n the water, and the area and depth
of the delta, and says it must have taken sixty-seven thousand years for
the formation of the whole; and if the alluvial matter of the plain
above be two hundred and sixty-four feet deep, or half that of the
delta, it must have required thirty-three thousand five hundred years
more for its accumulation, even if its area be estimated at only equal
to the delta, whereas it is in fact larger.[369] He makes no allowance
for tidal deposits.

But Brig. Gen. Humphrey, of the United States Surveying Department,
goes over Lyell's calculations, and shows that instead of 3,702,758,400
cubic feet of mud brought down by the Mississippi, as estimated by
Lyell, the actual amount is 19,500,750,000,000; that the rate at which
the delta is now advancing into the gulf is fifty feet per annum, and
that the age of the delta and alluvial deposit is four thousand four
hundred, instead of Lyell's one hundred thousand five hundred
years.[370] We might go on and give a dozen such instances of geological
miscalculations of time did space permit; but these are enough to
disabuse us of any faith in such calculations.

With such specimens before us of the miscalculations of the smaller
periods by geologists, we are not surprised to find that they grossly
exaggerate the larger cycles of time. The necessities of the evolution
of the ascidian into the snail, of the snail into the fish, and of the
fish into the lizard, of the lizard into the monkey, and of the monkey
into the man, by slow and imperceptible changes, demanded an almost
infinite length of time; and the geologists of that school accordingly
asserted the existence of animal life upon our globe for hundreds of
thousands of millions of years.

But Sir Wm. Thompson, one of the first mathematicians, demonstrates[371]
the impossibility of any such length of time being spent in the process
of cooling our little globe. Beginning with their own assumption, of a
globe of molten granite cooling down to the present state, he proves
that the earth can not have been in existence longer than a hundred
millions of years; and of course that plants and animals have existed on
it a much shorter time; as for the greater part of that period it was
too hot for them. The geologists are now becoming ashamed of their
poetical cycles, and some acknowledge that their chiefs blundered
egregiously in their calculations.

The principles of geology seem to be as unsettled as its fa