When the ancients first observed Sirius emerging as it were from the sun, so as to become visible to the naked eye, they usually sacrificed a Brown Dog to appease its rage, considering that this Star was the cause of the hot sultry weather usually experienced at its appearance; and they would seem to have believed its power of heat, conjoined with that of the sun, to have been so excessive, that on the morning of its first rising the Sea boiled, the Wine turned sour, Dogs grew mad, and all other creatures became languid ; causing to man, among other diseases, burning fevers, hysterics, and phrensies.
That the weather in July and August is generally more sultry than at any other period of the year, and that some particular diseases are
consequently at that time more to be dreaded, both to man and beast, is past dispute. The exaggerated effects of the rising of Sirius are now, however, known to be groundless; and the superior heat usually felt during the dog-days, has been more philosophically accounted for. The sun at this period of the year, not only darts his rays almost perpendicularly upon us, and of course with greater power; but has also continued to exert his influence through the spring and summer seasons, whereby the atmosphere and earth have received a warmth, proportioned to the continuity of its action; and moisture, in itself naturally cold, has been dissipated:–Clavis Calendaria: or, A Compendious Analysis Of the Calendar Volume 2–John Henry Brady