S 6o H E L M I N T 
the-mod furprifing circumftance to the natural philofo- 
pher is the rapidity with which this material is formed, 
and the magnitude with which it is prefented, in the for¬ 
mation of coral rocks; which rife fpoptaneoufly out of 
the fea, and become by length of time fuffic'iently capa¬ 
cious to be inhabited by man. Such are the Friendly 
I (lands, and feveral others in the Indian Ocean ; for the 
intereding particulars of which we beg to refer the curi- - 
ous reader to the article Coral, vol. v. p. i 3 S. 
INFUSORIA, or WORMS generated in INFU¬ 
SIONS. 
The individuals of this order are commonly denomi¬ 
nated animalcules, becaufe they are in general ft) extreme¬ 
ly minute, as not to be cognizable to the naked eye ; 
but have been chiefly made known to us by the powers 
of the microfcape. By means of this noble indrument 
we are as it were introduced'into a new world; and 
made acquainted with an order of beings which, from 
their extraordinary minutenefs, mud otherwife have for 
everefcaped our knowledge and obfervation. And how- 
many kinds of thefe invifibles there may be, is quite 
unknown; for they are obferved ofall fizes, from thofe 
which are barely invifible, to fuch as redd even the ac¬ 
tion of the microfcope, and under the dronged magni¬ 
fier hitherto invented appear only as moving points. 
The dualled living creatures thefe indruments can Ihow, 
are thofe which inhabit the waters; for, though ani¬ 
malcules equally minute, or perhaps more fo, may in¬ 
habit the atmofphere, or creep upon the earth, yet it is 
fcarc.ely poflible to obtain a view of them; whereas, 
water being tranfparent, and confining the creatures 
within it, we are enabled, by applying a drop of it to 
the lens, to difcover with eafe a great part of its con¬ 
tents, and in a fpace barely vifible to the naked eye 
often perceive a thoufand little animals full of life and 
vigour. 
But in the examination and profecution of this curious 
and delicate refearch, how many requifites are neceifary, 
,and what a variety of favourable circumdances mud be 
ieized, fo as to enable us to conduct it with fuccefs! — 
A habit of obfervation acquired by long practice, fuit- 
able leifure, rigorous attention, perfevering mental ex¬ 
ertion, and, above all, inexhaudible patience!—We 
mud be able to manage the microfcope with more than 
common adroitnefs and care, fo as not to crufli the lit¬ 
tle creatures we wifli to become acquainted with, and 
which will often, in fpite of all our vigilance, feclude 
themfelves from our view. Still, to judge of their ha¬ 
bits and economy, to afcertain their figure, and demon- 
drate their genera and lpecies in the lcale of animated 
nature, we mud examine them in many different ways, 
in various filuations, and at different intervals-ef motion 
and red; at the fame time we mud be corredf defigners, 
and able to trace with fidelity and exattnefs, whatever 
the powers of the magnifier may prefent, as their ge¬ 
nuine features and organization. 
The animalcula infuforia take their name from their 
being found in all kinds either of vegetable or animal 
infufipns ; if feeds, herbs, or other vegetable fubdances, 
be infufed in water, it will foon be filled with an inde¬ 
finite number of thefe minute creatures. There is a 
prodigious variety in their forms ; fome appear bell- 
fhaped ; others round or oblong, without any apparent 
members ; fome referable a bulb with a long taper tail; 
others are nearly fpherical; the greater part are vefi- 
cular and tranfparent. Thofe mod generally found in 
ditch-water are like inflated bladders, with a fmall trace 
of intedines in the centre ; the next are a flat kind, with 
a number of legs under their belly. In all of them 
motion feems to be their chief delight; they pervade 
with equal eafe and rapidity, and in all forms and direc¬ 
tions, the dimenfions of a fingle drop of water, in which 
they find ample fpace for their various progreffions, 
fometim.es darting draight forward, at other times mov- 
H O L O G Y. 
ing obliquely, then again circularly: they know how to 
avoid with dexterity any o'bdacles that might obdrutt 
their progrefs. 
Among animalcules, as in every other part of nature, 
there is condantly a certain proportion preferved between 
the fize of the individuals and their number. There are 
always fewed amongd the larger kinds, but they increafe 
in number as they diminifli in fize, till of the lad, or 
lowed to which our powers of magnifying will read), 
there are myriads to one of the larger. Like other ani¬ 
mals, they increafe in fize from their birth till they have 
attained their full growth. When deprived .of food, 
they grow thin and perifli; and different degrees of or¬ 
ganization are to be difcovered in their drutture. The 
birth and propagation of thefe microfcopic animalcules 
is alfo as regular as that of the larged animals of out- 
globe ; for though their extreme minutenefs prevents 
us, in mod cafes, from feeing the germ from which they 
fpring, yet we are well affined, from numerous obfer- 
vations, that die manner in which they multiply is re¬ 
gulated by Conflant and invariable laws. 
It is unquedionably an objeft of the highed admira¬ 
tion to have invented means for bringing creatures fo 
imperceptible as thefe animalcules under our cognizance 
and infpebtion. One might well have deemed an obje£t 
that was a thoufand times too minute to aftebt our vi- 
fion, as perfectly removed from human difcovery; yet 
we have extended our fight over animals to whom thefe 
would be mountains. The naked eye takes in animal 
beings from the elephant to the mite; but below this, 
commences a new order, referved only for the microfcope, 
which comprehends all thofe from the mite, to thofe 
many millions of times fmaller; and this order cannot 
be faid to be exhaufted, if the microfcope be not arrived 
at its ultimate date of perfedlion. In fadt, the greater 
number of microfcopic animalcules are of fo fmall a 
fize, that through a lens, whofe focal didance is the 
tenth part of an inch, they only appear as fo many 
points; that is, their parts cannot be didinguilhed, fo 
that they appear from.the vertex of that lens under an 
angle not exceeding the minute of a degree. If we in- 
vedigate the magnitude of fuch an objedl, it will be 
found nearly equal to of an inch long. Suppo- 
fing, therefore, thefe animalcules to be of a cubic figure, 
that is, of the fame length, breadth, and thicknefs, their 
magnitude would be expreffed by the cube of the frac¬ 
tion 75^, that is, by the number T oooOooOci o oooff g'ff> 
that is, each animalcule is equal to to many parts of 
a fquare inch. This contemplation of the animalcules 
has rendered the idea of indefinitely fmall bodies very 
familiar to us; a mite was formerly thought the limit 
of littlenefs, but we are not now furprized to be told 
of animals many millions of times fmaller than a mite. 
Thefe confiderations are dill further heightened, by re- 
fledling on the internal drudlure of animalcules; for each 
mud have all the proportion, fymmetry, and adjuft- 
ment, of that organized texture which is indifpenfably 
neceflary for the feveral functions of life ; and each mud 
be furnilhed with proper organs, tubes, &c. for fecret- 
ing the fluids, digeding its food, and propagating its 
fpecies. 
Minute animals proportionably exceed the larger kinds 
in drength, activity, and vivacity. It is well known 
that the fpring of a flea vadly outdrips any thing ani¬ 
mals of a greater magnitude are capable of; the motion 
of a mite is much quicker than that of the fwifted race- 
horfe. M. De LTfle, Hid. Acad. Scienc. 1711, p. 23, 
has given the computation of the velocity of a little 
creature, fo fmall as to be fcarcely vifible, which he 
found to run three inches in a fecond ; fuppofing now 
its feet to be the fifteenth part of a line, it mud make 
five hundred deps in the fpace of three inches, that is, 
it mud Ihift its legs, five hundred times in a fecond, or 
in the time of the ordinary pulfation of an artery . The 
rapidity with which many of the water infedis Ikim the 
r fttrface 
