208 HAWAIIAN ISLANDS. 
Silica and undecomposed silicate of alumina, - - - 71:170 
Carbonate of lime, : 2 é 4 z 2 : - 17:168 
Water, -— - - os = ae oa ae 8196 
Alumina and oxyd of iron, - 2 = 6 5 é SP elet70 
Magnesia, - : = 5 : i : L , 0°175 
Soda, - : - 4 = : Z é : Bee ONT 
Potash, - - - - - “ C : 2 7 0:115 
He remarks that the mineral is probably a mechanical mixture, 
consisting principally of carbonate of lime and a hydrous silicate of 
alumina; the latter is related to the Halloysite group of minerals. 
Specific gravity 2-024. Hardness, 4.5—5. Structure, compact mam- 
millary, and somewhat concentric lamellar. Colour, white to gray. 
Lustre, purely vitreous. When breathed on, gives a peculiar bitter 
odour, which is very evident when the mineral is ground beneath 
water in an agate mortar. It is allied to concretions from Samoa, © 
described in the chapter on that group of islands. 
But little is known with regard to the eruptions of the summit 
crater. Yet there is abundant evidence that, even at the present time, 
its fires are not entirely inactive. 
An eruption is stated to have taken place on the 20th of June, 1832, 
and the mountain continued burning for two or three weeks; the 
lavas broke out in different places, and were discharged from so many 
vents, that the fires were seen on every side of the dome, and were 
visible as far as Lahaina, upwards of one hundred miles.* 
The first ascent to the summit of Mount Loa by a foreigner was 
made by Mr. Douglas. ‘This author describes it as far surpassing 
Kilauea in sublimity and violent activity. Mr. Douglas’s observa- 
tions are, however, received with incredulity by the residents. ‘The 
residue of silica remained after digestion in hydrochloric or nitric acid, and the mineral 
did not gelatinize even by prolonged and warm digestion. The inference from this exa- 
mination was, that the mineral was a mechanical mixture of carbonate of lime in variable 
proportions with a silicate of alumina, and that no constant constitution could be assigned 
to it. The digestion of several distinct samples to complete exhaustion in strong acids, 
yielded the very variable results of 76°18, 63°72, 68°17 per centum of silica or undecom- 
posed silicate of alumina. The amount of carbonic acid determined by the balance was 
9°15 per cent. = 17-65 per cent. of carbonate of lime, while the analysis yielded 17°168. 
The water in this specimen varied from 7°68 to 8°196 per cent. in different trials.” 
* American Journal of Science and Arts, xxv. 201, in a communication from Rey. J. 
Goodrich, dated Nov. 17, 1832. 
