Miscellanea Curiosa.

Optick-glasses of other Figures than Spherical,) I procur'd me a Triangular Glass-Prism, to try therewith the celebrated Phænomena of Colours. And in order thereto, having darken'd my Chamber, and made a small hole in my Window-shuts, to let in a convenient quantity of the Sun's Light, I plac'd my Prism at his entrance, that it might be thereby refracted to the opposite Wall. It was at first a very pleasing Divertisement, to view the vivid and intense Colours produced thereby; but after a while applying my self to consider them more circumspectly, I became surpriz'd to see them in an oblong Form; which, according to the received Laws of Rarefraction, I expected