Sept. 3, 1885] 
NALFURE 
421 
photographs were taken at greater altitudes—one at 1000, 
and one at 1100 metres. Hence in crossing Paris, between 
1.40 and 2.12, or in twenty-two minutes, five photographs 
were obtained. It would be easy to have two or three 
photographic apparatus with an operator in the car for 
each, and thrs to obtain a series of views. By this 
method a series of topographical documents of incom- 
Fic. 2.—Explanatory plan of above :—1. Gate of the Hétel de Ville. 
Quay of Hétel de Ville. 3. Rue de Brosse. 4. Old Lobau Barracks. 
5. Rue de l’Hotel de Ville. 6. Louis Philippe Bridge. 7 and 8. Baths. 
g. Rue de Bellay. 1o. Quai de Bourbon. 11. Quai d’Orleans. 12. 
Pont St. Louis. 13 and 14. Boats. 15. Pier. 
parable precision might be obtained. Amongst the views 
taken during this ascent those which are perfect in point 
of clearness are those taken at the moment when the rays | 
of the sun fell directly on Paris. Good light is absolutely 
indispensable, and, in spite of the photographs being 
instantaneous, the car should be kept perfectly free from 
oscillation at the moment the picture is being taken. 
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The operator and occupants of the car must at that 
moment remain perfectly still. The movement of the 
balloon has no injurious effect on the clearness of the 
proofs obtained ; in the present instance the current of 
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Fic. 3.—Arrangement of photographic apparatus in the balloon. 
air was somewhat rapid, for the balloon traversed Paris 
at its greatest width, 11 kilometres, in thirty-two minutes. 
The rapidity of the wind increased subsequently to much 
more than this. After taking photographs of the earth 
below, the apparatus was turned upwards to obtain views 
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Fic. 4.—Diagram of the ascent of the ‘‘ Commandant Riviére ” 
of the clouds ; but the white clouds which reflect the rays 
of the sun with great intensity, did not give good results. 
The apparatus will require special arrangement for this 
work, and in their next expedition the aéronaut-photo- 
graphers hope to obtain something more complete than 
they have done. Their experience on the whole is that 
photographs may be obtained in a balloon as beautiful 
and clear as the best produced on ¢erra firma. Thanks | 
balloon from Paris to Les Rozais, near Rheims, June 19, 1885. 
to the instantaneous process, to the extra-sensitive plates 
produced to-day, and to other modern improvements, 
aérostatic photography has a great future. It will give 
plans which will exceed in precision and clearness the 
most pains-taking maps; it will be a powerful ally of 
military art, for it will admit of obtaining a reliable plan 
of fortresses or of hostile works. At a height of 600 
metres a balloon has nothing to fear from artillery fire, 
