The hydrogen produced by this reaction passes into a purifier “L,” filled with coke, and provided with a tapering grate; through this grate the gas makes its way into the washing compartment, and passes through the column of coke in which is circulating the water that falls from the rose attached to the top. [Illustration: SKETCH OF THE CONSTRUCTION OF THE HYDROGEN GAS-PRODUCING APPARATUS.] The overflow runs away through a pipe at “U” at the bottom of the apparatus. A steam-pump feeds the purifier and the mixing tank with sea-water, which, by the way, is quite suitable for this process. On leaving the purifier the hydrogen traverses a chamber “H,” from which two tubes lead to the dryers “S”; these dryers consist of rectangular boxes containing purifying materials and quicklime laid on a grating near the bottom. Before being conveyed into the balloon the gas thus prepared passes through two testing chambers “E,” each of which contains a thermometer, a hygrometer, and some litmus-paper; glass sight-holes are provided to facilitate inspection. Pressure gauges fixed in various positions show the pressure of the gas current. This voluminous apparatus is capable of producing 5,297 to 7,000 cubic feet of gas per hour, but Andrée will not allow the output to exceed 2,118 cubic feet per hour, his object being to secure a gas which has had ample time for proper washing and purifying. _June 20th._—During the first twenty-four hours about 42,379 cubic feet of gas were generated. Andrée and Fraenkel are busy to-day superintending the inflation of the balloon; the rest are preparing for a trip northwards with the steam-barge commanded by Lieutenant Norselius. [Illustration: GETTING THE BALLOON CASE ASHORE.] They propose reaching Red Bay, to the N.E. of Spitzbergen, near 80° parallel. We left Virgo Bay at nine in the morning, and steered to the north along the coast of Smeerenburg. As we went along the guns brought down several birds. At one o’clock we were at Red Bay, which was one immense ice plain reaching up to the islands at the entrance to the bay. It was on one of these islands, not shown in any polar chart, that we landed and scared away a flock of eiders and a fox which was lying in ambush for them. From our position we commanded a full view of the entire expanse of the gulf. Here nature presents a wilder aspect than we have ever seen her under. The bay opens out towards the north. East and west the bay is flanked with lofty mountains whose summits are lost in the fog; wide fissures afford shelter to enormous numbers of birds of various species, who build their nests at different altitudes. Some perch on the sharp edges of the rock, while others describe huge curves or shoot along after the manner of birds of prey. We noticed some wild geese, some goelands, the “king of the algæ,” the auk, and others, all filling the air with sharp piercing cries, deafening one with their fiendish concert.