The largest balloon in the world, according to the San Francisco Chronicle, has recently been built in that city by Mr. A. P. Van Tassel. It has a capacity of 150,000 cubic feet of gas, and has been constructed for the special purpose of enabling the well known aeronaut to undertake a journey across the continent, from ocean to ocean. The height from the floor of the wicker car to the top of the gas reservoir is 119 feet, and of the dilated reservoir alone 68 feet. The envelope is made of finely woven cloth, manufactured expressly for the purpose, and is varnished, as usual, in order to make it gas tight. The car has accommodation for fifteen persons. It is about twenty-one feet in circumference, and the sides are thirty-four inches high. The supporting ropes are kept in place by the usual “ concentrics.” Hydrogen gas will be used for inflating the balloon. The cost, of the structure (is stated to be $6,000. Mr. Van Tassel has had consider able experience in aerial traveling, having crossed the Wichita Mountains, 15,000 feet above sea level. His present attempt is more ambitious than any he has yet made. i. careful study of the aerial currents leads him to believe that by seeking the proper stratum of air he can be carried eastward at high speed, possibly 100 miles an hour. The greatest difficulty will probably be due to the Rocky Mountains, which modify the movements of the air currents over a large area of the continent. It is expected that the voyage will be begun some time about the 1st of July. Should it survive the trip, the giant balloon will be taken back to San Francisco, where it will be placed on exhibition.