The history of the modern microscope, like that of nations and arts, has had its brilliant periods, in which it shone with uncommon splendour, and was cultivated with extraordinary ardour; these periods have been succeeded by intervals marked with no discovery, and in which the science seemed to fade away, or at least to lie dormant, till some favourable circumstance--the discovery of a new object, or some new improvement in the instruments of observation--awakened the attention of the curious, and reanimated the spirit of research. Thus, soon after the invention of the microscope, the field it presented to observation was cultivated by men of the first rank in science, and who enriched almost every branch of natural history by the discoveries made by means of this instrument. The Modern Microscope. To the celebrated Dr. Hooke belongs the honour of publishing an account of the compound instrument in 1665 in his “Micrographia.” His first claim, however, is founded on the application of a lamp adjustable on a pillar, together with a glass globe of water and a deep plano-convex condensing lens. By means of this arrangement, he says, “The light can be directed more directly on the object under examination.” In the further description given of his microscope, he explains: “It has four draw-tubes for lengthening the body, and a third lens to the optical combination.” This, it would appear, was only brought into use when he wished to see the whole object at once: “The middle-glass lens, conveying a very great company of radiating pencils (of light) which would stray away; but when I had occasion to examine the small parts of a body, I took out the middle glass and made use of one eye-glass with the object-glass.”