120 SOLID VOLCANIC PRODUCTS. 



in the side of the mountain ; and many inhabitants were swept away in the 

 waters, or buried under deposits of mud, during the 8th and 12th days of 

 October. 



Muddy eruptions of Quito. The volca.ns of Peru, which like those of Java 

 have rarely produced lavas, vomit from their sides torrents of mud called 

 inoya, sometimes sulphurous like the buah of Java, at others carboni'ferous. 

 This happened in 1698, when the volcan of Carguarai'zo crumbled, covering- 

 more than 2500 square rniles with mud ; and in 171)7, when the village Pel- 

 lile'o, near Rio-Bamba, was buried under a mass of black mud, &c. What 

 especially characterizes the eruptions in Peru, and makes them very strange, 

 is that the muddy waters which spring from the bosom of the earth, are 

 filled with small fishes, species of which live in the neighbouring lakes; and 

 '.he quantity of them has been sometimes so great as to excite epidemic dis- 

 tases by their putrelactiori. 



Gases disengaged from Lavas. It can be readily conceived that gases 

 and matters of various kinds may be disengaged from the bowels of the 

 earth, through fissures communicating with its surface; but what is most 

 remarkable, they are also disengaged from lavas, although on leaving the 

 volcano they have no properties in common. As long as the lava is fluid 

 and at a high temperature nothing escapes from it, but the moment it begins 

 to harden, and consequently to cool, gases are disengaged in more or less 

 quantity. Streams, matters which filled the lowest level?, then constantly 

 emit the vapour of water, hydrochloric acid, sal ammoniac, which are de- 

 posited on the surface, to say nothing of realgar, iron, &.c., which are some- 

 times sublimed in the fissures or cracks. Consequently the lava itself must 

 contain these matters, which remain engaged in it, we know not how, while 

 vhe mass is fluid or pasty, and \vhich are disengaged just in proportion as 

 it solidifies and cools, and in a manner whieh leaves no after-trace. It is 

 supposed that all these matters give to porous lavas, the power of preserving 

 their fluidity for a much longer time than similar substances artificially 

 prepared. 



39. Solid products of Volcanoes. All the solid substances which 

 volcanoes produce in great abundance, belong to the group of si'li- 

 cates, generally anhy'drous si'licates, and particularly to that divi- 

 sion of those confounded under the name of feldspar. These are 

 generally compound rocks, and substances more or less mixed, the 

 principal base of which it is difficult to separate, and therefore 

 they cannot be accurately classified : we are forced to resort to 

 artificial divisions. 



1st. Tra'cltyte (from the Greek trachus, rough) is a rock often 

 rough to the touch, as its name indicates, composed of albite or 

 rya'colite, sometimes compact, of a ceroid or vitreo-resinous, and 

 occasionally earthy lustre, sometimes crystalline, the mass being 

 finely porous, containing crystals of the same substances, and often 

 also hornblende and black mica. 



Albite (from the Latin, albus, white), a mineral so called from its colour, 

 which contains si'lica, alu'mina, and soda. A lamellar variety is found at 

 Chesterfield, Mass., called Cleavelandite, in honour of Professor Cleaveland. 



Rya'colite (from the Greek, ruax, a stream, and litkos, stone), is a glassy 

 mineral, of a greyish-yellow to white colour, or colourless. Besides si'lica, 

 alu mina, and soda, rya'colite contains potash. 



39. What are the general characters of the solid products of volcanoes 7 

 What is tru'chytc 1 



