] 58 Royal Society. 



be made which will occupy much time ; yet, not wishing to postpone 

 the publication of certain facts, I purpose now to give a short account 

 of them, to be extended and completed on a subsequent occasion*. 



In the first place it is important to remark that the olivine of me- 

 teorites contains most excellent "glass-cavities," similar to those in 

 the olivine of lavas, thus proving that the material was at one time 

 in a state of igneous fusion. The olivine also contains " gas-cavities," 

 like those so common in volcanic minerals, thus indicating the pre- 

 sence of some gas or vapour (Aussun, Parnallee). To see these 

 cavities distinctly, a carefully prepared thin section and a magnifying 

 power of several hundreds are required. The vitreous substance 

 found in the cavities is also met with outside and amongst the crys- 

 stals, in such a manner as to show that it is the uncrystalline residue 

 of the material in which they were formed (Mezo-Madaras, Par- 

 nallee). It is of a claret or brownish colour, and possesses the cha- 

 racteristic structure and optical properties of artificial glasses. Some 

 isolated portions of meteorites have also a structure very similar to 

 that of stony lavas, where the shape and mutual relations of the 

 crystals to each other prove that they were formed in situ, on solidi- 

 fication. Possibly some entire meteorites should be considered to 

 possess this peculiarity (Stannern, New Concord), but the evidence 

 is by no means conclusive, and what crystallization has taken place 

 in situ may have been a secondary result ; whilst in others the con- 

 stituent particles have all the characters of broken fragments (L'Aigle). 

 This sometimes gives rise to a structure remarkably like that of con- 

 solidated volcanic ashes, so much, indeed, that I have specimens 

 which, at first sight, might readily be mistaken for sections of meteor- 

 ites. It would therefore appear that, after the material of the me- 

 teorites was melted, a considerable portion was broken up into small 

 fragments, subsequently collected together, and more or less consoli- 

 dated by mechanical and chemical actions, amongst which must be 

 classed a segregation of iron, either in the metallic state or in com- 

 bination with other substances. Apparently this breaking up oc- 

 curred in some cases when the melted matter had become crystal- 

 line, but in others the forms of the particles lead me to conclude 

 that it was broken up into detached globules whilst still melted 

 (Mezo-Madaras, Parnallee). This seems to have been the origin of 

 some of the round grains met with in meteorites ; for they occasion- 

 ally still contain a considerable amount of glass, and the crystals 

 which have been formed in it are arranged in groups, radiating from 

 one or more points on the external surface, in such a manner as to 

 indicate that they were developed after the fragments had acquired 

 their present spheroidal shape (Aussun, &c). In this they differ 

 most characteristically from the general type of concretionary globules 

 found in terrestrial rocks, in which they radiate from the centre ; 

 the only case that I know at all analogous being that of certain 

 oolitic grains in the Kelloways rock at Scarborough, which have 

 undergone a secondary crystallization. These facts are all quite 

 independent of the fused black crust. 



* The names given thus (Stannern) indicate what meteorites I more particu- 

 larly refer to in proof of the various facts previously stated. 



