Observations made at the observatory of the British Association, detected, in 1850, sudden brightenings of the light, altogether different from pulsations. The theory would refer these to that fitful irregularity in the momentary intensity of the radial stream, which gives the flickering and tremulous motion to comets' tails. But, the steady variations in the intensity of this light must be due to other causes. The longitude of the sun will here come in as a modifying cause; for the obstruction caused by the body of the sun, when displaced from the axis of the vortex, must necessarily exercise an influence on the force and direction of the radial stream. A sudden influx of cometary matter down the poles of the vortex, in more than usual quantities, will also tend to brighten and enlarge the zodial light; and, in this last cause, we have an explanation not only of ancient obscurations of the solar light, but, also, of those phosphorescent mists, such as occurred in 1743 and 1831, rendering moonless nights so light that the smallest print could be read at midnight. In total eclipses of the sun, the denser portion of the zodial light is visible as a brilliant corona; but, on such occasions, the brightest stars only are to be seen, and, consequently, the fainter portions of the light must be invisible. Hind mentions as many as ten stars visible in the total eclipse of 1842. According to the same authority, the color of the corona was like tarnished silver, and rays of light diverged in every direction, and appeared shining through the light of the corona in the total eclipse of 1851. In this year on the day of the eclipse (July 28th), the longitude of the sun was about 340°, and, therefore, the body of the sun obstructed the radial stream as seen from the earth on the right side; but, in 1842, the longitude of the sun was, according to our table, about 116°, the sun's centre then being 700,000 miles from the axis of the vortex, and on the opposite side with respect to the earth; the position was, therefore, not so favorable for the appearance of these rays which, in many cases, have given the appearance of a whirling motion to the corona.