You've converted the absolute value, not the delta.
The quickest in your head conversion of a delta °C --> delta °F is to simply multiply by 2. +4°C --> +8°F
To be accurate, remove 1/10^th^ of the °C value before the multiplication. +4°C --> (4 - 0.4) = 3.6 ---> +7.2 °F
For absolute values, I personally do, for a quick 'in your head' approximation the other way round (°F --> °C) :
- remove 32 °F (78°F --> 46)
- divide by 2 (46 --> 23°C; I may stop there for a very rough approximation)
- add 1°C per decade (if you got 23°C, add 2°C --> 25°C; I usually stop there)
- add 0.1°C per unit (25 --> 25.5°C; it's not the exact result but not too far)
The parachute was covering the top of the balloon. It remained in position once the balloon deflated, and allowed to fall gently. There were several demonstrations, I think; people were crazy about ballons back then and experimented a lot of things.
Here is one one of the accounts in French, published in Le Républicain's edition from Aug 12, 1894 :