AER 



AES 



of that metal, because the heat attending 1 

 the effervescence will be diminished, and 

 the diluted acid will pass more readily 

 through the interstices of the turnings, 

 when they are heaped together, than 

 through the filings, which stick closer to 

 one another. The weight of the hydro- 

 gen gas thus obtained by means of sul- 

 phuric acid is, in the common way of 

 procuring it, generally one-seventh part 

 of the weight of common air ; and with the 

 necessary precautions for philosophical 

 experiments, less than one-tenth of the 

 weight of common air. We shall con- 

 clude this article with a description of 

 some figures explanatory of the subject. 

 Figure 1 (plate Aerostation) represents a 

 balloon, 13 F, suspended by means of the 

 poles G and H, and the cord, for the pur- 

 pose of being filled with gas. It is kept 

 steady and held down whilst filling by 

 ropes, which are readily desengaged. A, 

 A, are two tubs, about three feet in diam- 

 eter, and two feet deep, inverted in larger 

 tubs, B, B, full of water. At the bottom 

 of each of the inverted tubes there is a hole 

 in which is inserted a tin tube ; to these 

 the silken tubes of the balloon are tied. 

 Each of the tubs, B, is surrounded by se- 

 veral strong casks, so regulated in num- 

 ber and capacity, as to be less than half 

 full when the materials are equally distri- 

 buted. In the top of these casks there 

 are two holes : to one of which is adapted 

 a tin tube, formed so as to pass over the 

 edge of the tub B, and through the water, 

 and to terminate with its aperture under 

 the inverted tub A. The other hole, 

 which serves fur supplying the cask with 

 materials, is stopped with a wooden plug. 

 "When the balloon is to be filled, the com- 

 mon air is first to be expelled, then the 

 silken tubes are fastened round the tin 

 ones ; the iron filing's are to be put into 

 the casks, then the water, and lastly the 

 sulphuric acid. The balloon will speedi- 

 ly be inflated by the gas, and support it- 

 self without the aid of the rope G H. As 

 the filling advances, a net is adjusted 

 about it, the cords proceeding from the 

 net are fastened to the hoop MN; the 

 boat I K is suspended from the hoop, and 

 whatever is wanted for the voyage is de- 

 posited in the boat. When the bailoonis 

 sufficiently full, the silken tubes are sepa- 

 rated from the tin tubes, their extremities 

 are tied, and they are placed in the boat. 

 When the aeronauts are seated in the 

 boat, the ropes that held the balloon down 

 are slipped oft', and the machine ascends 

 in the air, as in figure 2. In fig. 3, is a 

 representation of a part of Mr. Garnerin's 



balloon in its ascent, to which is attached 

 a parachute, in its contracted state, and 

 below is the car. Figure 4 shews the 

 manner in which Mr. Garnerin descended 

 in the car by means of the expanded para- 

 chute, after he had detatched it from the 

 balloon. In fig-ure 5 is represented an ap- 

 paratus, as described by Mr. Cavallo, for 

 filling balloons of the size of two or three 

 feet in diameter with hydrogen gas, after 

 passing it through water. A is a bottle, 

 with the ingredients ; BCD a tube fasten- 

 ed in the neck at B, and passing through 

 C, the cork of the other bottle, in which 

 there is a hole made to receive the tube, 

 and to this the balloon is tied. Thus the 

 hydrogen gas, coming out of the tube D, 

 will pass first through the water of the 

 bottle E, and then into the balloon. Two 

 small casks may be used instead of the 

 bottles A and E. 



-ERVA, in botany, a genus of the Mo- 

 nadelphia Decandria class and order. 

 The flowers are polygamous ; the calyx 

 five-leaved and patent : the stamina are 

 five ; the pistillum is a globulous ovary, 

 having a filiform style, terminated by a 

 bifid stigma : the fruit is an oblong, sin- 

 gle-seeded capsule, encompassed by a ca- 

 lyx : there is but one species, viz. JE. 

 aegyptiaca, or tomentosa, which grows on 

 the sandy calcareous soil of Arabia. 



JESCHYNOMENE, a word from the 

 Greek, signifying to be ashamed, because 

 it retreats from the touch : bastard sensi- 

 tive plant, in botany, a genus of the Dia- 

 delphia Decandria class and order, and of 

 the natural order of Papilio Naceae, of 

 which there are 12 species, found native in 

 the East Indies, and cultivated in other 

 hot countries. One of the species may be 

 treated as hemp, and is used for the same 

 purposes. 



AESCULUS, in botany, a genus of the 

 Heptandria Monogynia class and order, of 

 jthe natural order of Trihilatse. There 

 are three species : the first, or common 

 horse-chestnut, was brought from the 

 northern parts of Asia into Europe about 

 the year 1550, and sent to Vienna about 

 the year 1558. From Vienna it was con- 

 veyed to France and Italy ; but it came to 

 u from the Levant. It is distinguished 

 by the beautiful parabolic form of its 

 branches, the disposition and structure of 

 its digitate leaves, and by the pyramidal 

 bunches of its white flowers, variegated 

 near the centre with yellow or red. Al- 

 though this tree is now less in esteem for 

 avenues and walks than it formerly was, 

 on account of the early decay of its leaves. 

 it affords an excellent shade; and th" 



