1820.] Royal Academy of Sciences. 215 



The base of Leigh and Weston Down, and the valley situated 

 between them and the Avon, are, for the most part, covered with 

 .horizontal strata of magnesian conglomerate. 



The west boundaiy of the main coal field is continued on the 

 other side of the gorge of the Avon in the calcareous chain that 

 winds round the south-east and north sides of the vale of West- 

 bury, and constitutes Durdham Down, Henbury, and Kings 

 Weston Down. The fundamental part of this valley is old red 

 sandstone, the truncated edges of which are, for the most part, 

 covered by horizontal beds of magnesian conglomerate; the dip. 

 of the old red sandstone and hmestone is outwards in every direc- 

 tion from the axis of this valley. 



The next group of mountain lime and old red sandstone along 

 the west frontiers of the main coal field is that which extends 

 from the ridgway near Almondsbury to the village of Tort worth, 

 and which dips regularly towards the interior of the coal basiu 

 with a fe\w partial exceptions. 



The intermediate space between Almondsbury and the West- 

 bury group shows only beds of the lias and young red sandstone 

 formation, which on this side intrude largely within the coal 

 basin, extending to Stoke Park, on the edge of the Kingswood 

 collieries, and, in all probability, covers up considei-able tracts 

 of coal ; this Has seems to have been once connected with that 

 of Pucklechurch and Sodbury, covering the whole South Glou- 

 cester coal, from which it has been since partially removed by 

 denudations. 



AtTortworth the calcareous chain of the west frontier reaches 

 the point where it is suddenly deflected southwards at an acute 

 angle, and from which it may be traced with certain interrup- 

 tions along the east frontier of the great coal basin to the 

 Mendip hills, near Mells. 



Near Tortworth, beds of transition lime are protruded from 

 beneath the old red sandstone, and are intersected by two dykes 

 of trap. We also find there a few traces of coarse greyvvacke 

 slate. 



ROYAL ACADEMY OF SCIENCES AT PARIS. 



An Analysis of I he Labours of the Roi/al Academy of Sciences 



during the Year \H18. 



{Continued from p. 65.) 



Reports apvkoved of by the Academy. 



Experimental Researches upon Lime for Building ; by M. 

 Vicut. — As the whole of this important report will be printed in 

 an early volume of the Memoirs, we shall now only transcribe 

 the conclusion of the report of the committee, Messrs.de Prony^ 

 Gay-Lussac, and Girard, Secretary. 



" This vvork engaged the attention of your Commitiee both on 

 account of the new facts itctntains, and the order and clearness. 



