Undeterred by these disasters, a notable escape was now attempted. An important total eclipse of the sun was to occur in a track crossing southern Spain and Algeria on December 22nd. An enthusiastic astronomer, Janssen, was commissioned by the Academy of Sciences to attend and make observations of this eclipse. But M. Janssen was in Paris, as were also his instruments, and the eclipse track lay nearly a thousand miles away. The one and only possible mode of fulfilling his commission was to try the off-chance afforded by balloon, and this chance he resorted to only twenty days before the eclipse was due.

Taking with him the essential parts of a reflecting telescope, and an active young sailor as assistant, he left Paris at 6 a.m. and rose at once to 3,600 feet, dipping again somewhat at sunrise (owing, as he supposed, to loss of heat through radiation), but subsequently ascending again rapidly under the increased altitude of the sun till his balloon attained its highest level of 7,200 feet. From this elevation, shortly after 11 a.m., he sighted the sea, when he commenced a descent which brought him to earth at the mouth of the Loire. It had been fast travelling--some 300 miles in little more than three hours--and the ground wind was strong. Nevertheless, neither passengers nor instruments were injured, and M. Janssen was fully established by the day of eclipse on his observing ground at Oran, on the Algerian coast. It is distressing to add that the phenomenon was hidden by cloud. In the month that followed this splendid venture no fewer than fifteen balloons escaped from Paris, of which four fell into the hands of the enemy, although for greater security all ascents were now being made by night.

On January 13th, 1871, a new device for the return post was tried, and, in addition to pigeons, sheep dogs were taken up, with the idea of their being returned to the city with messages concealed within their collars. There is apparently no record of any message having been returned to the town by this ingenious method. On January 24th a balloon, piloted by a sailor, and containing a large freight of letters, fell within the Prussian lines, but the patriotism of the country was strong enough to secure the despatches being saved and entrusted to the safe conveyance of the Post Office. Then followed the total loss of a balloon at sea; but this was destined to be the last, save one, that was to attempt the dangerous mission. The next day, January 28th, the last official balloon left the town, manned by a single sailor, carrying but a small weight of despatches, but ordering the ships to proceed to Dieppe for the revictualling of Paris.

Five additional balloons at that time in readiness were never required for the risky service for which they were designed.

There can be little doubt that had the siege continued a more elaborate use of balloons would have been developed. Schemes were being mooted to attempt the vastly more difficult task of conveying balloons into Paris from outside. When hostilities terminated there were actually six balloons in readiness for this venture at Lisle, and waiting only for a northerly wind.