452 E. S. Dana — Petrography of the Sandwich Islands. 



distinctly except as some of the microlites are to be referred 

 to it. 



Another specimen was lithoidal in character and showed 

 throughout a distinct spherulitic structure. The nearly opaque 

 spherulitic ground-mass contained many light brown transparent 

 spherulites, and grains of chrysolite were scattered through as in 

 the other 



Lava streams from Maun a Loa. — A considerable number 

 of specimens are at hand from the streams of Mauna Loa of 

 different dates, and taken from points at various altitudes. 

 For the most part they are simply the surface scoriaceous por- 

 tions and consequently without distinctive features. The flows 

 of 1852, 1855-56, 1859 are thus represented. There are also 

 specimens of the normal crystallized lavas of the stream, 1881, 

 at Hilo ; of that of 1813 taken from near its source which has 

 been already alluded to, and of 1868, 1880-81, 1882 and 1887. 

 These are all dark colored chrysolitic lavas, vesicular in a high 

 degree, especially that from near Hilo (1881) and their charac- 

 ters are those of the vesicular forms spoken of on page 150. 

 The specimens of the flows of 186S are to be mentioned as 

 particularly rich in chrysolite. 



2. Lava Stalactites from caves in the Mt. Loa lava streams. 



Perhaps the most interesting and remarkable formations con- 

 nected with the lava flows from Mauna Loa are the delicate 

 stalactites and stalagmites of lava which ornament the caverns. 

 The specimens in the collection are mostly from a cavern in 

 the lava stream of 18S1, near Hilo, as described on page 109 of 

 the last volume of this Journal. Figures of some of the forms 

 of similar stalactites from the caverns of Kilauea are given by 

 Brigham as more particularly mentioned later. They are of so 

 great interest as to demand a minute description. 



According to the accounts given, the flowing lava stream, 

 crusted over at the surface, leaves behind it, when the molten 

 material has flowed by, long caverns usually eight or ten 

 feet in height, having a roof of one to three or more feet in 

 thickness and a floor of the solidified lava. In the caverns are 

 found hanging from the roof the slender lava stalactites. In 

 the Hilo cavern they were from a few inches to twenty or 

 thirty in length, and in some places only six to eight inches 

 apart. The diameter, which seems to have been determined 

 by the size of the drop of the liquid material, does not vary 

 much, being usually about a quarter of an inch. Beneath 

 the stalactites, from the floor below, rise the clustered groups 

 of the stalagmites. These delicate forms are so fragile that 

 they hardly bear transportation, and it is consequently diffi- 

 cult to preserve the longer specimens in their original form. 



