wherein the Tinging matters are boyl'd, and so great an Influence may an unheeded Circumstance have on the Success of Experiments concerning Colours. * * * * * _FINIS._ * * * * * A SHORT ACCOUNT OF SOME OBSERVATIONS Made by Mr. _BOYLE_ About a _Diamond_ that _Shines_ in the Dark. First enclosed in a Letter written to a Friend, And now together with it annexed to the Foregoing Treatise, upon the score of the Affinity Betwixt _Light_ and _Colours_. * * * * * _LONDON,_ Printed for _Henry Herringman_. 1664 * * * * * A COPY OF THE LETTER That Mr. _Boyle_ wrote to Sir _Robert Morray_, to accompany the _Observations_ touching the _Shining Diamond_. _SIR,_ Though Sir _Robert Morray_ and Monsieur _Zulichem_ be Persons that have deserv'd so well of the Commonwealth of Learning, that I should think my self unworthy to be look'd upon as a Member of it, if I declin'd to Obey them, or to Serve them; yet I should not without Reluctancy send you the Notes, you desire for him, if I did not hope that you will transmit together with them, some Account why they are not less unworthy of his perusal; which, that you may do; I must inform you, how the writing of them was Occasion'd, which in short was thus. As I was just going out of Town, hearing that an Ingenious Gentleman of my Acquaintance, lately return'd from _Italy_, had a Diamond, that being rubb'd, would shine in the Dark, and that he was not far off, I snatch'd time from my Occasions to make him a Visit, but finding him ready to go abroad, and having in vain try'd to make the Stone yield any Light in the Day time, I borrow'd it of him for that Night, upon condition to restore it him within a Day or two at furthest, at _Gresham_ College, where we appointed to attend the meeting of the Society, that was then to be at that place. And hereupon I hasted that Evening out of Town, and finding after Supper that the Stone which in the Day time would afford no discernable Light, was really Conspicuous in the Dark, I was so taken with the Novelty, and so desirous to make some use of an opportunity that was like to last so little a while, that though at that time I had no body to assist me but a Foot-Boy, yet sitting up late, I made a shift that Night to try a pretty number of such of the things that then came into my thoughts, as were not in that place and time unpracticable. And the next Day being otherwise imploy'd, I was fain to make use of a drowsie part of the Night to set down hastily in Writing what I had observ'd, and without having the time in the Morning, to stay the