In order to compare the Light of the Sun with that of a Star, Dr. Wollaston took as an intermediate object of comparison the light of a candle reflected from a bulb about a quarter of an inch in diameter, filled with quicksilver; and seen by one eye through a lens of two inches focus, at the same time that the star on the sun’s image, _placed at a proper distance_, was viewed by the other eye through a telescope. The mean of various trials seemed to show that the light of Sirius is equal to that of the sun seen in a glass bulb 1/10th of an inch in diameter, at the distance of 210 feet; or that they are in the proportion of one to ten thousand millions: but as nearly one half of this light is lost by reflection, the real proportion between the light from Sirius and the sun is not greater than that of one to twenty thousand millions. “THE SUN DARKENED.” Humboldt selects the following example from historical records as to the occurrence of a sudden decrease in the light of the Sun: A.D. 33, the year of the Crucifixion. “Now from the sixth hour there was darkness over all the land till the ninth hour” (_St. Matthew_ xxvii. 45). According to _St. Luke_ (xxiii. 45), “the sun was darkened.” In order to explain and corroborate these narrations, Eusebius brings forward an eclipse of the sun in the 202d Olympiad, which had been noticed by the chronicler Phlegon of Tralles (_Ideler_, _Handbuch der Mathem. Chronologie_, Bd. ii. p. 417). Wurn, however, has shown that the eclipse which occurred during this Olympiad, and was visible over the whole of Asia Minor, must have happened as early as the 24th of November 29 A.D. The day of the Crucifixion corresponded with the Jewish Passover (_Ideler_, Bd. i. pp. 515-520), on the 14th of the month Nisan, and the Passover was always celebrated at the time of the _full moon_. The sun cannot therefore have been darkened for three hours by the moon. The Jesuit Scheiner thinks the decrease in the light might be ascribed to the occurrence of large sun-spots. THE SUN AND TERRESTRIAL MAGNETISM. The important influence exerted by the Sun’s body, as a mass, upon Terrestrial Magnetism, is confirmed by Sabine in the ingenious observation, that the period at which the intensity of the magnetic force is greatest, and the direction of the needle most near to the vertical line, falls in both hemispheres between the months of October and February; that is to say, precisely at the time when the earth is nearest to the sun, and moves in its orbit with the greatest velocity. IS THE HEAT OF THE SUN DECREASING?