872 APPENDIX. 



solid. It is important to diminish as much as possible the number of 

 tbe sections of tbe cloth composing the balloon, and this can be done 

 by having it woven especially for the purpose ; it is also necessary 

 that the greatest care should be taken to insure regularity in cutting 

 them. The joinings should be covered with bands of varnished cloth, 

 but these bands should be made as thin as possible. 



It is also advisable to strengthen the head of the balloon round the 

 valve. For this purpose two coverings of the cloth should be used, 

 with a lining of caoutchouc between them, the whole covered with 

 muslin. This might be woven specially, just as a cotton night-cap is 

 made, and extended to a distance of two metres from the valve in 

 spherical sections, arranged in divisions of four or six, as might be 

 deemed advisable. 



All the parts of the balloon in the neighborhood of the valve should 

 be varnished internally and externally, to avoid escape of gas by the 

 seams. 



The valve should be constructed according to the system of M. Gif- 

 fard, but should be very much lighter. A model of this valve has 

 been made by M. Comme, and is to be seen at No. 50 Rue Rodier, 

 Paris, at the Exhibition of the Meteorological Academy. 



The netting should be constructed in the ordinary manner. 



It is not necessary to suppress the knots, and yet if means could be 

 found to execute this part of the work without them it would be found 

 advantageous. It is not absolutely necessary to have a safety valve. 

 It would be preferable to terminate the neck of the balloon by an 

 arrangement of the cloth susceptible of being hermetically contracted, 

 and to which the aeronaut could easily ascend. 



There is no means of dispensing with the use of hydrogen gas as 

 the ascending power, and this necessitates the transportation of a large 

 quantity of sulphuric acid, — say from seven to eight thousand kilo- 

 grammes for every thousand cubic metres. It would be possible to 

 diminish this quantity by taking the acid, carefully rectified, or even 

 by taking anhydric acid, if the cost be not too great. The iron ought 

 to be in shavings and not in dust. A portion of them should be taken 

 in boxes or barrels not liable to oxydation, which would cause a loss 

 of the acid and of the weight. Before the iron is used it should be well 

 brushed or shaken. 



For generators wine or spirit casks which have already served for 

 these liquids can be used with advantage, if care be first taken to 

 see that they do not leak. It would also be advisable to use the 

 apparatus called VappareU de engagement continu, employed by M. 



