CONSTITUENTS OP AEROLITES. 



In some exceptional cases the iron contained in these masses 

 differs extremely in its proportion and quality. The meteorites 

 which fell at Agram, in India those which were found at Sisim, 

 in the Jeniseisk government and those brought by Humboldt 

 from Mexico, contained so much as 96 per cent, of very 

 malleable iron, while the aerolite of Sienna did not contain 

 above 2 per cent., and those of Jonzac and Juvenas contained 

 no metallic iron at all. 



5. The crust by which meteorites are almost invariably 

 invested is only a few hundredths of an inch in thickness, and is 

 described by Humboldt as being highly characteristic. It has 

 often a pitchy lustre, and is sometimes veined. This black 

 crust is separated from the light gray mass within it by a line 

 as sharply denned as that of the dark leaden-coloured crust of 

 the white granite blocks brought by Humboldt from the cataracts 

 of the Orinoco, and which are also found by the side of many 

 cataracts in other parts of the world, as those of the Nile and 

 the Congo. It is observed by Humboldt that the greatest heat 

 of porcelain furnaces can produce nothing similar to the crust of 

 the aerolites, so distinctly and sharply separated from the 

 unaltered mass within. Appearances which might seem to 

 indicate a softening of the fragments have been occasionally 

 recognised, but in general the condition of the greater part of 

 the mass the absence of all flattening which might be pro- 

 duced by the fall and the moderate degree of heat perceived 

 on touching the newly-fallen aerolite, are far from indicating a 

 state of internal fusion during its rapid passage through the 

 atmosphere. 



6. Observations and measurements made on the magnitude 

 and velocity of these meteoric bodies supply many surprising 

 results. 



Fire-balls have been observed whose computed diameters vary 

 from 500 to 2,600 feet. The fire-ball seen at Weston, in Con- 

 necticut, U.S., on the 14th December, 1807, measured 500 feet. 

 Le Eoi observed one on the 10th July, 1771, which measured 

 about 1000 feet ; and Sir Charles Blagden estimated the 

 diameter of one observed by him on the 18th January, 1713, 

 at 2,600 feet. These measurements include, however, not only 

 the solid mass, but the igneous matter by which it may have 

 been surrounded. 



Of the meteoric masses found on the surface of the earth, the 

 largest known are those of Bahia in Brazil, and of Otumpa, 

 described by Kuben de Celis. These are from seven to seven 

 and a half feet in diameter. The meteoric stone of ^Egos 

 JPotamos, celebrated in antiquity, mentioned in the " Chronicle of 



133 



