JUKES 5 S MANUAL OF GEOLOGY. 
143 
“ These are useful terms, whether the two things be or be not related in the way of 
cause and effect. 
“ It is certain that some joints have been produced in all rocks anteriorly to, and in¬ 
dependently of, the action of the forces of upheaval which have elevated them 5 but it is 
very likely that the direction of the lines of upheaval may have been governed or modified 
by that of the principal joints, and that other -joints may have been the result of the 
action of these disturbing forces.” 
One of the best sections in the book is that on Faults; bnt it is so 
dependent on its illustrations that it is useless to quote from it, and we 
must refer the reader to the book itself. The coal-miner 5 s rule is well 
expressed by Mr. Jukes:— 
“ In speaking of the inclination of a fault, it is better not to use the term ‘ dip,’ as if 
it were a bed, but to adopt that of ‘ hade’ or ‘ underlie.’ In inclined faults, and it almost 
always happens that faults are inclined, there is one nearly invariable rale, which is, 
that the fault 1 hades’ or ‘ underlies’ in the direction of the downthrow. 
“ As a corollary of this rale also, another equally important one may be stated, 
namely, that however inclined may be the fault, no part of any bed will ever be brought 
vertically under another part of it , and therefore superior beds can never be brought by 
any fault under those originally below them. 
“ Small exceptions to these rules may sometimes occur in rare instances; when they 
do, the fault that produces them is called a reversed fault.'” 
With respect to u Reversed Faults,” the author is of opinion that 
they are always minor faults, and exceptions to the general rule of the 
same district. In this opinion we fully concur:— 
“Professor H. D. Rogers, in his paper on the ‘Laws of Structure of the more dis¬ 
turbed Zones of the Earth’s Crust,’ ‘Trans, Royal Soc., Edin.,’ vol. xxi. p. 3, in describ¬ 
ing faults along the axes of anticlinal curves, where inversion has taken place on one 
side of the anticlinal, speaks of the uninverted part of the anticlinal having been thrust 
up the inclined plane of the fault, over some of the inverted beds, as in Fig. 51. 
“ Professor Rogers does not allude to the fact of this form producing a reversed fault, 
nor is it quite clear in his paper whether the structure thus described has been absolutely 
observed in sections, or is merely introduced hypothetically as an explanation of certain 
puzzling phenomena. If actually observed, a detailed description of the locality would 
be very interesting, neither am I prepared to combat the hypothesis, if it be one, since 
it is just in such greatly disturbed districts that 4 reversed’ faults are likely to occur. 
“ Another published example of a reversed fault on a large scale is given in the Rev. 
Professor Haughton’s paper on the ‘ Mining District of Kenmare.’—‘ Journal, Geological 
Society, Dublin,’ vol. vi. In this case, also, no notice is taken of the fault, as drawn, 
being a ‘ reversed’ one; and though it is in a highly disturbed district, and running 
parallel to the axis of a synclinal curve, yet, as its plane does not coincide with that 
axis, but cuts across it obliquely, and buries some of the upper rock under the lower in a 
very peculiar manner, it appears to me a far less probable form of fault than that de¬ 
scribed by Professor Rogers.” 
Professor Haughton has recently published another example of re¬ 
versed fault on an oblique anticlinal axis, together with a general theory 
of such phenomena (“Hat. Hist. Rev.,” vol. v., Proceedings of So¬ 
cieties, p. 164, and Plate XX.); bnt we do not know whether he is 
prepared to defend the reversed fault at Kenmare adverted to by Mr. 
Jukes. 
