Mr. R. Spruce on the Musci and Hepaticse of Teesdale. 195 



(in Yorkshire) and joins the Tees a little above the High Force. 

 The beautiful cascade called White Force is formed by a stream 

 which falls over Cronkley Scarr, and joins the Tees not far from 

 Winch Bridge ; here the granular or " sugar limestone " may be 

 seen both above and below the basalt : according to Professor 

 Phillips, '^ portions of the u]iper members, limestone and shale, 

 are raised up and enveloped in the Whin, which penetrates in 

 two wedge-shaped expansions between the limestones and shale." 

 The High Force is well kno\^ai to be one of the finest waterfalls 

 in England, and it is scarcely necessary to mention that here the 

 whole body of the Tees is hurled over a precipice of 63 feet in 

 height*, the lower portion of which consists of limestone and the 

 upper of basalt. 



The triangular space between the Tees, the Lune and Maize 

 beck, constituting the north-west angle of Yorkshire, is occupied 

 by a mountain range which stretches from west to east, and of 

 which Mickle Fell, the westernmost and loftiest summit, is 2600 

 feet high. Proceeding hence in an easterly direction, we come 

 successively upon Cronkley Fell, Green Fell and Holwick Fell, 

 each of which is less lofty than the one preceding, until we finally 

 descend to the eastern angle of the triangle, at the junction of 

 the Lune and Tees, which may be 900 feet above the level of the 

 sea. Cronkley and Holwick Fells terminate to the north in a 

 long and lofty range of basaltic cliffs, called " Scarrs ;" and Fal- 

 con Clints or Widdy-bank Scarr is a similar range (but with a 

 southern aspect) extending from Caldron Snout about a mile 

 down the left or Durham bank of the Tees. The mountain lime- 

 stone formation expands over the whole of this triangle, except 

 where the basalt is interposed, which it is indeed " in such 

 masses as to predominate in the general aspect of the region, 

 and give to Upper Teesdale the character of a basaltic forma- 

 tion." 



I am not aware that T gathered a single moss in Teesdale on 

 any other rock than those above mentioned, and I was from the 

 first careful to note which of the two every species appeared to 

 prefer; but it was mth some degree of disappointment I ascer- 

 tained that very few mosses were absolutely confined to either, 

 and there are not more than half-a-dozen species in the following- 

 list which I expect would obstinately refuse to grow on one or 

 other of them. Even the flowering-plants which we most usually 

 find on limestone, such as Arena aljnna and various Orchidece, 

 appear equally partial to the basalt. Helianthemum canum, which 

 is confined to the " sugar limestone " on Cronkley Fell, is per- 

 haps the only one which it would surprise me to see growing on 

 the basalt ; but as to Bartsia alpina, Elyna caricina, Carex capil- 

 * Tlie height of the fall may be a few feet less than this. 



02 



