1814.^ Geological Society. HSf 



have been found near Drigg. Mr. Irton had before made an un- 

 successful sinking to the depth of several feet in the loose sand, for 

 the purpose of ascertaining the termination of these tubes. Wheii 

 Mr. Greenough was on the spot last autumn the favourable state of 

 the drift sand allowing him to commence a fresh excavation at a 

 lower level than that at which Mr. Irton had been obliged to leave 

 off, he diligently availed himself of it, and the following is the 

 result. After tracing the tube in a perpendicular direction through 

 the loose sand to the depth of six feet, they arrived at the pebbly 

 beach on which the hillock stands; here the tube was found adhe- 

 rent to a pebble of hornstone porphyry, the surface of which ap- 

 peared to show evident signs of partial fusion. From the surface 

 of this pebble the tube glanced off, at first obliquely, but soon 

 resumed its original direction, and at the depth of about a foot 

 belovv the pebble was lost. Fiom these cucumstances the formation 

 of the tube is attributed to lightning. 



A paper by Mr. VVurburton relative to some beds of shell marl \n 

 Scotland, compiled from documents furbished by Mr. Lambert, of 

 Cambridge, was read. These beds of shell marl occur for the most 

 part in the sliire of Angus, and occupy shallow basons in a red 

 sandstone rock, being at present covered either by peat or by water, 

 and not uniVequentiy by both. The thickness of the marl towards 

 the centre of the bason sometimes exceeds ten feet ; biit as it ap- 

 proaches the circumference, it gradually thins out, so as not to 

 amount to more than a few inches in depth. Sometimes these beds 

 are single, in other places a succession of them is met with. The 

 peat mosses of Glamis and Forfar afford the following series, begin- 

 ning with the uppermost. Moss, containing trees, from four to 

 six feet ; shell marl, from six to seven feet ; blue clay ; shell marlj 

 nine inches; gravel or quicksand; shell marl. The marl appears 

 to consist wholly of shells of the same species as at present inhabit 

 the water by which it is covered ; namely, the helix putris, and 

 cardium amnicuin chiefly entire, and the mytillus cygneus for the 

 most part in fragments. Thus therefore the formation of calcareous 

 beds with alternations of sand and clay appears to be one of those 

 natural processes which even yet has not ceased to operate. 



An account of the Swedish corundum, by M. Swedeiistiernaj 



• was read. This mineral has hitherto been found only in the irou 

 mines of Gellivara, in Lapland, where it occurs very sparingly, 



• imbedded in a massive variety of iron glance, accompanied by red 

 felspar, red and greyish-white apatite, and silvery mica. As yet it 

 has been met with only in crystals of a light smoke-grey colour, iu 

 the form of an oblique octohedrwn, sometimes regular, but often so 

 nuich compressed as to exhibit to the naked eye only two larg^ 

 faces, the lateral ones being almost imperceptible. 'J'he size of the 

 crystals varies, from that of a pin's head to a length of three line* 

 or more. 



On the 18th February a paper by Dr. M'CuUoch, on vegstabl* 

 rtinaiiis preserved in chalcedony, was read. 



2M.i 



