Real and supposed effects of igneous action. 349 



form, to those that are bhiwn up into innumerable cavities, 

 scarcel)' connected by the thinnest partitions, hke the mem- 

 branes between the air cells and blood vessels of the lungs, 

 and having vastly more pore and space than solid matter. — 

 In many pieces, the cavities are so large, that the thumb is 

 easily introduced, and we perfectly understand how to con- 

 ceive of those volcanic caverns described by Mr. Goodrich 

 and the other Missionaries, and which are occasionally large 

 enough to be used as cemeteries, or as refuges from hostile 

 pursuit, or as habitations. Sintilar caverns in lava are nu- 

 merous, as is well known, in the Azores, and in Iceland, and 

 other distinguished volcanic regions. 



Among the cavities in the vesicular lava of Kirauea, there 

 is the most beautiful exhibition of colors that can be imagin- 

 ed. The surface is glossy, as if covered with the most per- 

 fect enamel or varnish, and the iris and columbine hues are 

 richly displayed by every change of position. This splendid 

 effect is undoubtedly due, chiefly, to the large dose of iron, 

 and the very perfect nianner in which the intense heat has 

 blended its oxides with the other materials. 



9. Fine spun volcanic glass. — This exists sometimes in 

 masses which are scarcely coherent, and seem like what they 

 evidently were originally, congealed froth and foam, the float- 

 ing scum of igneous fluidity. Their color is like that of 

 olivin. 



The most interesting form is that of fine filaments, resem- 

 bling spun glass, bundled together in confused masses of in- 

 coherent fibres. Among them are portions of a dark color 

 and firmer texture, of a tadpole shape, and very strongly re- 

 sembling Prince Rupert's drops ; only they are much small- 

 er, and the fracture of the bulbous part which takes place 

 on breaking the stem, seems to result more from y crushing, 

 than an explosion of the mass ; so that we cannot say that 

 they are formed like Prince Pvupert's drops ; doubtless the 

 bath in which they were suddenly congealed was air, althongh 

 it its possible, that water might have been, at least in some 

 cases, concerned. It is this filamentous glass that is mention- 

 ed by Mr. Goodrich in his letter, (Vol. XI. pa. 2.) as being^ 

 blown away by the winds and carried to the distance of 

 many miles from the voicanos. 



