36 Reviews—Daubrée’s Subterranean Waters. 
Oxford, after Prestwich, which had already appeared on page 42, vol. i. 
a propos of the “ Phreatic Water,” is again introduced at p. 73, but it 
is difficult to say that it illustrates any ‘thing very special. Numerous 
other sections are given in illustration of the subject. Contact by 
accidents posterior to the stratification is next considered ; such as 
the accumulation of water in decomposed granite or growan, the 
granite itself being of an impermeable nature. Then, again, there 
are the phenomena presented by slips or talus, such as that shown 
at the source of the Creux-du-vent, where the spring has been dis- 
placed by a great slip on the flanks of a precipice of Jurassic rock 
(p. 98, vol.i.). There are also great accumulations of water in porous 
volcanic ejectamenta, which are thrown out in contact with more 
compact rocks. Some curious instances in Central France are given 
with plans and pictorial illustrations. Faults, of course, are well 
known to produce springs by bringing sandstones, limestones, etc., 
against clays. Such an one occurs in the neighbourhood of Loudun, 
where Mesozoic beds are represented (section, vol. 1. p. 111) as 
being traversed by a fault of considerable throw, which is vertical 
or even slightly reversed. 
The most important chapter in the book is entitled “Role des 
lithoclases de divers ordres.” M. Daubrée has a partiality for sub- 
division ; and, as we have already seen, for Greek compounds. He 
had previously given us some interesting phenomena in connection 
with faults (failles), but much the same things now figure under the 
far grander title of “paraclases.” Joints he calls ‘“ diaclases ” ; 
whilst another class of fractures, many exceedingly minute, he calls 
“ Jeptoclases.” To a subdivision of this latter, called “synclases,” 
he refers those fractures due to contraction. The whole are 
summarized under the general term “ lithoclases.” The upshot of 
all this is, that rocks are fractured in various ways, by various 
agencies and in different degrees, and of course such fissures facilitate 
the accumulation and circulation of underground waters. Under 
the general heading of “lithoclases” he appears to include the 
artificial piercing of rocks and artesian borings. 
Mons. Daubrée has now fairly settled down to his work (Role des 
lithoclases), and once more takes us through the formations in suc- 
cession, no longer dealing with the mere top-water (Phreatic) of 
ordinary wells, however deep, but showing us the mechanism of 
underground waters in its more complex phases. Considered as a 
whole the Paris basin is eminently suitable for the making of artesian 
wells. The beds there are disposed in the form of bowls of de- 
creasing size placed one within the other, the position of Paris 
itself being almost central with regard to them. These formations, 
alternately permeable and impermeable, are very slightly disturbed ; 
many levels furnish hundreds of artesian wells, whose depth varies 
habitually from 10 to 80 metres. For further particulars he refers 
to the “Guide du sondeur” by Degousée and Laurent. These 
remarks refer to the Tertiaries. and under the same heading he gives 
us an interesting account of artesian borings in the Sahara of 
Touggourt, to the south of Biskra. The first artesian wells of this 
