336 
rate of upheaval over all portions of the surface of the globe, 
during all ages ! Such is a grand instance of conjectural 
chronology as given by one of the greatest of geologists. ■ 
As another instance, I take the following from the same 
high authority; in this case, an estimate of time required lor the 
growth of strata. A mass of rock, sixty feet thick, is described 
as composed of layers so thin, that “ thirty are sometimes 
contained in the thickness of an inch.” Observe the some - 
times;” for we notice in the same description, that there are 
“occasionally ” layers of flint, carbonaceous matter and marl, 
each, as it seems from the statement, “ about an inch thick. 
We have no means given of estimating the “ sometimes, nor 
the “occasionally,” that are manifestly of so much importance 
in the case. Between the layers, of which thirty occupy an 
inch, there are marks of plants that have been flattened and 
carbonized, and “sometimes myriads of small Paludmce and 
other fresh-water shells.” Here again we observe the some- 
times.” For these thin leaves are spoken of as each • a page ot 
history representing a certain period of the past. Anc we 
are evidently expected to draw the inference that these jocks 
that have grown in ancient lake-bottoms, were formed with 
extreme slowness.” We are also told that masses of the same 
sort of rock, two hundred feet thick, are found m the neigh- 
bouring hills . t Well, how shall we calculate? Say that wc 
give each bed of shells a year to grow, and forget the some- 
times/' and the “ occasionally ” also. One inch of rock gives 
thirty years ; a foot of rock, 360 years ; sixty fee , - , y eais ; 
200 feet, 72,000 years ! Here, then, is a magnificent idea. 
But what if a bed of such very small snail-shells should not take 
a month to grow ? What, if some of the flattened plants might 
be floated and laid on the surface of the lake-bottom every 
day ? What, if the heat at noon and the cold at night, attect- 
incr the muddv water, might account for the layers . Bach ot 
them would then represent but a day, and thirty of them only 
a month. What if the “ sometimes," in which the snail-shells 
occur, should be very few times, and the * f occasional y, 
which qualifies the occurrence of layers an inch m thickness, 
should be really very often. How do our /2,000 years dwmd e 
down into a very brief period indeed ! If we take for example 
any pond into which muddy streams are flowing, it is surely 
anything but according to experience and observation among 
those who should clean such places out, that they take ages o 
* Lvell’s Antiquity of Man , edition 1863, pp. 58, 178. Sir Charles 
advances this two-ania-half-feet -scale in exceedingly cautious language, Lut 
argues 
t Lyell 
upon it as if it might he fairly assumed, 
yell’s Elements of Geology , edition 1865, ; 
page 229. 
