In 1876 he visited America to attend the Centennial Exposition in Philadelphia. While crossing the ocean he noted the regularity of the trade winds, which led him to believe that balloon voyages might be made across the Atlantic. Some years later Andrée passed a winter in Spitzbergen, directing experiments and observations in atmospheric electricity. This scientific work strengthened his belief that a balloon might be navigated through the air in much the same manner as a ship through water. From this time Andrée studied the construction of balloons with great care, and in 1895 he astonished the world by making known his plan to reach the North Pole by means of an air route. He needed the sum of $36,000 in order to carry out his project. This amount was generously provided by King Oscar and two citizens of Sweden. Then Andrée set about the work of having a balloon constructed which would suit his purpose. He went to Paris, and secured the services of the most noted balloon maker in the world. This man built a balloon for Andrée which was ninety-seven feet high by sixty-seven feet in diameter. It was made of three thicknesses of silk, and varnished over twice, inside and out. It was handled by means of valves. The whole balloon was covered with a network of hemp, ending in forty-eight suspension ropes, to which the wooden bearing ring was attached. The car, shaped like a cylinder and made of wicker, was covered with tarpaulin, and was intended for rest and sleep. The place for work and observation was a swinging gallery, which also served for the roof of the car. In this gallery the scientific instruments were kept. Andrée took with him thermometers, barometers, cameras, and every sort of needful apparatus. The car contained a sleeping bag, and stores of books, maps, toilet articles, arms, and ammunition. The balloon was built to carry three passengers. While one slept, the other two expected to remain on the roof, taking observations and guiding the balloon. The bearing ring was the main storeroom. Crosspieces of wood formed a floor, upon which many necessary articles were packed. Boats, sledges, sails, ropes, and provisions of all kinds were stored away in forty-eight large sacks, which were hung to the bearing ring. Andrée had provisions enough to last for nine months, and everything was packed so as to occupy as little space as possible. Three sails and three guide ropes were arranged to aid in steering the balloon. The long guide ropes trailed behind the balloon, serving the purpose of a rudder. The sails caught the wind, increased the speed, and permitted change of direction.