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HISTORICAL VIEW OF THE

and imagined the crystalline lens to be the part inwhich it is formed. In one passage he has been inter-preted as anticipating the discovery of the telescope,but an attentive examination clearly shows that hiswords will not fairly bear any such construction. Hementions the reflection of cold at the focus of a concavespeculum, which is estimated by using the eye in theplace of a thermometer. This very singular suggestionwould seem to imply a greater advance in speculationson the nature of heat than we can suppose to belong tothis age. It does not clearly appear whether this methodwas ever actually tried, or is a mere suggestion ; nor atthis day are we aware of any thing being known whichcan clear up the point.

Though much of the “ Magia Naturalis” is de-voted to experiments and contrivances of a frivolousnature, yet it exhibits a close acquaintance with scien-tific principles. The work became very popular, andwas translated into several languages. The generaldisposition of the age was now more favourable to thedissemination of knowledge, and the facilities affordedby the rapid multiplication of books, were beginning tobe productive of the best effects in enlightening thepublic mind. Porta also was personally popular, andhis house became the resort of the curious and learned ;but all this awakened the jealousy of the church ; andnot only the works of the Neapolitan philosopher, buteven his private parties became objects of suspicion tothe ecclesiastics. We do not, however, find that theyproceeded to any direct acts of persecution ; perhapstheir victim had the caution to give them no occasionfor doing so.

Dr. Gilbert, of Colchester, published a work onmagnetism in 1590, which contains a copious collec-tion of valuable facts and ingenious reasonings. Hemay be said to have laid the foundation of our know-ledge in this department of science, which has sinceopened into so many new and important analogies.

He extended his enquiries, also, into the kindred