And it was at this period that the expedient of the ballon sonde, or unmanned balloon, was happily thought of. One of these balloons, the "Cirrus," among several trials, rose to a height, self-registered, of 61,000 feet, while a possible greater height has been accorded to it. On one occasion, ascending from Berlin, it fell in Western Russia, on another in Bosnia. Then, in 1896, at the Meteorological Conference at Paris, with Mascart as President, Gustave Hermite, with characteristic ardour, introduced a scheme of national ascents with balloons manned and unmanned, and this scheme was soon put in effect under a commission of famous names--Andree, Assmann, Berson, Besancon, Cailletet, Erk, de Fonvielle, Hergesell, Hermite, Jaubert, Pomotzew (of St. Petersburg), and Rotch (of Boston, Mass.).

In November, 1896, five manned balloons and three unmanned ascended simultaneously from France, Germany, and Russia. The next year saw, with the enterprise of these nations, the co-operation of Austria and Belgium. Messrs. Hermite and Besancon, both French aeronauts, were the first to make practical trial of the method of sounding the upper air by unmanned balloons, and, as a preliminary attempt, dismissed from Paris a number of small balloons, a large proportion of which were recovered, having returned to earth after less than 100 miles' flight. Larger paper balloons were now constructed, capable of carrying simple self-recording instruments, also postcards, which became detached at regular intervals by the burning away of slow match, and thus indicated the path of the balloon. The next attempt was more ambitious, made with a goldbeaters' skin balloon containing 4,000 cubic feet of gas, and carrying automatic instruments of precision. This balloon fell in the Department of the Yonne, and was returned to Paris with the instruments, which remained uninjured, and which indicated that an altitude of 49,000 feet had been reached, and a minimum temperature of -60 degrees encountered. Yet larger balloons of the same nature were then experimented with in Germany, as well as France.

A lack of public support has crippled the attempts of experimentalists in this country, but abroad this method of aerial exploration continues to gain favour.