This valuable instrument, though not entirely unknown to the ancients, was re-invented and made public in the early part of the 17th century: it has, since that period, received continual improvements from various ingenious philosophers and artists, among whom the names of Leeuwenhoek, Wilson, Hook, the Adams's, Lie-berkuhn, Barker, Grey, Martin, Di Torre, and Dr. Smith, deserve to be gratefully recorded.
Microscopes are of two sorts, single and double. The former consist in general of one lens or mirror ; but, if a greater number be employed, they only serve to throw additional light upon the object, without farther enlarging its image. Double or compound mi-croscopes are those in which the image of an object is composed of several lenses or mirrors.
The utility of microscopes is very extensive, both to the naturalist and the artist: hence the invention of them must be regarded as one of the greatest efforts of human ingenuity. It is true, they do not contribute in any essential manner to the happiness of mankind ; but they serve to unfold the wonders of Nature, and thus insensibly raise the mind to the contemplation of that Great Being, whose works, however minute and apparently insignificant, uniformly evince the highest skill and most perfect symmetry.