TRANSACTIONS OF SECTION C. 473 
6 
approximately given by the equation Ve >in which V=velocity of ripple in 
feet per hour, and v mean velocity of current in feet per second. The volume 
of sand moved per hour along a strip 10 feet wide is shown to be approxi- 
mately =0°0476 v° cubic feet; that is, within the limits of the experiments, the 
volume of sand moved varies practically as the sixth power of the mean velocity 
of the current. 
This result differs slightly from D. F. Deacon’s1; he states that the weight 
of sand moved was proportionate to the fifth power of the surface velocity, 
possibly a little more. The practical importance of the experiments lies in being 
able to deduce from the velocity of the current the quantity of sand being 
moved along the bottom. E 
6. On the Recent Harthquakes. By Dr. J. Mune, F.R.S. 
7. On Buckled Folding. By G. Barrow. 
A number of descriptions has been published of portions of areas of 
regional crystalline metamorphism in which the dip of the bedding, or in some 
cases the dip of the foliation, is described as being at a low angle over a con- 
siderable area. These descriptions are at times so worded as to convey the 
impression that this represents the original and but slightly disturbed bedding 
of the altered sediments. Experience is gradually proving that the altered 
sediments in such areas are always intensely folded, and the detailed examina- 
tion of the Highlands suggests that in place of these long-continued low dips 
being due to small disturbance, they really represent the most complicated 
form of structure, for which the name of ‘buckled folding’ is suggested. 
The best-known illustration of the phenomenon in this country is afforded 
by the gneissose-flagstones or Moine gneisses. The deceptive nature of the dips 
in the rocks was soon recognised by the officers of the Geological Survey of 
Scotland, who found that in cliff sections the beds really ascended the clifis by a 
zigzag course, to which the term ‘lightning-structure’ was applied. 
The mode of production of this ‘ zigzag’ structure can be traced on the cliffs 
between Stonehaven and Muchalls, in Kincardineshire. The rocks in these cliffs 
consist of alternations of grits, gritty shales and shales, becoming more and more 
crystalline as we proceed northward. Nearer Stonehaven the bands of grit may 
be seen to ascend the cliffs in an unbroken or unbent course from bottom to top, 
having a high dip in a northerly direction. The limbs of the folds are thus 
isoclinal and unbent. But as we proceed northwards the course of the grit 
bands up the cliff face is no longer straight; a small overfold or ‘buckle’ is 
developed on it. At first only one is seen in the whole height of the cliff; 
further north two occur; then three, and so on, till at last they are so close 
together that the still straight portion of the fold is little, if at all, longer than 
the ‘ buckled’ or overfolded portion. If the upward course in the cliff of each 
grit band be carefully followed it will be found that the oncoming of this 
‘buckling’ structure’ does not alter the dip of the band as a whole; it still 
ascends at much the same angle, only it pursues a more zigzag course. The 
overfolds or buckles all face the same direction right up to Muchalls, and a little 
consideration will show that this ‘buckling structure’ must have been pro- 
duced after the isoclinal folding was completed. There is thus no evidence to 
suggest that the rocks in which the buckling structure has been developed 
should be separated as a different series from those in which it does not occur. 
In the interior of the south-eastern Highlands this structure is present in all 
but the southern margin of the area, till we reach the first outcrop of 
the Highland quartzite, where the buckling rapidly ends and the earlier 
isoclinal folding is left unaltered. For a distance of some seven or eight miles 
the buckling structure is either very rare or absent, but it sets in again in the 
quartzite close to Braemar. It is there also shown both by the marginal sandy 
beds, known as the Moine gneisses, and the dark schist next them. There 
also is no justification for separating the beds with the superinduced ‘ buckling 
1 Min. Proc. Inst. C. H., 1894, vol. 18. 
