Following independent paths, he worked out some of Gilbert's discoveries in magnetism, and of Da Porta's in optics, demonstrated the valves of the veins, and the function of the uvea in vision, divined the uses of the telescope and thermometer.

When he turned his attention to astronomy, he at once declared the futility of judicial astrology; and while recognizing the validity of Galileo's system, predicted that this truth would involve its promulgator in serious difficulties with the Roman Inquisition.

In his treatises on psychology and metaphysics, he originated a theory of sensationalism akin to that of Locke.

There was, in fact, no field of knowledge which he had not traversed with the energy of a discoverer.
Only to poetry and _belles lettres_ he paid but little heed, disdaining the puerilities of rhetoric then in vogue, and using language as the simplest vehicle of thought.

In conversation he was reticent, speaking little, but always to the purpose, and rather choosing to stimulate his collocutors than to make display of eloquence or erudition.