on what he calls Ocular Spectra, in the Philosophical Transactions, Vol.
LXXVI. which might much facilitate the execution of it. In this treatise
the Doctor has demonstrated, that we see certain colours, not only with
greater ease and distinctness, but with relief and pleasure, after having
for some time contemplated other certain colours; as green after red, or
red after green; orange after blue, or blue after orange; yellow after
violet, or violet after yellow. This he shews arises from the _ocular
spectrum_ of the colour last viewed coinciding with the _irritation_ of
the colour now under contemplation. Now as the pleasure we receive
from the sensation of melodious notes, independent of the previous
associations of agreeable ideas with them, must arise from our hearing
some proportions of sounds after others more easily, distinctly, or
agreeably; and as there is a coincidence between the proportions of the
primary colours, and the primary sounds, if they may be so called; he
argues, that the same laws must govern the sensations of both. In this
circumstance, therefore, consists the sisterhood of Music and Painting;
and hence they claim a right to borrow metaphors from each other;
musicians to speak of the brilliancy of sounds, and the light and shade
of a concerto; and painters of the harmony of colours, and the tone of a
picture. Thus it was not quite so absurd, as was imagined, when the blind
man asked if the colour scarlet was like the sound of a trumpet. As the
coincidence or opposition of these _ocular spectra_, (or colours which
remain in the eye after having for some time contemplated a luminous
object) are more easily and more accurately ascertained, now their laws
have been investigated by Dr. Darwin, than the _relicts_ of evanescent
sounds upon the ear; it is to be wished that some ingenious musician
would further cultivate this curious field of science: for if visible
music can be agreeably produced, it would be more easy to add sentiment
to it by the representations of groves and Cupids, and sleeping nymphs
amid the changing colours, than is commonly done by the words of audible
music.

_B._ You mentioned the greater length of the verses of Homer and Virgil.
Had not these poets great advantage in the superiority of their languages
compared to our own?

_P_. It is probable, that the introduction of philosophy into a country
must gradually affect the language of it; as philosophy converses in more
appropri