528 Correspondence — Mr. C. Callaway. 
be complicated by a local upbeaval of soraewbat horizontal strata 
into a curve or arch ; that then, while still upheaved and so distended 
laterally, a subsidence may take place towards the crown only of the 
arch, letting down the keystone, so to speak, as a ‘ trough ’ fault ; 
then, on an extension of the same subsidence over a larger area, the 
arch, being keyed up afresh by the occurrence of the trough fault, 
can only give way by rupture of the nature of an overlap or reversed 
fault. These overlaps are sometimes on a considerable scale. Within 
a few miles of the place whence I write, there is a well-defined and 
proved and, as it happens, easily measured fault of tliis kind, in 
which the amount of movement is no less than 101 fathoms mea- 
sured in the plane of the fault, the amount of throw being seventy- 
four fathoms vertical, and about sixty-nine fathoms horizontal. The 
hade of this fault is very nearly the same as Mr. Hebert’s experi- 
mental ones, being 47°. I would also call attention to the fact that 
the downward vertical pressure P (vide liis diagram) can in no case 
exceed the actual simple weight of the mass above the fault, and 
that in actual nature it is impossible (vide Fig. 2) for the left-hand 
portion to subside unless there be roorn for it to subside into. This 
room can, generally speaking, only be got by the horizontal 
Separation of the masses on both sides of the portion subsiding. It 
would thus appear probable that all direct faults are of the nature 
of trough faults, that is to say, that either near or far off there is a 
somewhat parallel fault with an opposite hade, contemporaneous as 
to date of occurrence, and that this pair of faults meet sooner or 
later in deplh. I would thus suggest that in the case of direct 
faults Mr. Hebert should in bis inference substitute horizontal 
tension for vertical pressure (which is a secondary effect), and that 
the rule should be stated thus : — direct faults are indicative of 
horizontal tension, reversed faults of horizontal pressure. 
Ston Easton, ne ak Bath. H. E. H. 
PROF. MANTOYANI AND TUE < MIOLITHIC ’ PERIOD. 
Sir, — Prof. Mantovani, in your last issue, proposes the term 
“ Miolithic ” for a period intermediate between the Palaeolithic 
and the Neolithic. The term appears to be formed upon the 
“ Miocene ” of Lyell, which, of course, does not mean Middle 
Tertiary. Should the Italian Professor establish his new period, 
he would more appropriately substitute “ Mesolithic ” for “ Mio- 
lithic.” It is to be presumed he uses his terms in a purely local 
sense, for his Italian Miolithic age is represented as being con- 
temporaneous with an age which produced “ beautiful vessels of 
perfect work, resembling those of the ancient Etruscans,” and was, 
therefore, probably post-lithic. Tlie teachers of our Science should 
not forget, for the sake of beginners, that the words Palmolithic,” 
“ Neolithic,” etc., represent, not absolute epoehs of time, but stages 
in human development. Charles Callaway. 
Wellington, Salop, 
Oct. 4 t/i, 1Ö77. 
