The first thing, then, was to locate the Lake of the Sun on the smoke-hidden surface of the planet beneath us. This was a problem that the astronomers could readily solve. Fortunately, in the flagship itself there was one of the star-gazing gentlemen who had made a specialty of the study of Mars. That planet, as I have already explained, was now in opposition to the earth. The astronomer had records in his pocket which enabled him, by a brief calculation, to say just when the Lake of the Sun would be on the meridian of Mars as seen from the earth. Our chronometers still kept terrestrial time; we knew the exact number of days and hours that had elapsed since we had departed, and so it was possible by placing ourselves in a line between the earth and Mars to be practically in the situation of an astronomer in his observatory at home. Then it was only necessary to wait for the hour when the Lake of the Sun would be upon the meridian of Mars in order to be certain what the true direction of the latter from the flagship was. Having thus located the heart of our foe behind its shield of darkness, we prepared to strike. The Smoke Must Be Shattered. "I have ascertained," said Mr. Edison, "the vibration period of the smoke, so that it will be easy for us to shatter it into invisible atoms. You will see that every stroke of the disintegrators will open a hole through the black curtain. If their field of destruction could be made wide enough, we might in that manner clear away the entire covering of smoke, but all that we shall really be able to do will be to puncture it with holes, which will, perhaps, enable us to catch glimpses of the surface beneath. In that manner we may be able more effectually to concentrate our fire upon the most vulnerable points." The Blow--And Its Effect. Everything being prepared, and the entire squadron having assembled to watch the effect of the opening blow and be ready to follow it up, Mr. Edison himself poised one of the new disintegrators, which was too large to be carried in the hand, and, following the direction indicated by the calculations of the astronomers, launched the vibratory discharge into the ocean of blackness beneath. A Terrible Encounter. The Martians and Our Warriors Fight a Battle to the Death. Instantly there opened beneath us a huge well-shaped hole, from which the black clouds rolled violently back in every direction. Through this opening we saw the gleam of brilliant lights beneath. We had made a hit. "It is the Lake of the Sun!" shouted the astronomer who furnished the calculation by means of which its position had been discovered. And, indeed, it was the Lake of the Sun. While the opening in the clouds made by the discharge was not wide, yet it sufficed to give us a view of a portion of the curving shore of the lake, which was ablaze with electric lights.