Experiments and considerations touching colours first occasionally written, among some other essays to a friend, and now suffer'd to come abroad as the beginning of an experimental history of colours / by the Honourable Robert Boyle ...

EXPERIMENT III.

Whilst we were making the newly men∣tion'd Experiments, we thought fit to try also what Composition of Colours might be made by Altering the Light in its Pas∣sage to the Eye by the Interposition not of Perfectly Diaphanous Bodies, (that having been already try'd by others as well as by us (as we shall soon have occasion to take notice) but of Semi-opacous Bodyes, and those such as look'd upon in an ordinary Light, and not held betwixt it and the Eye, are not wont to be Discriminated from the rest of Opacous Bodyes; of this Tryal, our mention'd Adversaria present us the fol∣lowing Account.

Holding these Sheets, sometimes one sometimes the other of them, before the Hole betwixt the Sun and the Eye, with

the Colour'd sides obverted to the Sun; we found them single to be somewhat Trans∣parent, and appear of the same Colour as before, onely a little alter'd by the great Light they were plac'd in; but laying two of them one over another and applying them so to the Hole, the Colours were com∣pounded as follows.

The Blew and Yellow scarce exhibited any thing but a Darker Yellow, which we ascrib'd to the Coarseness of the Blew Pa∣pers, and its Darkness in its Kind. For ap∣plying the Blew parts of the Marbl'd Paper with the Yellow Paper after the same man∣ner, they exhibited a good Green.

They Yellow and Red look'd upon toge∣ther gave us but a Dark Red, somewhat (and but a little,) inclining to an Orange Colour.

The Purple and Red look'd on together appear'd more Scarlet.

The Purple and Yellow made an Orange.

The Green and Red made a Dark O∣range Tawny.

The Green and Purple made the Purple appear more Dirty.

The Blew and Purple made the Purple more Lovely, and far more Deep.

The Red parts of the Marbl'd Paper look'd upon with the Yellow appear'd of a

Red far more like Scarlet than without it.

But the Fineness or Coarseness of the Papers, their being carefully or slightly Colour'd, and divers other Circumstances, may so vary the Events of such Experi∣ments as these, that if, Pyrophilus, you would Build much on them, you must care∣fully Repeat them.