328 PROF. EHRENBERG ON ANIMALS OF THE CHALK 
by the mere process that each single animalcule can divide itself, 
within one hour, completely lengthwise or across, and after the 
lapse of one hour’s rest can repeat the same thing. The vast 
effect of this activity, not perceptible in its detail, is, that a single 
animalcule, perfectly invisible to the naked eye, under circum- 
stances favourable for all individuals, which usually do not occur, 
can possibly be increased in four days to 140 billions of indepen- 
dent animalcules. Now in the polishing slate of Bilin,about 41,000 
millions form one cubic inch of stone, as may easily and pretty ac- 
curately be determined from the size and form of the corpuscles ; 
consequently about seventy billions to each cubic foot of the geo- 
enostical stratum actually occurring there. Accordingly, this pro- 
lific nature of the living animalcules, if it pertains in like man- 
ner to Gallionella distans, would cause the production in four 
days, from one of the latter, of 140 billions of siliceous shells ; 
or, which is the same thing, two cubic foot of a stone similar 
to the polishing slate or foliated tripoli of Bilin might be formed 
in four days from an imperceptible animal. We may here call to 
mind the exuberant but for the most part unproductive flower- 
ing of fruit-trees, and Buffon’s celebrated calculation of the 
possible but never-occurring production of wood from the seed 
of a single elm; yet these views of existing forces and arrange- 
ments in organic nature are by no means empty speculations to be 
compared with the idle calculations of the number of steps which 
a man takes in his lifetime, or the number of grains of sand 
which would fill the earth’s space; but they are records of 
actual relations of the living effect of hidden forces whose gra- 
dual tranquil progress astonishes man by its product, after the 
lapse of several of his generations, though perhaps unheeded in 
the lifetime of an individual; so that this simple natural effect, 
whenever, being favoured by collateral circumstances, it is more 
strikingly apparent than usual, may well seem marvellous or 
difficult of explanation ; while the attentive observer only recog- 
nises in its extraordinary extension the accustomed course of na- 
ture less than usually disturbed. Thus one might well stand sur- 
prised and amazed before mountain chains composed of imper- 
ceptible minute animalcules nearly of one and the same species ; 
but just as readily will a satisfactory explanation be found in” 
the above physiological observations of the possible productive-— 
ness of these same animalcules. Nor shall we be in haste to- 
conclude that for the formation of such astonishingly vast solid 
masses an immense period must have been requisite ; as the con 
