choicest productions of nature gratify the appetite and please the eye. In the greatest heats of summer, coolness, shade, and moisture are found in the green forest glades; and we can thus understand how our visual apparatus has become especially adapted to receive pleasurable and soothing sensations from this class of rays. _Supposed increase of Colour-perception within the Historical Period._--Some writers believe that our power of distinguishing colours has increased even in historical times. The subject has attracted the attention of German philologists, and I have been furnished by a friend with some notes from a work of the late Lazarus Geiger, entitled, _Zur Entwickelungsgeschichte der Menschheit_ (Stuttgart, 1871). According to this writer it appears that the _colour_ of grass and foliage is never alluded to as a beauty in the Vedas or the Zendavesta, though these productions are continually extolled for other properties. Blue is described by terms denoting sometimes green, sometimes black, showing that it was hardly recognised as a distinct colour. The _colour_ of the sky is never mentioned in the Bible, the Vedas, the Homeric poems, or even in the Koran. The first distinct allusion to it known to Geiger is in an Arabic work of the ninth century. “Hyacinthine locks” are black locks, and Homer calls iron “violet-coloured.” Yellow was often confounded with green; but, along with red, it was one of the earliest colours to receive a distinct name. Aristotle names three colours in the rainbow--red, yellow, and green. Two centuries earlier Xenophanes had described the rainbow as purple, reddish, and yellow. The Pythagoreans admitted four primary colours--white, black, red, and yellow; the Chinese the same, with the addition of green.