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finally due east of Gettysburg, a few miles east of York, Penn. On this occasion I found the air warmer at the height of 15,000 feet than it was at the surface of the earth at the time of starting. 

You are right about the percolation of gas, or, as it is technically termed, exosmose of gas, but I propose to meet this in an equivalent expenditure of ballast of 6,000 pounds in weight, say from thirty to forty pounds per hour. That would keep us afloat six days. We are arriving at a better impermeability, and hope to reduce it to twenty pounds per hour, which would keep us afloat twelve days. Should we fail in this expectation of perfection in the air-float, and thus be brought down to the water level, we shall be prepared for that contingency in a seaworthy boat and an experienced sailor. Our great object is more to demonstrate a meteorological principle than the transit of the sea, desirable a feat us the latter may be. If we get but half way across we shall claim it as demonstrative of both the questions—feasibility of transmarine ballooning, and the proof that the air-tide is eastward continually, and thus establish another principle of weather signal service in which we can inform our neighbors on the other side of the ocean what kind of weather is coming over to them three to four days in advance of its coming. Your article is encouraging more than disparaging, and is calculated to keep alive to the necessity of keeping an eye toward the best possible construction of our machinery.

J. WISE.