DECENT BASALTIC ERUPTIONS. 
Ill 
the lavas — the basalts in the lava-caps — form a group by themselves wholly 
apart and distinct from all the others and with a great and well-marked in- 
terval between ; while the so-called middle-aged and modern eruptions 
shade into each other without any such distinction. 
In those volcanoes which ma}^ thus be termed middle-aged we fin d 
evidences of considerable progress of the decay which must ultimately re- 
move them altogether. The cones are still standing, indeed, but are wasted 
and worn. Their flanks are channeled deeply with ravines, and in some of 
them the interior structure is dissected and well exposed. The cinders and 
scoria have been converted into soil and the fragments have lost all resem- 
blance to their original aspects. The lava fields around them have also put on 
an appearance of antiquity ; not so great indeed as that of the massive sheets 
in the lava-caps far above them, but yet plain and conspicuous. They have 
become gray and dull in color, and the decomposition of the augites and 
feldspars has penetrated to notable depths into the solid blocks. Such are 
the cones and lava fields of the turtle-back which lies immediately north 
of Trumbull, and such are the masses which extend from the base of the 
mountain eastward. 
Let us now look at the other extreme — the extreme of recency. Between 
Logan and Trumbull we find some rather extensive fields of basalt, which 
excite surprise when we first come upon them. They are hidden by a sur- 
rounding forest of large pines, and the first view is gained either by finding 
ourselves within a dozen yards of the border, as we wander through the 
forest aisles, or else by a sudden coup d'mil, as the whole expanse flashes 
upon the vision from the summit of Trumbull. It looks as fresh as any 
coulee of Vesuvius ejected twenty or thirty years ago.* Compared with the 
other later eruptions of the Uinkaret, its dimensions are larger than the 
average. Its entire surface is covered with blocks of pumice of the most 
delicate kind. It has a texture veiy much like the lightest coke, the vesi- 
cles, however, being considerably larger than those of ordinary coke, and 
very uniform throughout. The septa between the vesicles are very thin, 
and the whole mass is so light that when a specimen is varnished over to 
*Sucli was the opinion of Mr. Holmes, who viewed it with me, and who had just returned from a 
visit to Vesuvius. 
