S\2 Dr Webster’s Account of the Hot-Spr'mgs (f Furnas 
mined by my friend Dr Dana, who found it fusible into a 
perfectly transparent glass^ when mixed with an alkali, and that 
six grains of it, in fine powder intensely [ignited in a platina 
crucible for fifteen minutes, lost 0.98125 grains, equal to 16.35 
per centT It appears from Dr Dana’s analysis, to consist of 
silex 83.65; water 16.35. It thus differs from the siliceous 
depositions of Iceland and Ischia, in the large proportion of 
water it contains, and in the absence of alumina and lime. It 
may be considered an hydrate of silex with more propriety 
than the hyalite of Frankfort, which M. Bucholz regards as 
such, and which contains but 6.33 of water It appears to be 
a new variety of siliceous sinter, and deserves to be designated 
by an appropriate name. From the island in which it occurs, 
I propose to call it Michaelite. 
Wherever cavities exist in the large masses of sinter, and in 
the hills formed by that substance, and the fragments of lava 
and pumice, the silex has assumed a stalactitic form ; and the 
stalactites are from one ta two inches in length, and their sur- 
faces are often covered with small brilliant crystals of quartz. 
It is impossible to convey any adequate idea of the beauty and 
variety of forms under which silex appears in St Michael, and 
mineralogists can here be supplied with specimens far surpas- 
sing those from any other localities as yet described. 
Another variety of stalactite that occurs here is composed 
principally of alumina. These stalactites are rough and earthy, 
and their length is from one to six inches. 
The more compact masses of sinter broken idown by the 
weather, and other causes, have been cemented together, with 
portions of obsidian, pumice, and scoriae, into very beautiful 
breccia, which is in some places sufficiently hard to admit a 
good polish. The cement is siliceous sinter. The difierent 
substances of which this mass is composed, exhibit a great va- 
riety of colour, and the fractured surface is curiously mottled 
.with green, red, grey, white, yellow, and black, in every variety 
of shade. Some of the portions have external characters analo- 
gous to those of wax-opal, and many are striped and spotted, 
• Klaproth analysed a quartzose concretion from the Isle of France, which 
contained per cewf. of water., 
