and the other Azores. 261 
would ask Dr. Webster whether he is warranted in _infer- 
_ring that his supposed primitive specimens, “ could not have 
been subjected to a very elevated temperature,” because 
_they retain ‘ their lustre and translucency,” for the glassy 
felspar which he mentions as being found so commonly in 
the lava and even in the obsidian and pumice of St. Michael 
ds still more remarkable ‘for lustre and translucency, and in 
_ the lava of Vesuvius, we often find transparent and brilliant 
_ crystals of leucite, not to mention the beautiful olivin which 
abounds so much in the lava of the Azores. 
, The author next adverts to the occurrence of fragments 
of similar rocks, in the vicinity of volcanoes now active, 
.,and states his opinion that the specimens observed by him 
- could not have been carried up the mountain, or ‘have come 
there by design, or accident asinthe case of ballast stones, &c. 
_.. ‘These stones were not found in the immediate vicinity 
sof any, buildings, near the sea shore, nor at the base of the 
| mountain, but at an elevation of not less than one thousand 
feet. above the. level of the sea, and in a ravine, probably, 
never before trodden by human being.” We freely assent 
.to the author’s observation that “ in examining any tract of 
country,.the geologist cannot too often call to mind the re- 
mark of Humboldt that ‘“ he is exposed to a thousand er- 
rors if he loses sight of the changes, which the intercourse 
between nations produces on the surface of the globe.” 
The whole:of the lower part of the island is composed of 
“« tuff,” which also forms a smallisland, or more properly 
crater in the sea in front of the town of Villa Franca. This 
aslet. appears from, its structure to have been. formed by an 
eruption like that of 1811. Hot springs occur in’ various 
places in. St. Michael—those of * the valley of the Furnas” 
_. are,most.interesting and curious. 
ot Chap. XVIII. The Valley of the Furnas, &c. &c. The 
hot springs of the Valle das Furnas,”* render this the most 
interesting spot in St. Michael. The valley is nearly twelve 
miles in; circumference, and is bounded on every side by 
.. Moountains of various height. Its form is like that of the 
_pother enclosed vallies, which have already been described, 
oidéd nearly circular, but its surface has considerable irregu- 
»darity, rising here and there into ‘small hills. “A part of it 
is under tolerable cultivation, and ‘itis inhabited bys a ‘few 
0 a The Portuguese word §§ ‘Buenas’? means caverns. | 
voi No. 2. 8 
