66 REPORT— 1868. 
bable that the last point or line worn away would be the point or line on which, 
from its being in the line of centres of gravity, the upper stone would rock. 
After seeing the great Logan Stone near the Lands End, so many other approx- 
imations to rocking-siones along that coast were traced that it seemed proved, as far 
as could be expected on such a subject of inquiry, that this was a correcttheory. If 
this view were true, it seemed probable that the operations of nature might be 
hastened so as to produce artificially (if such a term may be used) the rocking-stone 
results. A very little thought suggested the experiment. Two parallelopipeds of 
iron, which had been made for keepers of magnets, were taken, similar, but that one 
was twice the length of the other. The shorter was superposed on the longe:, and 
both immersed in sulphuric acid diluted with three times its volume of water. 
Some nitric acid was added at first to hasten the corrosion. Tne liquid was 
changed from time to time as it became nearly saturated, but without changing 
the position of the iron. At the erd of three or four days the pieces of iron were 
taken out, washed, and examined, when the upper one was found to be a perfect 
analogue of a rocking-stone, so delicately balanced on two points that it could be 
made to rock by blowing on it with the mouth [result shown }. 
It was observed in this experiment that the iron rocked only in one direction, 
Such is the case with the great Logan Stone, and possibly with the greater num- 
ber of rocking-stones. It is obviously more probable that a stable equilibvium 
should be attained on two points than on one, A specimen capable of rocking or 
spinning on one point has not yet been obtained [approximation to this shown by 
two zinc disks, and explained]. Ifthe surfaces of the slates be in such close contact 
that there is not room for circulation of the saturated liquid, a formation like those 
near the Cheesewing will be effected ; or if a number of disks or slates be superposed 
and the lower ones more exposed to the weather, so as to catch the dripping and drift- 
ing water from the upper, we should get a formation exactly like the Cheesewing, 
which may be called an incipient compound rocking-stone, in that each slab is worn 
away at the edges, and the lower ones much more than the upper, so that, if left 
alone, which it will not be, and if it does not topple over too soon, which it pro- 
bably will, it might well end in a rocking-stone. Very possibly it may rock now 
in a great storm. 
On the Alternate Elevations and Subsidences of the Land, and the order of 
Succession of Strata in Norfolk and Suffolk. By the Rev. J. Guyn. 
This paper is supplementary to that read by the author at the Meeting of the 
British Association at Dundee on the “ Periodic recurrences of Oscillations of Level 
and Changes of Climature,” which may be said to have reached their maximum. 
Some of a more limited and local operation, which appear to have taken place 
during the progress of one elevation or subsidence to another, formed the subject 
of this paper. Among these the author particularized an upheayal which took 
place during the formation of the river-valleys, and may be seen at Lophamford 
in Norfolk. There the singular phenomenon of a watershed presents itself in the 
lower par% of the valley, from which watershed the Wayeney and the Little Ouse 
take their rise. A road traverses the valley descending from the high land of 
South Lopham, and leading to the high land on the opposite side in Suffolk. From 
either side of this road the water rises which forms, or rather is the commence- 
ment of these rivers, which, together with a few feet of the causeway, form the 
boundary of Norfolk and Suffolk. It is evident that, had the watershed been 
originally on this spot, the upper part of this valley (about fifty feet) could not have 
been excavated, and that the present arrangement is due to an upheaval, which 
caused the water, which had previously flowed in one direction, to flow to the east 
and to the west on either side of the watershed. A magnificent bed of valley- 
ersvel near the ford, on the Suffolk side, attests the power of the original stream, 
which is now divided and dwindled to a small rill by this oscillation of levels. 
The author next referred to the Forest-bed on the Norfolk and Suffolk coast and 
the laminated series overlying it, observing that no deposit more strikingly exhi- 
bited the effects*produced by alternate elevations and depressions than the Forest- 
bed. It was formed, in part, at least, in a basin of chalk, which was covered with 
