AMICI, GiovANNI BATTISTA, a celebrated designer and constructor of optical instruments, was born at Modena in 1784. While studying mathematics at Bologna, he acquired a taste for astronomical science, and devoted himself early in life to the improvement of astronomical instruments with great ingenuity and success. For the specula of his reflecting telescopes he prepared a very hard alloy, capable of receiving and retaining a fine polish, and to prevent spherical aberration he wrought the specula into an elliptical form. About 1812 he undertook the construction of a telescope with a five-foot speculum, and the gun-foundry at Pavia was put at his disposal for this purpose by the war minister of Italy, but the project was broken off, owing apparently to political complications. Amiei is still better known from his microscopes. His reflecting microscopes, with ellipsoidal specula, were an improvement on all that had preceded them, and he attained still greater success in the construction of compound achromatic object-glasses. His compound microscope was the first that could be used either in a vertical or in a horizontal position. His prism, too, for the oblique illumination of objects of microscopical observation is much commended. Amici was a very diligent and skilful observer ; and his intimate acquaintance with the principles of optical science enabled him to arrange his apparatus to the very best advantage. Various papers recording the results of his observations, which he read before learned societies, were published in scientific journals. They treat of the measurement of the diameters of the sun (by means of a micrometer he invented) and other astronomical subjects, the circulation of the sap in plants, the fructification of plants, infusoria, &c. After holding for some time a professorship of mathematics in Modena, he was in 1831 appointed inspector-general of studies in the duchy. A few years later he was entrusted with the charge of the observatory at Florence, where he also delivered lectures as professor of mathematics at the museum of natural history. He died in April 1863.