James Geikle — On the Aye of the Croflhead Deposits. .05 



that tlic force wliich Bqnoezod and puckcrod thorn must liavo acted 

 in a direction down and not across the valley, MorO(jvor it is a fact 

 that the similar intercalated beds of clay, sand, and silt, so commonly 

 met with in the Lower Boulder-clay of Scotland, almost invariably 

 show contortions in the same manner as here. 



5. An examination of the slope of the f^ronnd above the spot 

 where the mammalian remains were found, ccrtaiidy does not favour 

 the idea of a landslip having taken place. The accompanying 

 section (Fig. 1), drawn on a true scale, will better show this than 

 mere verbal description. I have represented here the original sur- 

 face of the ground before the railway operations were begun, and 

 the line of section crosses the valley a few yards below the spot 

 where the skull of the great ox was got. From B to A the general 

 slope of the hill-side is not more than 11° ; and from A the hill 

 continues to slope up at the same angle for a distance of 470 yards, to 

 Avhere the hill-top is reached at a height of about 725 feet above the 

 level of the sea. At B the rock-surface suddenly dips down at a 

 much steeper angle, and against this slope the stratified beds abut. 

 The Boulder-clay which rests upon these deposits originally extended 

 as far as c, but was subsequently removed during the progress of the 

 railway cutting. Now if the overlying position of the Boulder-clay 

 is supposed to be due to a landslip it will also be necessary to sup- 

 pose that the Till in question has glided bodily down a long gentle 

 slope of 11°, that it has performed this wonderful feat of agility 

 without leaving behind it any portion of its substance, and that after 

 toppling down the slope at B it has crept boldly on over the level 

 surface of the 5os-beds for a distance of at least 150 feet ! ^ 



6. As the Boulder-clay which, overlies the ^os-beds at the place 

 from wliich the section (Fig. 1) is taken is the same deposit as that 

 beneath, which th.e stratified clays, etc., re-appear some little distance 

 further up the valley, it follows that, if at the former place the 

 overlying position of the Till be due to a land-slip, then the same 

 must be the case here too. Upon such a supposition we have to 

 believe that the Boulder-clay has slid along a slope of 12° for a 

 distance of 230 feet at the very least, or if we suppose it to have 

 come from the flat hill-top then it must have glided along the same 

 gentle slope (12°) for some 660 yards or thereabouts. After this it 

 must have had sufficient impetus to carry it for a distance of about 

 230 feet over the nearly level surface of the underlying lacustrine 

 deposits ! 



But the accompanying section (Fig. 2) will show more clearly the 

 nature of the ground. The general slope of the hill-side, above the 

 Boulder-clay terrace, &2, is, as I have just stated, only 12° for a 

 distance of 660 yards to the highest point [725 feet above the sea], 

 overlooking the valley at the place from which the section is taken. 

 The slope is quite bare of Boulder-clay. At &2* a small patch of 

 Boulder-clay is represented, which by this time may have been 



^ I liave not represented mucli of the south-east slope of the valley, as I do not 

 suppose any one will dream that the Boulder-clay has slid from that quarter. 



