The horns, or angles of the moon will, of course, appear distinct and sharp or indistinct and blunt, in proportion to the amount of condensation in the atmosphere which impedes the passage of the light. For the same reason, when the moon is new, her entire disk is visible when the atmosphere is very clear, by reason, as is supposed, of light reflected from the earth to the moon and back to us. This double reflection can only take place when the atmosphere is very clear. Hence, Virgil alludes to it, and correctly, as an indication of continued fair weather: "If (mark the ominous hour!) The clear fourth night her lucid disk define, That day, and all that thence successive spring, E'en to the finished month, are calm and dry." Probably Virgil alluded to a month of the summer trade-wind drouth which reaches up on Southern Italy. But that appearance of the moon is occasionally seen here, and the indication is, in degree, philosophically true. It is somewhat more difficult to determine what will be the result of the condensation seen at the west in the morning, and which is not so far east, or of such a character, as to reflect the rays of the sun; for, although always suspicious, it is sometimes of a foggy character, and disappears between eight and nine o'clock. If it increases in density after ten o'clock, or is of a dense cirro-stratus character, rain may generally be expected. If of a decided _cirro-cumulus_ character, it is certain to disappear. Cirro-cumulus is seen in small patches, with small, distinct, and rounded masses, in summer, in the morning, and sometime, during the day, after high fog has disappeared, and at other times, and is always, when of that _distinct_ character, a fair weather indication. I have seen it thus when the wind was blowing from the N. E., and the scud running toward a storm passing near, but to the south of us, when those who relied upon the existence of the wind and scud as evidences that we were to have the desired rain, were deceived. Thus, the couplet from an old almanac: "If _woolly fleeces_ strew the heavenly way, Be sure no rain disturb the summer day." When this morning condensation is not high fog, and is dense and passing east with a wavy appearance, it is very certain to rain. Jenner says: "The boding shepherd heaves a sigh, _For see, a rainbow spans the sky_." An old almanac had the following verse: "A rainbow in the morning Is the shepherd's warning; A rainbow at night Is the shepherd's delight." So the proverb was originally made; but as our ancestors were not shepherds, and had a horror of ocean storms, it was commonly quoted, in this country, in the following form: "A rainbow in the morning, The sailors take warning," etc.