EXPERIMENTAL INQUIRY INTO THE CAUSE of the CHANGES of COLOURS I N OPAKE AND COLOURED BODIES. WITH AN HISTORICAL PREFACE Relative to the Parts of Philofophy therein examined, and to the ΠΡΟΣΕΞΕΥΡΕΙΝ, ΚΑΙ ΠΑΡΑΔΟΥΝΑΙ ΤΟΙΣ ΤΕ ΤΑΣ ΤΕΧΝΑΣ ΕΡΓΑΖΟ- Printed for J. NOURSE, Bookfeller to his Majefty; and P. ELMSLY, Entered at Stationers' Hall. M.DCC.LXXVII, IT T appears to be extremely worth the Time and Pains of Philofophers to inquire into the Orders of the Colours of natural Bodies, in the Manner proposed and begun by Sir Ifaac Newton; and particulary to compare the Changes of Colour, which turn up in chemical Operations, with the other Changes, which happen to the Subjects of the Operations, at the fame time. Nothing feems more likely than this to be a Key to the Philofophy of the fmall Parts of natural Bodies, and of their mutual Influences. Hartley's Obferva. C. 2. Sect. 4. Prop. 60. 11-7-35. M PREFACE. HE Subject of the following Work was fuggested to the Author, by a close attention to thofe Experiments of Sir Ifaac Newton, which fhew that Colours are exhibited by very thin plates of pellucid Media: and it is intended, as a kind of Supplement, to commence at that state of the Inquiry, in which it was left by that great Philofopher. The Substances which he employed in making his optical Experiments, were transparent and colourless: fuch as Glass, Water, and Air. And having diminished, or increased, the thickness of those substances by mechanical means, he produced, according to the different magnitudes of the pellucid Media, Differences or Changes of Colour. The Colours, however, exhibited in those Experiments, from their tranfient and temporary nature, were, I perceived, incapable of being applied to practical a 388266 |