By the invention and assistance of magnifying glasses, the two extremes of the creation, as Mr. Baker intimates, which were out of the reach of former ages, have been brought under our observation: the telescope is directed to the heavenly bodies, and the microscope to unknown species of animals, &c. The first appearance of the microscope was about the year 1621; since which period it has been very much improved. It is to this valuable optical instrument that we are indebted for a great part of our present philosophy: we are brought into a kind of new world.
Numberless animals are discovered, which, from their minuteness, must otherwise for ever have escaped our observation. How many kinds of these invisibles there may be, says Mr. Adams, is still unknown; as they are discerned of all sizes, from those which are barely invisible to the naked eye, to such as resist the action of the microscope, as the fixed stars do that of the telescope, and with the greatest powers hitherto invented appear only as so many moving points.
The smallest living creatures our instruments can show, are those which inhabit the waters; for though animalcules, equally minute, may fly in the air, or creep upon the earth, it is scarcely possible to get a view of them; but as water is transparent, and confines the creatures in it, we are able, by applying a drop of it to our glasses, to discover, to a certain degree of smallness, all that it contains.
“Where the pool
Stands mantled o’er with green, invisible,
Amid the floating verdure millions stray.
Each liquid, too, whether it pierces, soothes,
Inflames, refreshes, or exalts the taste,
With various forms abounds. Nor is the stream
Of purest crystal, nor the livid air,