1892] ^'J«^ [Bache. 



graphic apparatus, but to strain upward upon the controlling guys, 

 because the attachment of the guys would be made to the equator 

 of the balloon, and the weight of the dependent apparatus would 

 be close to its periphery, and therefore to the centre of the spheri- 

 cal figure of the balloon. In addition, for the purpose of increas- 

 ing the stability of the balloon at the critical moment of taking 

 a photograph, the operator would steady it with a gentle draught 

 upon the dependent cord containing the reophores, at the precise 

 point of time when he makes the electrical contact with the shutter 

 of the camera. 



I here conclude the description of that one of my proposed ad- 

 ditions to the art of photogrammetry which relates to precision of 

 results obtainable from it for a continuous line of survey, and in- 

 vite your attention for a moment to a method I suggest of using a 

 similar captive balloon in a manner which would be useful in mili- 

 tary operations. It need hardly be said that, whether captive or 

 not, balloons have heretofore been used at great disadvantage in 

 military operations, unless we except the use made of them for 

 escape, with indirect reference to those operations during the recent 

 siege of Paris. If the free aeronautic balloon passes over the 

 enemy at such a distance as to make useful what can be observed 

 from it, the glimpse is but transient, while its nearness and immense 

 volume place it in great danger. If, on the other hand, a captive 

 aeronautic balloon be used for military observation, it must ascend 

 far from the enemy, to a height which measurably neutralizes the 

 accuracy of the information sought. 



The use for military purposes of a modification of the small 

 spherical captive balloon which I have described would be con- 

 ditioned solely upon the circumstance that the wind should be blow- 

 ing towards the enemy's lines. The only change in it from the one 

 described, that would be entailed by its new purpose, would be 

 that it should be mounted with a simple network similar to that 

 which is used on the kite, and to which the string for flying it, 

 fastened similarly to the way in which it is fixed on the kite, should 

 be attached. This string, with which the balloon would be flown 

 like a tailless kite, would contain ordinary filigree reophores, 

 through whose instrumentality the photographic shutter of the 

 camera would be controlled by the operator. Lying several hun- 

 dred yards away, or even a mile or two, if desirable, outside of an 



PROC. AMER. PHILOS. SOC. XXX. 138. 2 E. PRINTED MAY 27, 1892. 



