46o Royal Society. 



mode of aggregation, it is generally discovered in al! the 

 pieces of the same substance, and it is this which may 

 serve as a character for recognising it. 



Minerals in which there is wanting some one of the 

 sections nticessary for completing the primitive form, pre- 

 sent a fracture properly so called at the place where these 

 sections ought to exist. For example, in the amphibole, 

 the joints parallel to the panes of the prism are very di- 

 stinct, whereas we perceive none in the direction of the 

 bases ; so that the crystal is broken, instead of allowing 

 itself to* be divided in the same direction. There are there- 

 fore, in these cases, longitudinal joints with a transverse 

 fracture. In other cases trhe joints are parallel to the bases, 

 and the fracture is longitudinal. We shall point out the 

 different directions according to which the fracture takes 

 place; and when ihere will be no joints visible in any di- 

 rection, as takes place with respect to agate-quartz, we 

 shall say that the fracture is indefinite. 



[I'o be continued.] 



LXIX. Proceed'mgs of Learned Societies. 



ilOYAL SOCIETY. 



JVlAY 31. — The conclusion of Mr. Home's paper on the 

 organs of q^eneration in ovi-viviparous animals, particularly 

 the squalus or shark genus, and the opossum, was read. 

 Mr. H.*s observations chiefly applied to the squalus acan- 

 ihius, or picked dog-ti.sh, conimon on the shores of Nor- 

 folk; a.id the kangaroo, particularly the latter, the young 

 of which not deriving its nutriment by a navel-string, or 

 from the uterus of its mother, is supported by external 

 agents, of which air forms an essential part. He also no- 

 ticed the fact, that fish deposit their eggs on rocks and 

 plants near the surface of the water, which there contains 

 ■more atmospheric air, and thkt this air is necessary to the life 

 of the young fish, which are enveloped in a gelatinous fluid. 

 June 7, — was occupied in reading Mr. Brande's appen- 

 dix to Mr. Home's paper, consisting of a chemical analysis 

 of the peculiar gelatinous-like matter in which the ova of 

 sharks, spawn of frogs, &c. are nourished. By the friendly 

 assistance of Sir Joseph Banks, Mr. B. obtained some of 

 what is called star-shot jelly from Lincolnshire (that sub^ 

 stance found near marshes, which Mr. Pennant justly con- 

 jectured to be the excrement of herons after feeding on 

 frogs) ; the matter which envelops frog-spaAn, and that 



which 



