132 Charles Maclaren, Esq., on the Existence of 



" erratic blocks." Their appearance is one link in the chain 

 of evidence by which the ancient existence of glaciers in cer- 

 tain localities is established. 



I did not see any distinct traces of lateral moraines at Gare 

 Loch ; but the chance of finding these should be greatest to- 

 wards the foot of the loch (for they increase in size as they 

 descend), while my observations were chiefly confined to the 

 head. Agassiz states that they are often indistinct, and 

 enough has been said to show, that their non-appearance 

 now does not prove their non-existence at a former period. 

 I may remark here, that the gentler declivities on the sides 

 of the loch are generally covered with a coat of sandy clay 

 mixed with pebbles, from a foot to two yards in depth, which 

 may possibly be tlie wrecks of lateral moraines. But farther, 

 there are markings on the surface of the north-east part of 

 the valley which deserve notice in reference to this subject. 

 They are best seen from the road near b. On looking east- 

 ward from this point, the eye observes something resembling 

 a series of terraces on the opposite declivity. They are 

 marked ^ ^ in the map. When we place ourselves on or 

 among them they are less distinct, but most of them are still 

 recognisable. They are not exactly parallel to each other, 

 and neither are they truly horizontal ; for most of them have 

 a slight inclination southward. They reminded me of lateral 

 moraines ; but I could not satisfy myself that in form and po- 

 sition they had the character which these ought to possess, 

 though they seemed evidently to have been impressed on the 

 surface by some external agency. It must be kept in mind 

 that, except a few prominent rocks, the whole surface of the 

 declivity here is covered with peat or turf. 



But if distinct traces of moraines are wanting, erratic 

 blocks are numerous. A large proportion of these are of 

 mica-slate, the rock of the district, and may have come only 

 a short distance, but when of great size (six or eight cubic 

 yards for instance), and found resting isolated on a bed of 

 gravel and clay, on ground little inclined, and remote from 

 any precipice whence they could fall, they are still travelled 

 stones, and must have been brought to the places they occu- 

 py by some agent which no longer operates. There are 



