not very much less than that reflected by newly fallen snow. Such reflective power at once suggests an atmosphere very dense and heavily cloud-laden; and other observations point in the same direction. So that in the very first two planets of the system we are at once confronted with that diversity in details which coexists throughout with a broad general likeness as to figure, shape of orbit, and other matters. Mercury's reflective power is very small, that of Venus is exceedingly great; Mercury's atmosphere seems to be very attenuated, that of Venus, to all appearance, is much denser than that of our own earth. Periodically, when Venus appears in all her splendour in the Western sky, one meets with the suggestion that we are having a re-appearance of the Star of Bethlehem; and it seems to be a perpetual puzzle to some people to understand how the same body can be both the Morning and the Evening Star. Those who have paid even the smallest attention to the starry heavens are not, however, in the least likely to make any mistake about the sparkling silver radiance of Venus; and it would seem as though the smallest application of common-sense to the question of the apparent motion of a body travelling round an almost circular orbit which is viewed practically edgewise would solve for ever the question of the planet's alternate appearance on either side of the sun. Such an orbit must appear practically as a straight line, with the sun at its middle point, and along this line the planet will appear to travel like a bead on a wire, appearing now on one side of the sun, now on another. If the reader will draw for himself a diagram of a circle (sufficiently accurate in the circumstances), with the sun in the centre, and divide it into two halves by a line supposed to pass from his eye through the sun, he will see at once that when this circle is viewed edgewise, and so becomes a straight line, a planet travelling round it is bound to appear to move back and forward along one half of it, and then to repeat the same movement along the other half, passing the sun in the process.