458 E. 8. Dana — Petrography of the Sandwich Islands. 



diameter and sometimes more than two feet long. The bore is 

 almost never continuous, and while externally they are smooth, 

 within a mass of stony cells of considerable size is presented. As 

 long as these tubes grow downward in the quiet upper region of 

 the cave they hang perpendicularly, but when they reach farther 

 down the currents of air and steam blow the deposits to one side 

 and the tube becomes distorted ; it may even return on itself. 

 The drip in the bottom forms much thicker and more irregular 

 stalagmites as will be seen from the figure which represents three 

 actual forms not occurring, however, in the same cave. Speci- 

 mens have been found which exceed eight inches in diameter and 

 these are usually low and flat topped. The more slender ones 

 sometimes rise to a height of two feet ; and so rapidly is the 

 silica deposited that they seldom increase in diameter but are 

 true acrogens, none of the suspended silica running down the 

 sides. In one cave the growth of the stalactites was at about the 

 rate of an inch a week but owing to the varying amount of water 

 or steam the production is quite irregular. They are often 

 coated with beautiful white crystals of gypsum, sometimes tipped 

 with needle-like transparent crystals of the same mineral when 

 the cave is high. The natives collect them with the upper open 

 joint of a long bambu." 



The following analysis of the solid stalactite, by John C. 

 Jackson, is given by Brigham : 



Si0 2 A1,0 3 Fe 2 3 MnO CaO MgO Na 2 K 2 

 G. = 2-9 51-9 13-4 15-5 0"8 9"6 4-8 3-0 1\L = 100'1 



3. Lavas of Kilauea. 



The specimens in hand from the volcano of Kilauea, which 

 have been examined microscopically, include four specimens 

 (12, 16, 17, 18) of the recent lava from the bottom of the 

 crater, six specimens of the older lavas, two (13, 15) from 

 Waldron's ledge on the northeast side and four (14, 19, 20, 26) 

 from the wall west of Halemaumau ; finally a number (1-11) 

 from the ejected masses on the borders of the crater, especially 

 on the west side. There are also a number of glassy and 

 scoriaceous kinds. 



1. The recent lavas. — The specimens of the recent lavas 

 were taken from the stony part of the layer below the inch or 

 more of glassy crust. They are dark colored, vesicular basalts, 

 containing chrysolite but not in very large amount. The 

 irregular grains of chrysolite are often aggregated together 

 with augite crystals and to a limited extent with the lath- 

 shaped feldspars, these constituents obviously representing 

 those which first separated from the magma. The mass of the 

 solid portion of the rock is of uniform character, consisting of 

 augite and feldspar with the interstices between them black 

 with the crowded grains or plates of magnetic and titanic iron ; 



