Portrait by Boonen

Can any of your correspondents state the precise time when Boonen, said to be a pupil of Schalcken, flourished? And what eminent geographer, Dutch or English, lived during such period? This question is asked with reference to a picture by Boonen,—a portrait of a singular visaged man, with his hand on a globe, now at Mr. Peel's in Golden Square; the subject of which is desired to be ascertained. It may be the portrait of an astrologer, if the globe is celestial.