The balloons, which were constructed to contain about 70,000 cubic feet, were generally inflated with ordinary coal-gas. The bags of letters and despatches were firmly fixed outside the car. Higher up was secured a cage containing carrier-pigeons, intended to bring back news and replies to the outgoing letters.
I have endeavoured to learn some particulars about the pigeons employed, but, owing to the disturbed state of Paris, I have obtained but little information beyond that which has appeared in the newspapers. R. W. Alldridge, Esq., of Charlton, however, informs me that the pigeons used for the postal service during the siege were birds of a composite race and of no particular breed; their prominent characteristics were those of the Antwerp strain, the Antwerp itself being the produce of a variety of races of no intrinsic value.
In remarking that fancy pigeons may be produced of any colour or mark, and almost of any variety of feather, Mr. Alldridge assures me, from his own experience, that it is equally possible to regulate their intellectual development, and that these birds can be produced with different powers of orientation to meet the requirements of particular cases. The bird required to make journeys under 50 miles would materially differ in its pedigree from one capable of flying 500 or 600 miles. Attention in particular must be given to the colour of the eye: if wanted for broad daylight, the bird known as the "Pearl-eye," from its colour, should be selected, but if for foggy weather or for twilight living, the black or blue-eye bird should receive the preference.
It can hardly, therefore, be matter of surprise that so many pigeons failed to return to Paris.
It was necessary to resort to special methods of preparing the return document which would have been otherwise too heavy and voluminous for their power of carriage. Photography was equal to the occasion, and long letters were reduced to within an area not exceeding one or two square inches on paper of the thinnest texture. These slips were sometimes rolled around the central feather of the bird's tail, being firmly secured about the shaft towards its base; at other times the despatches were wrapped around the legs of the bird; but generally they were enclosed inside a quill, and fastened to the central feather of the tail; the central feather is chosen, because it remains
