboniferous limestone. In one part strata were subject to very great 

 contortions. In some parts there were broken bands of coal, thrown about in an 

 extraordinary way. The whole of the highly inclined strata were sm'mounted by 

 new red sandstone. It was remarkable that there was in this cutting an enormous 

 amount of calcareous and other grits which seemed to form a reg-ular part of the 

 mountain limestone. There were also large red masses, evidently formed by con- 

 cretion. 



Sir R. Murchison exhibited a detailed diagram prepared by Mr. Richardson, 

 and, having visited the^locality, explained the chief phenomena to the Section, 



g remising that the tract should be examined carefully by one of the Geological 

 urveyors. 



On the Nature of Sigillariffi, and on the Bivalve Shells of the Coal. 

 By J. W. Saltek, A.L.8., F.G.S. 



The object of the communication was to describe some specimens of Sigillaria 

 which have the appearance of having grown in water, inasmuch as they have the 

 stem swelled at short intervals, and show scars like those of the rootlets of Stig- 

 maria at these swollen varices. The scars in question appear between the ridges on 

 which the rows of leaf-scars are arranged, and tenninate where the swelling ceases. 

 Such swellings are seen in several fine specimens, in the Manchester Museum, of 

 Sif/. (Fari(hiria) tes.iellata, S. nodosa, and S. hexagona. 



That the Sigillarue gi'ew in water has long been the opinion of Mr. Binney (1840), 

 and (independently) also of Professor H. Rogers (1842). The tracks of large 

 worms in the sediment, the spiral annelides {Spirorhis), and the very frequent in- 

 termixture of undoubted sea-shells, have led the former author to speculate freely 

 on their growth in sea-water. And the presence of verj' salt water in coal-mines, 

 and of soda in all coal, as Dr. Percy affii-ms, is a confirmation of this belief. 



The freshwater character of the coal-gi-owths has been assumed chiefly fi'om the 

 occurrence of shells like Unio in it (Anthracosia of King). These, however, differ 

 in some important particulars from true Unio, and they are foUnd associated with 

 shells {Anthracomya) which appear, from their wrinlded epidermis, to be related 

 to the MyadcE. They occur, too, though much less frequently, with true marine 

 forms, Prodiictus, Spirifcr, &c., in the ironstones ; and one, the common Anthra- 

 cosia acuta, is even found in the moimtain limestone shale, where the fossils are all 

 marine. 



On the Granitic RocJcs of Donegal, and the Minerals associated therewith. 



By R. H. Scott, M.A. 



The author gave a short account of a mineralogical tour made by him, in com- 

 pany with Professor Haughton, in the course of the smnmer, the results of which 

 seemed to throw some light on the possible origin of granite. The district visited 

 was Donegal, which county consists mainly of gneiss and mica-slate, and is traversed 

 in a N.E. direction by an axis of granite. This granite is of a peculiar composition, 

 containing two felspars, one orthose, and the other, not albite, as in the granite of 

 the Mourne mountains, biit oligoclase — a mineral whose occurrence in the British 

 Islands had only been noticed within the last twelve months. Professor Haughton, 

 to whom this discover}'^ is due, was unfortimately unable to attend the Meeting. 

 The facts were briefly these : — The granite contains oligoclase and quartz, which 

 combination appears to be a proof that the rock never was in a melted condition, 

 as in that case these two minerals woidd have acted on each other and formed com- 

 mon felspar. It lies in beds corresponding to the general lie of the strata of the 

 country, and in its character is essentially gneissose ; and, lastly, at points inside 

 the area of the gi-anite, metamorphic rocks (limestones and slates) are foimd with 



9* 



