Pliny the younger, in his letters, characterizes the work of his uncle truly "as a learned book, full of matter, not less manifold in its subjects than nature herself is." There are many things in Pliny which are generally objected to as unnecessary and foreign to his subject, but that most competent critic, Alexander Von Humboldt, is disposed to speak of the general result in terms of praise. "It appears to me to be particularly gratifying, that he so frequently, and always with so much pleasure, alludes to the influence exerted by nature upon the moral and intellectual development of man. His plan of connecting the subject is seldom well chosen. For example, the account of mineral and vegetable matter leads him to a fragment from the history of sculpture; a fragment which has been of almost more importance for the present condition of our knowledge than anything referring to descriptive natural history which can be extracted from the work." Pliny evidently had a feeling for art, but he seldom betrayed an artistic feeling in the forms of his scientific disquisition. His data came from books rather than from nature direct, and a sombre hue invested all he wrote. As Aristotle had garnered all anterior wealth in the same department, and passed it over to the Romans, so Pliny, in turn, gathered up later accumulations, and transmitted the grand aggregate to the middle ages. Providence always has the man ready for the needful task. That the ancients made some powerful applications of the lens is evident from the account given by Lucian and Galen, that Archimedes burned the Roman fleet at the siege of Syracuse, by means of glasses, B.C. 212. But neither the Greeks nor Romans have left us any account of the lens being applied to increase the stores of discovery in natural science. The only authentic records we have respecting the microscope, or its still more powerful correlative, belong to that age of scientific invention for the advent of which the Augustan age was appointed to prepare.