JE R O 



ing Table exhibits the weight in French grains necessary to separate 



each metal from the mercury. 



Gold , 416 Zinc ,.. 204 



Silver 429 Copper 142 



Tin 418 Antimony 126 



Lead 397 Iron 115 



Bismuth 372 Cobalt 8 



Platinum 282 



JER AS, list of the most remarkable : Julian 



Period. B.C. 



Creation of the world 706 4007 



Deluge 2362 2351 



Olympiads of the Greeks 3937 776 



Rome built, or Roman sera 3961 752 



JEra of Nabonassar of Chaldaens and Egyptians 3967 746 



Death of Alexander 4390 323 



^EraoftheSeleucidae 4401 312 



First of Julius Caesar 4669 44 



Vulgar sera of Christ's birth 4713 A. C, 



Hegira, Mahometan aera 5335 622 



Yesdegird, Persian sera 5344 631 



JERONAUTICS. 



To calculate the height to which a balloon will ascend, under given 

 circumstances. ( WrigliVs solut. Camb. Prol.) 



Let W weight of the balloon, and all its appendages in ounces, D 

 density of mercury at the time, 5 the spec. grav. of the atmosphere at 



the surface of the earth, when the barometer stands at 5 feet, and that 



n 



of the gas ; c the capacity of the balloon in cubic feet, x = height to 

 which it will ascend in feet j then 



b D n $ c3 



X Jog. 



- a 



Cor. If the gas be hydrogen or n = I 3, b 30 inches = -^ feet, D = 

 14019 (density of water being 1000), and S = -, then 



* = 12057 x log. Tg^gjr 



lr. Given W = 20 stone, and the other elements as in the Cor. to de- 

 termine the magnitude of the balloon necessary just to lift that weight 

 from the ground. 



/, c 3 4011 cubic feet, 



7 



