OF ARTS AND SCIENCES: FEBRUARY 11, 1873. 507 



Professor J. M. Crafts read a paper on " The Volumetric 

 Analysis of Iron Ore." 



Professor E. N. Horsford read a communication on " The 

 Columnar Structure of Ice." 



Dr. Charles Pickering continued his remarks, made at a 

 previous meeting, on the forming of the earth's crust as wit- 

 nessed in a congealing lava-lake within the great crater on 

 Hawaii : — 



On the floor of this and of the terminal crater of Mauna Roa (both 

 of which on crossing he found essentially alike), sulphur occurs in the 

 form of invisible fumes, impeding respiration, and in little heaps of 

 comminuted dry powder ; while above, around the brink, the sulphur 

 comes through steam-vents forming regular " fumaroles," and is all 

 beautifully crystallized ; water in the one instance being accessible, in 

 the other not. 



Might not the similar little heaps of dry, white, tasteless powder on 

 the floor of these craters have become some familiar mineral, could 

 they have obtained water of crystallization ? 



The only crystalline mineral he could discover in the Hawaiian lavas 

 was chrysolite, pea-like, and, though nowhere abundant, universally dif- 

 fused ; in some instances attached to a thread of the capillary obsidian, 

 and therefore already formed when it reached the atmosphere ; more 

 frequently embedded in solid lava, a foot, perhaps, from atmospheric 

 contact. Chrysolite occurs also in the neighboring Mauna Kea con- 

 glomerate, but in little patches, and not in detached crystals ; and espe- 

 cially deserves attention from its presence in meteorites recently an- 

 nounced, presenting unexpected analogy with the internal constituents 

 of our own planet. 



When the accumulation of liquid lava becomes so great that the walls 

 of the crater give way, a portion is sometimes squeezed through cracks 

 a thousand feet upward upon the very brink. From the great crater 

 the escaping lava splits the rock before it on its way down to the sea, 

 in some instances leaving behind a squeezed-up portion here and there 

 upon its track. 



In the eruption a few months before his visit, the lava, after thirty 

 miles' progress in the above-described manner, coming out upon the 

 surface, poured into the sea. The consequence was a sand-storm, un- 

 approachable for some days. When this cleared up, the new lava was 



