264 Marcel de Serres oi the Old World 
fluential cause in the formation of mountains has, doubtless, been 
the raising up of the ground, whether it took place from the ex- 
pansion of elastic fluids, or was produced by some other action. But 
these causes have not acted alone. Others, though less powerful, 
have also modified the relief of the earth’s surface, and given it the 
form which now meets our eyes and invites our observation. 
Nore 15. M. Hericart de Theury thought that waters ready to 
burst forth might be found, at Grenelle, in the lower beds of the 
chalk, and that, as they would be fed by the same aquiferous reser- 
voirs found at Rouen and Tours, they would be met with at a 
depth of 560 or 575 metres. He estimated, moreover, before the. 
wells at Grenelle were sunk, that the waters would spout out at 15 
or 20 metres below the surface, and that they would be abundant and 
of good quality. These predictions of M. Hericart de Theury were 
verified almost to the letter; instead of being obliged to dig to 560 
metres, the sheet of water was found at 547. It has furnished spout- 
ing springs which, when the probe-hole was furnished with a tube, 
rose to a height of nearly 30 metres. On the other hand, Mr Wal- 
ferdin had calculated that the aquiferous sheet was to be found in 
the neighbourhood of Tours, at 125 or 130 metres below the level 
of the sea, and that the waters would be ejected at Grenelle when 
the probe should reach the corresponding sheet. This calculation 
is as well verified as M. Hericart de Theury’s predictions. 
Norte 16. The Portland deposits, which belong to the secondary 
epoch, are the earliest formations in which animal species were dis- 
covered whose analogues now live in fresh or salt waters; both 
have the closest affinity, not in regard to their specific relations, 
but in their generic characters, to living races. It is only in the 
time of the tertiary deposits that the distinction of fresh and salt 
water species becomes decided, and when the lacustrine formations 
have covered spaces of pretty considerable extent. Before the Port- 
land and Wealden formations, the nature of the deposits, and even 
the organization of vegetables and animals, present no character 
which enables us to recognise differences in the waters where the 
one or the other lived. : 
Nore 17. When we say that there existed, in geological times, 
lizards as large as whales, we do not mean to compare these ani- 
mals in regard to bulk, but only in respect to their length. We 
could not, in fact, establish a comparison between them, and place 
them beside each other in the first point of view, as will readily be 
seen when we consider that most lizards are provided with a tail, 
whose length equals that of their body, and that this part never 
acquires a great breadth, and consequently a volume, above certain 
dimensions. 
Nore 18. According to the enumeration we have given, the 
ancient vegetatiun was only a fiftieth, or at most the fortieth, of the 
present vegetation. The former appears to have acquired, in Europe, 
a ae 
