S/a/adi/fs ami Stalagmites. 29 



volume from blow-holes on the edge of the active pit. Carbonic acid, which is common 

 where volcanoes break through calcareous substrata, as in France and Italj^, is rare 

 on Hawaii ; so is chlorine and its compound with hydrogen, ( HCl ) h3'drochloric acid: 

 which would seem to show that sea-water does not often break through the island walls 

 to the molten interior. 



Minerals are uncommon in and around the Hawaiian volcanoes, but salts formed 

 by the union of escaping gase.^ with the elements in the lava are common as incrusta- 

 tions in the crater caves or under the crust of the floor, such as gypsum, alum, glauber 

 salt, etc. Augite in fine crystals, olivine in nodules of some size, mica in minute 

 hexagonal plates, quartz in small crystals, and rarely en >i/asse, are the more common 

 minerals. The gases convert the rocks into soil far more rapidly than the frosts 

 of colder climates. The sulphides of iron, pyrite and marcasite which have been 

 considered the source of the sulphurous vapors abounding in the crater when active, 

 must be almost entirely' decomposed for they are seldom found in the cold lava: natives 

 have brought me the former in small specimens thinking it gold, but I have myself 

 onl}' once found it in Kilauea. The ferrous oxides are common, both red and yellow, 

 and were well known to the old Hawaiians as a source of paint for their canoes, and 

 coloring for their kapas. They are often found in the lava streams as lumps or rounded 

 masses as if rolled, seldom as deposits, except in swamps as limonite. 



Stalactites and Stalagmites. — There is a curious formation, at times com- 

 mon in the caves that exist beneath the floor of Kilauea crater, and not infrequent in 

 similar caves in dead streams of lava on the mountain slopes. At first glance the 

 small grey rods that hang from the roof, and the curiously modeled droppings beneath 

 these, seem to be of igneous origin, or droppings of melted lava from the roof. An 

 examination /;/ s/t/i shows that this is not the case. The roof of these caves averages 

 two feet thick, and where the stalactites occur is unbroken. On removing the tubes 

 with care one finds no visible crack, and there is generally no fresh molten lava on the 

 upper surface. The formative process may be clearly seen as the tubes grow from 

 da}' to daj'. Professor Dana, after quoting my account in his "Characteristics of 

 Volcanoes," " could hardly believe the rapidit^^of the process, but observations repeated 

 more than once during the last fort}' years onl}' confirm my early description, which 

 I here repeat. I have caught the steel-grey deposit in the drops on the end of the 

 tubes upon my finger and watched its solidification. Usually the tubes are straight 

 cj-linders, from one to three-eighths of an inch in diameter, and somtimes more than 

 two feet long. As an}- sharp earthquake would at once break such long rods from the 



"Dana, Characteristics of Volcanoes, p. 341. 



[407] 



