L. MECHANICS AND ENGINEERING. 451 



which carried them to the middle of the North Sea. They were 

 rescued by two brave English mariners. An interesting his- 

 tory of the balloon Louis Blanc has been published by For- 

 cot, sfivins^ an account of the ascension made durinGf tlie 

 siege of Paris in the postal service. Three balloon ascen- 

 sions during 1874 were attended with the death of the voy- 

 agers ; the first of these took place on the celebration of the 

 crowning of the King of Siam, when a slave was carried up 

 in a balloon without any provision for his safety. For scien- 

 tific applications of the balloon, meteorology takes the first 

 rank. Their usefulness in the study of the winds in the 

 midst of storms lias been forcibly urged by Janssen, who 

 has recently twice personally experienced the power of the 

 typhoon, and has also established a prize medal of gold to 

 be given to the author of the best memoir on aerostatic me- 

 teorology. A curious apparatus has been designed by Par- 

 ville for determining the true direction of the motion of the 

 clouds, with respect to the meridian. Self-recording mete- 

 orological apparatus has been invented by Messrs. Herve, 

 Manyon, Olivier, and Jobert, while minimum barometers have 

 been made by Janssen. Penaud and Godard have devised 

 apparatus to indicate the rising and falling of the balloon. 

 Croce-Spinelli and Sivel have furnished the means for ascer- 

 taining the direction of the movement of strata of air, either 

 above or below the balloon. Miss Zier, oranddauQ-hter of 

 Carcel, the inventor of the Carcel lamp, has proposed to do 

 away with the lubricating oil, whose thickening is so inju- 

 rious to the action of all self-recording apparatus at low tem- 

 peratures, by mounting the movable portions of the mechan- 

 ism on polished rubies. One of the most important improve- 

 ments in the gas balloon is that of Jobert, who proposes to 

 construct one side of the gas-holder of white, and the other of 

 black stuff", since it is easy to turn the balloon about its ver- 

 tical axis by means of a small propeller, so as to keep either 

 the black side or the white side always facing the sun, and 

 thus, by the heating or cooling, make the balloon either to 

 ascend or descend to an extent depending upon the diff*er- 

 ence in the reflecting or absorbing power of the two halves 

 of the balloon. By this means we can, perhaps, control the 

 vertical movements of the balloon to a sufiicient extent to 

 render its applications in meteorology of much importance. 



