

Cee OO aa 
ade a ied . . 4 
Parti. Secr.i.§2.] LAVA-STREAMS. 295 
 yariations of temperature. He supposes that the basaltic lavas 
which have flowed so far in thin sheets, and which must have had 
a comparatively great liquidity, flowed at ‘temperatures far above that 
of their melting point, and were, to use his phrase, “superfused.” 
The varying degrees of liquidity are manifested in a character- 
istic way on the surface of lava. Thus in the great lava pools of 
Hawaii the rock exhibits a remarkable liquidity. During its ebulli- 
tion in the crater-pools, jets and driblets a quarter of an inch in 
diameter are tossed up, and, falling back on one another, make 
“a column of hardened tears of lava,” one of which (Fig. 42) was - 

Fic. 42.—CoLUMN FORMED OF CONGEALED JETS oF Liqutip Lava, CRATER OF 
Kinavea (Dana), 
found to have attained a height of 40 feet, while, in other places, the 
jets thrown up and blown aside by the wind give rise to long threads 
of glass which lie thickly together like mown grass, and are known 
by the natives under the name of Pele’s Hair, after one of their 
divinities.” 
On the other hand the lavas of Veni and of most modern 
~voleanoes, which issue so saturated with vapour as to be nearly 
concealed from view in a cloud of steam, are accompanied by 
abundant explosions of fragmentary materials, Slags and clinkers, 
torn by explosions of steam from the molten rock, are strewn 
abundantly over the cone, while the surface of the lava is likewise 
rugged with similar clinkers, which may now and then be observed 
piled up round some more energetic steam spiracle (Fig. 43). So 
vast an amount of steam rushes out from one of these orifices and 
with such boiling and explosion that the cone of bombs, slags, and 
irregular lumps of lava, forms a miniature or parasitic volcano, which 
. 
will remain as a marked cone on its parent mountain long after the 
eruption which gave it birth has ceased. The lava of the eruption 
at Santorin in 1866-67 at first welled out tranquilly, but after a few 
days its outflow was accompanied with explosions and discharges of 
incandescent fragments, which increased until they had coy ered the 
1“ Hich Plateaux of Utah,” Geog. and Geol. Survey of Territories. Washington, 
1880, chap. Ve 
ca Geol. U.S. Explor. Exped., p. 179. 
