A E R

A F F

( n )

the composition and probably the external cha-racters would have been strictly analogous tothose of the other aerolites.

II. On the 22d of May 1809,“ an aerolite,or rather several, fell at Stannern in Moravia .Of the circumstances attending its fall there isno published account; the following are theexternal characters of a specimen in the pos-session of the Count d’Unin, and procured byhim on the spot. Its external surface is black,and shows evident signs of fusion. Internallyit presents a pale ash-grey earthy base in whichare disseminated some concretions of a darkercolour, and more compact than the rest of themass ; a few dispersed grains of pyrites are alsovisible. The entire stone is tender, friable, andits specific gravity is 3. 19. It is not attracted bythe magnet, but before the blow-pipe it fuseswith difficulty into a black glass, which is thenacted on by the magnet. On digestion in mu-riatic acid it affords a very small quantity ofsulphuretted hydrogen. It has been analysedby Klaproth, by M. Moser of Vienna , and byVauquelin. The particulars of Klaproth ’s ana-lysis we are unacquainted with, being onlyinformed in general that tire composition of thisaerolite bears a strong resemblance to that ofbasalt. Vauquelin ’s analysis, which was per-formed with much care, gives the followingconstituent parts of the entire stone.

50. silex12. lime9. alumine29. oxide of ironI. oxide of manganese

nickel and sulphur, of each a trace.

101 .

Hence it appears that the Moravian aeroliteis specifically different from all those that havehitherto been described, by the absence of mag-nesia, and the presence of lime and of alumine.

12. The last meteoric stone b that we shallmention is one that fell near Sigena in Arragon ,in the year 1773, and was deposited in the royalmuseum at Madrid . In 1805 M. Proust ob-tained leave to analyse a portion of it, and topublish the result, with a description of thestone. Its present weight is 6 lbs lOoz. butseveral fragments have been broken from it:where the surface is unbroken it presents theblack vitreous crust which is characteristic ofmost of these bodies. Its colour internallyis a light bluish grey. It is an aggregate ofa Ann. de Chim. Ixx. 321. * Jouru. de Phys.

globular concretions the largest of which arescarcely bigger than hemp-seeds, and which onexamination with a lens are evidently coveredover with extremely minute crystalline points.Intermixed irregularly with these concretionsare particles of bronze coloured pyrites and ofmetallic matter. On pulverizing portions ofthe stone, and separating by the magnet themetallic particles, their proportion to the restof the mass was found to vary from 17 to 22per cent. This metallic matter was an alloy ofiron and nickel in the proportion of 97 of theformer to about 3. of the latter. The rest ofthe stone, including the pyrites, was then ana-lysed and afforded by the usual methods,

12. sub-suiphuret of iron5. black oxide of dittoG6. silex20. magnesia

103.

The excess of weight ill this as in the pre-ceding cases is no doubt to be attributed to theoxidation of the iron.

AFFINITY.

M. Berthollet, one of the most profound andeminent chemical philosophers of the age, hasendeavoured to shew that it is the tendency ofehemical affinity to combine bodies in all pro-portions, so that where any limits to this in-definite combination appear, they arise fromthe operation of circumstances distinct fromchemical affinity, which essentially modify itsaction.

On the other hand it is advanced by manymost ingenious chemists, and supported by adaily encreasing body of experiments, that sub-stances unite in proportions which are rendereddefinite by the sole operation of their mutualaffinity, and are equally definite whether onlyone or more compounds of the same bodiesexist.

To this opinion, which has been advancedby Richter, Proust, and other eminent che-mists, Mr. Dalton* has added a most importantrule (supported by a variety of striking examples)which is, that where two bodies combine indifferent proportions, if the quantity of one ofthem be assumed as a fixed number, the pro-portions of the other body that unite to it arein the simplest possible ratio to each other, be-ing produced by multiplying the lowest propor-tion by a simple integral number as g, 3, 4, &c.

Thus for example, if a metal can combine

1805. « New System of Chemical Philosophy.

B2