276 



age ; and even those geologists who most strenuously support the 

 so-called uniformitarian doctrines, incline to attribute the peculiar 

 position of the coal to one of those great inversions of the strata so 

 frequent in highly disturbed districts of all ages, from Palaeozoic up 

 to Tertiary times. 



The fourth paper commences with a succinct sketch of the general 

 geology of Portugal, and goes on to define the limits of the secondary 

 rocks north of the Tagus, both by stratigraphical and palseontological 

 evidence. Long before this paper was read, Mr. Sharpe had 

 acquired much critical skill and knowledge as a palaeontologist, and 

 on palseontological principles he now established the existence of 

 Cretaceous and Jurassic rocks in the country described. The whole 

 formed an excellent sketch of a hitherto undescribed country, and up 

 to this date British geologists are chiefly indebted to these memoirs 

 for the knowledge they possess of a land where the science is almost 

 uncultivated. 



Between 1842 and 1844 Mr. Sharpe gave four memoirs to the 

 Geological Society on the Silurian and Old Red Sandstone Rocks of 

 Wales and the North of England, territories previously chiefly illus- 

 trated by the labours of Professor Sedgwick. The first of these is 

 "On the Geology of the South of Westmoreland." Part of this 

 paper describes the range of the Coniston limestone. Mr. Sharpe 

 identified it by its fossils as forming part of the Lower Silurian series, 

 but did not determine its actual horizon. In 1839 Mr. Marshall 

 placed it on the parallel of the Caradoc sandstone, which determina- 

 tion the researches of later geologists have sustained. 



Mr. Sharpe also pointed out the unconformity of the Upper on 

 the Lower Silurian rocks of the area ; and in describing the passage 

 of the Ludlow rocks into the Old Red Sandstone, he correctly infers 

 that the Tilestones of South Wales should be withdrawn from the base 

 of the Old Red Sandstone and classified with the Ludlow rocks, to 

 which their fossils unite them. At a later period of the same year 

 he produced a memoir " On the Bala Limestone, and other portions 

 of the Older Palaeozoic Rocks of North Wales." Up to this date it 

 was believed that at Bala and elsewhere there was a great thickness 

 of fossiliferous Upper Cambrian rocks below the Lower Silurian 

 strata. Mr. Sharpe maintained that this was an error, and that both 

 stratigraphically, and by their fossils, the Bala rocks were the equi- 



