538 
THE GEOLOGIST. 
ON THE FAULTS OF THE LANCASHIRE COAL-FIELD. 
By Henry Gbeex, Esq. 
The author proposed to point out a law Avliich appears to govern the direc- 
tion of the principal lines of fault in the Lancashire coalfield, and to endeavour 
to show, on the principles laid down bv Mr. Hopkins, that this law is a neces- 
sary consequence of the forces which produced the upheaval of the coalfield. 
On the eastern and northern sides the coal-measures are bounded by millstone- 
grit, which rises conformably far beneath them. The intensity of upheaval 
along- the eastern boundary was certainly great, as might be expected from its 
proximity to the central upheaval of England, and there seems reason to believe 
that it increased in magnitude northwards. The force of elevation along the 
northern boundary seems also to have increased towards the east ; since it 
would appear that tlie north-eastern was a point of maximum elevation. On 
the south, the coal-measures pass regularly but unconformably beneath the 
Permian and New Red Sandstone formations, the boundary-line being deeply 
indented by faults, along which promontories of New Red Sandstone run up 
into the heart of the coalfield. That the portion lyiu" between the UphoUand 
and Boundary faults contains the same measures, and has been acted upon by 
the same forces of elevation as the main body of the coalfield, camiot be 
d^oubted; but its position without the basin, and some irregularity in the 
dj^rections of its lines of fault, lead the author to think that local causes have 
Cjjiefly determined tlie arrangement of the measures. It would appear that 
t e elevating forces have acted with greatest intensity along the northerly and 
Cpsterly boundaries, increasing in each case towards the north-east corner. It 
appeared also that the western boundary has been a line of upheaval of smaller 
a d more uniform intensity, and that towards the south the amount of elevation 
li s decreased to a minimum. The upheaval-area may be roughly supposed 
to be oblong in shape, its longer axis running in an east and west direction, 
and v/hile its southern and western sides remained fixed, its north-east comer 
was elevated in a vertical direction. As to the extension of lines running 
north and south across the area, it is evident that it will increase as we recede 
from the western side ; in fact, it varies very nearly as the square of the dis- 
tance from that side. In the same way the tension of a line running east and 
west will vary very nearly as the square of its distance from the southern 
boundary. Thus, over the uplifted area there will be two sets of parallel ten- 
sions, the one acting in a north and south direction nearly, and increasing in 
magnitude from west to cast ; and the other in an east and west direction nearly, 
and increasing in magnitude from south to north. The alteration in the shape 
of the area produced by its extension will make the lines of tension deviate a 
little from a northerly and eesterly direction, so that the angle between them 
will never be quite a right angle. The author had applied Mr. Hopkins's cal- 
CA.lations to the present case, and obtained the follownig results with regard to 
the direction of the first formed set of fissures : — 1. When the two tensions 
are equal, a fissure will tend to be formed in a direction at right angles to the 
line bisecting the angle between them. 2. When the tensions are unequal, in 
which the tendency to form a fissure is greatest, makes a larger angle, with the 
(.lirection of the greater tension than with that of the other, this angle tends 
to a right angle as its bisecting valve. Now, since one tension depends only 
on the distance from the M'cstern boundary of the area, and the other on the 
distance from the southern boundary, the tension will be equal when these dis- 
tances are equal. Hence, in every part on this line the fissures will tend to 
