200 HAWATIAN ISLANDS. 
| 
Pele’s Hair ; Pele’s Hair ; Scoria, sp. | Compact vitre- Compact stony 
dark-coloured. | light-coloured. gr. 2°505. ous Lava; Lava; sp. gr. 
sp. gr. 2-91. 293. 
Ilias ss ed ae 39°74 51:19 51°93 50°67 =| 59-80 
Protoxyd of Iron, 22-99 30-26 16°91 33°62 | 31°33 
Alumina, . . . 10°55 14-07 | 
Times bid Veale sey 9 2-74 6-20 3°66 | 
Magnesia, . . . 2-40 18°16 1:73 11:33; ||) apes 
Oda; cure salts 21°62 6°31 10°52 4°83 
Waters. . <« 33 
Chlorine, . . . Trace. Trace, Trace. Trace. Trace. 
99°67 99°61 97°15 99-60 97°67 
Of the above were 
soluble in hydro- 
chloric acid, . . 48°80 49°51 45,84 42°50 24°55 
Insoluble in do. 51-20 50°49 54°16 57°50 TH45 
100-00 100-00 100-00 100:00 100:00 
The facts which have been stated afford an explanation of the dif 
ference between the two forms of lava ejections. The layers with a 
scoriaceous crust proceed from the boiling pools by overflowing; those 
mith a solid exterior, come from greater depths through fissures. The 
former have been in the process of ebullition, and, as would happen 
with any viscid fluid in this state, the surface by this action becomes 
blown up, we may almost say frothy, from inflation by the escaping 
gases. Whereas the latter come from a deeper source, where there is 
great pressure to prevent any such inflating cause from operating. 
There is the same difference that we should find between a stream 
poured from the surface of a frothy liquid, and another drawn off by 
tapping below. Itisa homely comparison; but yet may give a correct 
idea of the subject. The remarkable absence of surface scoria from the 
ejections through fissures, is thus satisfactorily explained. It should 
be remembered that the ebullition of lava arises, not from the vapo- 
rization of the heated material, as with ordinary simple liquids, but 
from the escape of gases, and principally steam, through the lava. 
