110 Geological Society. 



be traced, in the clearest manner, to the protrusion of trap. In some 

 cases the volcanic mounds are themselves cracked or fissured from top 

 to bottom. 



That the igneous eruptions occurred at many distinct periods, 

 Capt. Grant showed by sections, in which beds of trap alternate with 

 others of crystalline limestone, calcareous tuff, and a calcareous grit, 

 which sometimes contains angular fragments of basalt ; and by beds of 

 very different characters reposing on each other. 



Among the phenomena connected apparently with volcanic action, 

 the author described a number of mounds, varying in diameter from 

 3 to 20 yards, and covered with small tabular plates of sandstone, the 

 lines of fracture radiating, though irregularly, from a centre. In some 

 instances the summits of these little mounds having been removed, 

 a regular circle of stones appeared, inclosing an area of sandstone, 

 the fracture of the stones decidedly radiating as the stones of an arch. 

 In other instances they resembled small hillocks, from the upper part 

 of which the outer coating or tabular plates had generally fallen away, 

 and the whole consisted of a heap of broken masses of rock. 



The author then described what he considers to be a very recent 

 volcanic outburst. It is situated in the nummulitic limestone, near 

 the village of Wag£-ke-pudda, and forms a rather high flat basin, 

 or table land of about two square miles, composed of calcareous marl, 

 and flanked by low irregular hills of ironstone and gravel. The 

 sides are broken by fissures, ravines, and hollows, and the bed of 

 the basin is covered with hillocks of loose volcanic scoriae of various 

 colours. Within the basin are also several small craters or circular 

 spaces, surrounded imperfectly by walls of columnar, globular, or 

 friable basalt. These basaltic walls, however, he conceives, are of an- 

 terior date to the mounds of scoriae, which he is of opinion cannot be 

 of great antiquity, on account of the facility with which their loose mate- 

 rials are removedby atmospheric agents. Other similar outbursts were 

 also described. 



The paper concluded with an account of the Great Runn, a district 

 (exclusive of the elevated tracts called " the Bunnee and Islands") 

 of 7000 square miles. This singular region, as already described by 

 Capt. Burns, consists of a sandy flat, dry for the greater part of the 

 year, but during the prevalence of the south-west winds, con- 

 verted into an inland sea, passable however on camels. Capt. 

 Grant believes that its present oscillating position between land and 

 water, is due to an elevation of the Runn, and not to a change in the 

 level of the seaj and in support of his opinion adduced the alterations 

 both of elevation and depression of land, by the earthquake of 1819. 

 He described also several extraordinary walls of rock, thrown up ap- 

 parently by volcanic action, sometimes assuming a dome shape, at 

 others segments of circles or straight lines. 



March 8. — The reading of a paper M On the Geological structure and 

 phaenomena of Suffolk, and its physical relations with Norfolk and Es- 

 sex y by the Rev. W. B. Clarke, F.G.S., began on the 18th of 

 January, was concluded. 



The observations detailed in this memoir were made during 1827, 



