Henslow, Prof., on chalcedony.
Hoffmann, on decomposed trachyte.
Holland, Dr., on Iceland.
Horner, Mr., on a calcareo-animal substance. -on fusibility of feldspar.
Hubbard, Dr., on dikes.
Humboldt on ejected fragments. -on obsidian formations. -on parapets round craters. -on sphaerulites.
Hutton on amygdaloids.
Hyalite in decomposed trachyte.
Iceland, stratification of the circumferential hills.
Islands, volcanic, distribution of. -their elevation.