477 
this highly philosophical paper, he shows that these lines exactly 
correspond with the deductions of mathematical theory, resulting 
from the hypothesis of the elevation having been caused by an ex- 
pansive force acting from below upon stratified rocks, within the 
nearly elliptic area of the Wealden formation, in the S.E. of England, 
and the Bas Boulonnais. 
Prepared with the geometrical results of theory as an antecedent 
basis of his observations, aud introducing this new and most efficient 
auxiliary as a fundamental element in the machinery of Descriptive 
Geology, he has added to the views of preceding observers a ma- 
thematical precision, which forms the commencement of a new 
method of demonstrative investigation, more exact than has been 
hitherto applied to problems of such universal extent as those re- 
lating to the causes that have produced the movements of stratified 
rocks in every portion of the globe. 
Assuming theoretically the application of an expansive force 
acting uniformly upwards within an elliptic area, he finds that the 
longitudinal fissures thereby produced would nearly coincide with 
the outlines of the ellipse, forming cracks that are portions of smaller 
concentric ellipses, parallel to the margin of the larger ellipse; and 
that these longitudinal fissures would be numerous, and parallel to 
the strike of the elevated strata; and would also be interseeted per- 
- pendicularly in the direction of the dip of the strata by many trans- 
verse fissures. In all these fundamental deductions from theory, Mr. 
Hopkins finds an almost mathematically exact coincidence with ac- 
tual observation of the longitudinal and transverse fractures in the 
Weald; the former are respectively parallel to the strike of the N. 
and S: Downs which bound the area of the Wealden district, and 
are convergent to a point near Petersfield; the latter pervade 
many minor longitudinal ridges in the same district, and are most 
obvious in the well-known transverse valleys that intersect at right 
angles the chalk escarpments of the North and South Downs, form- 
ing the only outlets of the nine rivers that take their origin within 
the ellipsoid area of the Weald. 
Many of the minor transverse valleys that intersect the minor 
longitudinal ridges, give origin to perennial springs, which are 
thrown out by the dislocation of the strata, where the faults to 
which these valleys owe their origin intercept the progress of the 
subterranean waters, by breaking the continuity of the strata they 
percolate. 
From these fundamental observations, he concludes that the Weal- 
den district owes its elevation to one simple elementary cause acting 
simultaneously, and perhaps at successive intervals, at every point 
within the area in question ; and producing dislocations, not, as 
some have supposed, along one single central axis of elevation, on 
the long diameter of the ellipse, but simultaneously on many lines, 
and causing many minor elevations parallel to the curvatures of the 
margin of the ellipsoid area in question. 
The theory of the simultaneous action of the moving forces within 
all parts of the elevated area, does away the mechanical difficulty 
