GEOGNOSY AND GEOLOGY. 913 
Leucitophyr lava consists of a combination of augite with leucite, in 
which sometimes one substance prevails and sometimes another. It is the 
same leucitophyr whose petrographical character we have already become 
acquainted with. It likewise embraces many other minerals which are not 
essential to its composition, as zeolite, sodalite, mica, micaceous iron, nephe- 
line, harmotome, &c. ; it occurs both crystalline and stony. The crystalline 
leucitophyr often contains perfect crystals (trapezohedra), whose tolerably 
equal dimensions and light color contrast remarkably with the black prisms 
of the augite. 
The term “volcanic ejectamenta” includes everything thrown into the 
air by volcanic forces. They are of very different character, and vary not 
only in different volcanoes but in different eruptions of the same volcano. 
Under this head belong pieces of lava torn off from the interior of the 
throat or mouth of the volcano, and hurled out during the eruption ; also, 
the so-called bombs or spheroidal lava masses, which, ejected into the air, 
have had a rotary motion communicated to them, and cool before reaching 
the ground. The form of these bombs is that of elliptical spheroids elevated 
at the equator and flattened at the poles, presenting a miniature resemblance 
to the terrestrial globe. Additional substances thrown out of the volcano are 
lava gravel; volcanic sand, consisting of crystalline particles of volcanic min- 
_erals ; volcanic ashes, consisting of the dust of ground up rocks; volcanic 
threads produced from the lava like fine fibres from molten glass; finally, 
blocks of foreign rock species, as granite, gneiss, mica slate, dolomite, sand- 
stone, and limestone, the latter, when inclosed by the lava, being partially or 
entirely converted into marble. These ejectamenta, after being deposited in an 
appropriate location, are frequently so acted upon by water as to become con- 
verted into volcanic conglomerate and volcanic tufa. ‘They then ‘appear stra- 
tified, and are distinguished according to the character of their components 
into trachyte conglomerate, trachyte tufa, basalt conglomerate, leucitophyr, 
conglomerate, and leucitophyr tufa; these, not unfrequently, are broken up 
into conspicuous rocks by subsequent convulsions, and are sometimes traversed 
by veins of lava. 
Volcanic mud is produced by the union of volcanic ashes or dust with 
water, which, vaporiform while escaping from the mouth of the volcano, be- 
comes condensed in the higher regions. of the atmosphere, and descends in 
the form of rain, accompanied by thunder and lightning. Currents are 
sometimes produced under such circumstances, sufficient to devastate 
extended regions. These muddy waters not unfrequently accumulate in 
subterranean cavities ; and by means of fissures in the sides of the mountains, 
are allowed to escape into the lower lands. According to Humboldt, dis- 
charges of mud never take place in the same manner as laya. The subter- 
ranean lakes sometimes contain a great number of fish, which are discharged 
with the water in which they live. These fish are, however, not peculiar to 
the subterranean waters, being found in the superficial lakes and streams. 
Thus Arges cyclopwm, Val. (Pimelodus cyclopum, Hnumb.), and Brontes 
prenadilla, Val., are emitted from the volcanoes of Tunguaragua and Cotopaxi 
in South America. 
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