170 HAWAIIAN ISLANDS. 
dome: but the slopes spread very much below, diminishing to a single 
degree, so that the whole region of volcanic action subordinate to 
Mount Loa, is about seventy miles in width, or includes the entire 
breadth of the island, from east to west. The main part of the moun- 
tain, if considered a portion of a great sphere,* will correspond to a 
segment 13,760 fect deep, cut from a globe four hundred miles in 
diameter; or in form, to a segment about one-twelfth of an inch 
deep from a globe twelve inches in diameter: and in such a segment 
as last referred to, the terminal crater would be represented by an in- 
dentation one-fifteenth of an inch broad, and Kilauea by another one- 
tenth of an inch broad ; and both about a fifteenth of their breadth in 
depth. The dome, consequently, instead of having slender walls at 
top, has a horizontal thickness of full twenty miles eighteen hundred 
feet vertically below its summit.t 
The slope from Kilauea to the east coast at Nanawale, (the scene 
of the late eruption), averages but 1° 28’, or one hundred and thirty- 
five feet to the mile; it constitutes an extension of the base of the 
mountain in that direction. The southern point forms another exam- 
ple of the same kind, though of less extent. 
The declivities of Mount Loa have been described as covered with 
black patches of lava from the sea to the very summit, which, in most 
parts, are still bare, or but sparsely covered with vegetation. These 
patches are a result of distinct eruptions, and they show that lavas 
have found their way out, not only from the large vents, which are 
* It varies a little from a segment of a sphere, the upper parts being slightly more 
prominent. 
} For comparison with other lofty volcanic mountains we here mention a few other 
inclinations, as determined in different instances. 
The Peak of Teneriffe has an average inclination of 12° 30’, the proportion of height 
to diameter being given as 1 to 9. 
Etna, according to Elie de Beaumont, has an average inclination of 8 degrees, M. 
von Buch makes the ratio of height to circumference as 1 to 34, giving the angle 103 
degrees. ‘The Chimborazo dome, according to Humboldt, is only 673 toises through at 
a level of 153 toises (or 978 feet) below the centre of the top. 
It is much to be regretted that artists, when sketching mountains, are not content with 
giving them their actual slopes instead of attempting improvements by straightening up 
their sides, and sharpening their summits. Even in works of science, the same errors 
are common. We never see a drawing of Jorullo, which does not give the peak actually 
impossible slopes, taking Humboldt’s own facts as a criterion. Drawings of Vesuvius 
and Etna, in the most prominent of our geological treatises, are equally objectionable. 
A simple outline, if correct, gives reliable information ; and is far more valuable to science, 
than one improved to suit the fancy, though sketched with the skill of a master. 
