Page:Optics.djvu/172

 In this Table the values relating to air were alone immediately obtained by observation; the others were calculated from them by means of the several ratios of refraction, that is, by multiplying them by for the vacuum,  for water, and  for glass. It must be remembered, that these values all suppose the incidence to be perpendicular.

Applying to these results a rule that he had found to determine the nature of the compound colour resulting from any given mixture of simple colours, Newton deduced the following Table, which shows the thickness at which the brightest tints of each ring appear, when seen under the perpendicular incidence. This table is calculated only for air, water, and common glass, but may of course be extended to all other substances, by the method above-mentioned.

The unit is the thousandth part of an inch. By the side of different colours are put the names of certain flowers or metallic substances, just to give more distinct ideas of them.