APPENDIX. 



APPENDIX A. {See page 48.) 



Translation of the Opinion of M. Wilfrid tie Fonvieille, Aeronaut, as 

 to the Best Manner of preparing Balloons for Use in the Polar 



Reg in us. 



The captive balloon established by M. Henry Giffard last summer 

 in the courtyard of the Tuilleries may be considered as offering the 

 type which the constructors of balloons intended for use in the Polar 

 explorations should adopt for model. But in reducing considerably 

 the proportions (which would be absolutely necessary) it becomes in- 

 dispensable to introduce in the construction of such balloons important 

 modifications which will necessarily be expensive. 



It would be imprudent to construct a balloon capable of resisting 

 powerful winds without employing two silk coverings, between which 

 should be placed a strong lining of caoutchouc. The external covering 

 of silk can be made much lighter than the other. This should be cov- 

 ered in its turn by a thin coating of caoutchouc, covered again by 

 muslin varnished over with common flaxseed oil. The balloon of M. 

 Giffard was composed of two linen coverings separated by a lining of 

 unvulcanized India rubber. The two linen coverings can be replaced 

 by two silk tissues, but it is impossible to suppress the external coat of 

 India rubber, which is intended to prevent the oil from penetrating 

 inside and attacking the non-vulcanized rubber as well as the silk 

 covering, which gives to the balloon all its power of resistance, and 

 which, combined with the caoutchouc, imparts to the whole a sufficient 

 elasticity. 



But little reliance should be placed on the combinations so impru- 

 dently eulogized by aeronauts, but more especially on the so-called 

 Meudon varnish, about which the officers of the Engineers make such 

 a mystery. 



The seams should be worked by hand, and should be made very 



