400 J. G. Goodchild—On “ Joints.” 
Regarded as isolated cases, such joints as these would appear to 
admit of no possible explanation but that of actual shearing of the 
rock, caused by some kind of torsion similar in its action to that 
effected by M. Daubrée’s experiments. M. Daubrée submitted plates 
of various substances to torsion, and succeeded in producing sets of 
cross fractures closely resembling joints in their mode of occurrence. 
As joints are present in every rock that will not readily change its 
lateral dimensions without fracture, no matter what the age of that 
rock, or in whatever part of the earth’s surface it may occur, the 
acceptance of this view would, it seems to me, involve the assump- 
tion that every part of the earth’s crust, through all geological time, 
has been uniformly acted upon by earth movements similar in their 
mode of action to the wrenching described in the account of the 
experiments above referred to. Whether the results of carefully- 
made observations upon the earth movements now going on lend 
any support to the view that such has been the case is a question 
I must leave for others to answer. But even if it were so, it appears, 
from the experiments themselves, that parallel sets of fissures could 
not very well be produced in this way; and even if they could be, 
it appears certain that, other things being equal, the greater the 
disturbance any given rock may have undergone, the more extensive 
should be its system of joints. Besides, every considerable change 
in the direction of the torsive force should result in the formation of 
a set of joints to correspond. So far from this being the case, the 
joints in some of the oldest, and, at the same time, some of the most 
highly-disturbed strata in the North-west of England, e.g. the Pre- 
Carboniferous rocks associated with the Pennine Faults, show 
systems of jointing certainly not a whit more complex or more fully 
developed than the joints occurring in the least disturbed parts of 
the Carboniferous rocks miles away from such zones of derangement. 
Another fact having an important bearing upon the present 
question is afforded by the disposition of joints in the case of un- 
conformable strata; especially of such unconformities as the field- 
geologist so commonly meets with in the course of his examination 
of the Paleozoic strata. Here we often find the newer of the two 
strata cleft by regular and well-defined systems of joints affecting 
them uniformly throughout a considerable thickness, and continued 
downward in many instances to the very base of the series. In 
such a case we might reasonably expect to find at least the im- 
mediately-subjacent strata affected in the same way, seeing that the 
torsive force must have been exerted through the lower set in giving 
rise to the joints that extend upwards with so much uniformity in the 
rocks above. Such community of jointing is, however, by no means 
of universal occurrence. Taking the case of the Carboniferous rocks 
of the northern part of England as an example, it is not at all 
uncommon to find the Carboniferous Limestone lying —over scores of 
square miles, almost as horizontally as it was originally deposited— 
upon a surface formed by the upturned ends of many thousands 
of feet of the Pre-Carboniferous rocks, so that the upper series, 
horizontal in its lie, oversteps a series of strata presenting a great 
