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became necessary； as it was only in this way that the picket which it was desired to dislodge could be seen。 However； I cannot say that I thought the fire of artillery was of much effect against the unseen object； not that this was the fault of the balloon； for had it not told the artillerists which way the shots were falling their fire would have been more useless still。〃
It will be observed that at this time photography had not been adopted as an adjunct to military ballooning。
Full details have been given in this chapter of the monster balloon constructed by M。 Nadar； but in 1864 Eugene Godard built one larger yet of the Montgolfier type。 Its capacity was nearly half a million cubic feet； while the stove which inflated it stood 18 feet high； and weighed nearly 1；000 pounds。 Two free ascents were made without mishap from Cremorne Gardens。 Five years later Ashburnham Park was the scene of captive ascents made with another mammoth balloon； containing no less than 350；000 cubic feet of pure hydrogen； and capable of lifting 11 tons。 It was built at a cost of 28；000 francs by M。 Giffard； the well…known engineer and inventor of the injector for feeding steam engines。
These aerial leviathans do not appear to have been； in any true sense successful。
CHAPTER XVIII。 THE BALLOON IN THE SIEGE OF PARIS。
Within a few months of the completion of the period covered by the records of the last chapter； France was destined to receive a more urgent stimulus than ever before to develop the resources of ballooning； and； in hot haste； to turn to the most serious and practical account all the best resources of aerial locomotion。 The stern necessity of war was upon her； and during four months the sole mode of exit from Parisnay； the only possible means of conveying a simple message beyond the boundary of her fortificationswas by balloon。
Hitherto； from the very inception of the art from the earliest Montgolfier with its blazing furnace； the balloon had gone up from the gay capital under every variety of circumstancefor pleasure； for exhibition； for scientific research。 It was now put in requisition to mitigate the emergency occasioned by the long and close investment of the city by the Prussian forces。
Recognising； at an early stage； the possibilities of the balloon； an enquiry was at once made by the military authorities as to the existing resources of the city； when it was quickly discovered that； with certain exceptions to be presently mentioned； such balloons as were in existence within the walls were either unserviceable or inadequate for the work that was demanded of them。 Thereupon； with admirable promptness and enterprise； it was forthwith determined to organise the building and equipment of a regular fleet of balloons of sufficient size and strength。
It chanced that there were in Paris at the time two professional aeronauts of proved experience and skill； both of whom had become well known in London only the season before in connection with M。 Giffard's huge captive balloon at Ashburnham Park。 These were MM。 Godard and Yon； and to them was entrusted the establishment of two separate factories in spacious buildings； which were at once available and admirably adapted for the purpose。 These were at the Orleans and the Northern Railway stations respectively； where spacious roofs and abundant elbow room； the chief requisites； were to be found。 The first…mentioned station was presided over Godard； the latter by M。 Yon； assisted by M。 Dartois。
It was not doubted that the resources of the city would be able to supply the large demand that would be made for suitable material； but silk as a fabric was at once barred on the score of expense alone。 A single journey was all that needed to be calculated on for each craft； and thus calico would serve the purpose； and would admit of speedy making up。 Slight differences in manufacture were adopted at the two factories。 At the Northern station plain white calico was used； sewn with a sewing machine； whereas at the Orleans station the material was coloured and entrusted only to hand stitching。 The allimportant detail of varnish was supplied by a mixture of linseed oil and the active principle of ordinary driers； and this； laid on with a rubber； rendered the material gas…tight and quickly dry enough for use。 Hundreds of hands； men and women； were employed at the two factories； at which some sixty balloons were produced before the end of the siege。 Much of the more important work was entrusted to sailors； who showed special aptness； not only in fitting out and rigging the balloons； but also in their management when entrusted to the winds。
It must have been an impressive sight for friend or foe to witness the departure of each aerial vessel on its venturesome mission。 The bold plunge into space above the roofs of the imprisoned city； the rapid climb into the sky and； later； the pearl drop high in air floating away to its uncertain and hazardous haven； running the gauntlet of the enemy's fire by day or braving what at first appeared to be equal danger； attending the darkness of night。 It will be seen； however； that； of the two evils； that of the darkness was considered the less； even though； with strange and unreasonable excess of caution； the aeronauts would not suffer the use of the perfectly safe and almost indispensable Davy lamp。
Before any free ascents were ventured on； two old balloons were put to some practical trial as stationary observatories。 One of these was moored at Montmartre； the other at Mont…souris。 From these centres daily； when the weather permitted； captive ascents were madefour by day and two by nightto watch and locate the movements of the enemy。 The system； as far as it went； was well planned。 It was safe； and； to favour expedition； messages were written in the car of the balloon and slid down the cable to the attendants below。 The net result； however； from a strategic point of view； does not appear to have been of great value。
Ere yet the balloons were ready； certain bold and eventful escapes were ventured on。 M。 Duruof； already introduced in these pages； trusting himself to the old craft； 〃Le Neptune；〃 in unskyworthy condition； made a fast plunge into space； and； catching the upper winds； was borne away for as long a period as could be maintained at the cost of a prodigal expenditure of ballast。 The balloon is said to have described a visible parabola； like the trajectory of a projectile； and fell at Evreux in safety and beyond the range of the enemy's fire； though not far from their lines。 This was on the 23rd of September。 Two days afterwards the first practical trial was made with homing pigeons； with the idea of using them in connection with balloons for the establishment of an officially sanctioned post。 MM。 Maugin and Grandchamp conducted this voyage in the 〃Ville de Florence；〃 and descended near Vernouillet； not far beyond Le Foret de St。 Germain； and less than twenty miles from Paris。 The serviceability of the pigeon； however； was clearly established； and a note contributed by Mr。 Glaisher； relating to the breeding and choice of these birds； may be considered of interest。 Mr。 R。 W。 Aldridge； of Charlton； as quoted by Mr。 Glaisher； stated that his experience went to show 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 fifty miles would materially differ in its pedigree from one capable of flying 100 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 flying the black… or blue…eyed bird should receive the preference。〃
Only a small minority； amounting to about sixty out of 360 birds taken up； returned to Paris； but these are calculated to have conveyed among them some 100；000 messages。 To reduce these pigeon messages to the smallest possible compass a method of reduction by photography was employed with much success。 A long letter might； in this way； be faithfully recorded on a surface of thinnest photographic paper； not exceeding the