THE ORIGIN OF UPLAND LAKES. 8ii 



every stream have filled up many a mountain pool, and frequent peat- 

 mosses mark the spot where once the waters danced in the mountain 

 breeze. Whence these hollows ? What is their origin ? Do we see 

 in them the relics of volcanic effort ? Are the combs {cwm), coves, or 

 corries in which they lie the vestiges of volcanic craters, as the form of 

 many at first, perhaps, suggests ? Or have we here hollows produced 

 directly by surface action ? Again, are these hollows of great depth, 

 or are they shallow ? What is their general form ? Now, there is 

 little doubt that most people, if asked to draw the form of the hollow 

 in which the waters of a tarn now He so placidly, would grossly exag- 

 gerate its true depth, or perhaps liken it to the basin formed by plac- 

 ing the two hands together, side by side, curved, with the palms upper- 

 most. Some years since I took a number of soundings among the Cum- 

 brian lakes and tarns, and communicated the results of my examination 

 to the Geological Society (" Quarterly Journal of the Geological So- 

 ciety," vol. XXX., p. 96, and vol, xxxi., p. 152). .Hold out one hand, palm 

 uppermost, and straighten it as much as possible — the hollow in the 

 palm is yet far too deep to represent with truth the natural rock basin. 

 Soundino-s taken in lakes throug-hout the district all show the same 

 thing — the basins are very shallow compared with their size and the 

 height of the surrounding hills. 



Next, let us search out the origin of these shallow basins. At the 

 outset we distinguish tv,'o classes of action, one of which must have 

 been at work. Either the matter formerly filling the hollow has been 

 dug out and carried away by some agent working at the surface ; or 

 force from below has here sought a vent, and dispersed the matter far 

 and wide ; or, from failing support, the ground has sunk at this spot 

 into a hollow. 



First we will consider the upward or downward theory. If these 

 numerous mountain hollows, with included tarns, be of volcanic origin, 

 then it is clear we shall find the signs of a crateral hollow such as we 

 see them in many parts of the world at the present day. There are no 

 such signs. It is true that in many cases the surrounding rocks are of 

 volcanic origin ; but the volcanic beds, in their he and position, show 

 no manner of relation to the tarn-hollows ; and a little study of the 

 rocks of the district and the form of the ground clearly shows that the 

 volcanoes which gave rise to the ashes and lavas forming many of Cum- 

 bria's highest mountains, were active, not as but yesterday, but in un- 

 told ages past. Then, as to the doionward or special depression theory, 

 when we can conceive such minute subsidences taking place at a great 

 number of almost microscopic spots without affecting the rocks around, 

 or leaving an}' evidence of a sinking away, "we may admit it as possible. 



If not produced by expulsion of matter outward or sinking of mat- 

 ter inward, these hollows must be the effect of some surface-working 

 agent. The sea planes away along the coast-line, and the material 

 goes io fill up ocean-hollows ; therefore the sea can not be the agent. 



