THE LOCH LOMOND AND OTHER VALLEYS. 213 



the main fault ; while the deepest spot in the basin 

 (105 fathoms) seems to be at the junction of the main 

 and Culness valley faults. We have now stated the 

 principal facts in connection with this lake-basin, and 

 proceed to offer suggestions as to its formation. 



If this valley were solely due to rain and rivers, it 

 would necessarily deepen gradually from its upper to 

 its lower or south end ; this, however, is not the case.^ 

 If due to the erosion of ice, the deeps and shallows 

 ought to graduate one into the other, and have a 

 trend conformable with the lie of the valley, and 

 consequently with the course of the glacier; this, 

 however, is contrary to facts. Again, marine action 

 could not possibly have excavated this valley ; on the 

 contrary, it would tend to fill it up; but the extreme 

 shallowness of the lower or south portion seems not 

 to be due to such a cause, as the soundings record a 

 rock bottom in many places. It should, however, 

 be pointed out, that in some of 'the neighbouring 

 fiords, such as Loch Fyne, there are extraordinary < 

 deeps in the upper portions, which apparently are not 

 being filled up by sea action. 



It has been shown that the valleys and depressions 

 at the surface are connected with breaks in the strata, 

 while the bearings of all the deeps in the lake-basin 

 are similar to those of the features in the adjoining 

 country, or they have a relation to the several junc- 

 tions of the transverse valleys with the valley of Loch 



