V. On hollow pyramidal ice crystals

• Published in: Proceedings of the Royal Society of London
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1894
• Subjects: Recess; Iceland
• Online Access: http://dx.doi.org/10.1098/rspl.1894.0020; https://royalsocietypublishing.org/doi/pdf/10.1098/rspl.1894.0020

I. The Lava Cavern, Surtshellir .—At a visit to the lava cavern, Surtshellir (Iceland), in June, 1892, the farthest recess, which contains ice stalactites and an ice pond, was found to be covered on walls and ceiling with ice crystals in the form of hollow hexagonal pyramids, analogous in shape to the well-known cubic crystals of rock salt. The hollow ice pyramids were, roughly speaking, built in the proportion of base 1 to height 2, and ranged up to about 1 in. diameter of base. They were attached to the wall by their apices, turning their hollow bases towards the interior of the cave. They were only found on those parts where stalactites did not occur. The temperature was +0.5° C. (+33° F.), and, as the cave forms a cul-de-sac , the air is perfectly calm. The crystals, having thus evidentia been formed from the moisture of the atmosphere, had to be considered as a kind of hour frost.