378 
THE GEOLOGIST. 
Here allo\v iiic io remark (hat g'ypscous deposits liaiipcninjr to possess a more 
lliau very slif^ht degree of solubility, would uot cutii-ely sink in passinp; from 
tlie base of dccoiiiposiiif^ limestone fissures, and there would be formed layers 
of fresh water on the now concentrated salt (a truth still noticeable at sea), 
and the supply of gypsum yet going on whilst evaporation from the surface of 
the fluid layers still proceeded, there would thus be formed beds of rock salt 
which alternate with gypsum. 
During the progress of these changes, abundant herds of chambered nautili 
and other cejihalopods are sporting in the quiet waters; and whilst the atmos- 
phere is now becoming purified for the reeejition of air-breathing birds and rep- 
tiles, the traces of whose footprints on the sands are even undisturbed by the 
gently rippling waters, the truly igneous rocks are on the eve of pouring forth, 
their lavas, which (as Pownes has shown) contain phosphoric compounds, these 
being more abundantly required for the purposes of the seed-producing plants 
and the supply of bone ; and whilst the reptiles of the Lias are by such dis- 
tiu-bing causes frequently destroyed, and the delicately sculptured trilobites 
have entirely disappeared, the agitated waters, charged with our bicarbonates, 
deposit oolitic rocks, by reason of the numerous shitting grains of sand. Just 
before the close of these commotions there may be remarked another change, 
resulting probably (as may be clearly shoM'n from causes now operating in the 
mineral veins of Cornwall and elsewhere), from the accidental presence of fluo- 
rides in our decomposing limestone strata (comparable, perhaps, to those of 
Derbyshire with veins of fluor-spar), green compounds, differing from mere 
siliceous sand, and somewhat allied in composition to chloritie rocks, mingling 
their contents with the settling products. And, now again, there is a period 
of rest, and whilst the draining of an upraised or still existing westward con- 
tinent is pouring forth torrents of clayey mud, our bicarbonates deposit ehaUty 
rock, which, with the innnensely numerous remains of microscopic shells and 
corals, cover the ocean's bed, and at intervals in which organic forms are 
favourably found for nucleus, there are formed on it siliceous nodules, in a 
manner similar to that in which the fossil stems of trees sibcify, and compara- 
ble in this respect with the septaria from our shales and ironstone nodules from 
the Gaidt. Changes still go on, and during these there forms a separating gulf 
between our Gaubsli neighbours and ourselves, and at the same time sink the 
basin-shaped foundations for their capitals, and where these now stand, strange 
pachyderms, huge snakes and crocodiles in groves of palms, with monkeys, have 
theii" sway ; but by-and-bye pouring forth of rivers charged with sulphuric acid 
from the decomposing iron pyrites of the rocks, and similar to the so-called 
" vinegar river" of Columbia, at the present time, rashing with \'iolenee into 
these, react upon their loose calcareous strata, decompose their shells, and over- 
throwing the adjacent banks, bury their mammals in a gypseous mass, dislocat- 
ing their fragile skeletons, and often leaving only parts of them. To such suc- 
ceed still more gigantic pachyderms, and very soon manmioths, rhinoceroses, and 
hippopotami, our varied mammals of the caves, with lions, bears, hyanas, 
wolves, the maehahodus, and other flesh-eonsumiug animals fitted to cope 
with them, hold their reign; but all this whife an elevating action (perhaps 
resulting from the same causes that overwhelmed the ancestors of these pre- 
daeeous tyi-auts), has been in operation, raising whole moiuitain chains — 
the Alps, and Pyrenees, Carpathians, Himalayas — having their lofty peaks 
crowned with the nummnlitic limestones, and to this again succeeds, through 
chemically undcrniming influence upon the rocks, a period of swift depression, 
during which the crags were formed through stormy waters lashed into fury by 
the raging winds, commencing now to change and modify the tainted air, and 
fit it for the dwelling of a future human race. 
But during, and, indeed, before this time, the smouldering volcanos have 
