Keystone Arch Bridge, Westfield River, Chester, Massachusetts Following the West Branch gave the railroad builders the lowest altitude crossing of the Berkshire Range. The serpentine course of the river made constant bridging necessary. Stonemason Alexander Birnie of Stockbridge was brought in to construct 27 bridges, culverts and walls in the mountain section of the line. Most impressive of these edifices were ten keystone arch bridges over the winding Westfield.
Helictites "A typical calcite helictite is a twisted, long cylindrical structure with a fine central capillary of about 0.2 - 0.35 mm diameter. Side micro-canals (``canalicules'') result in a somewhat porous structure. Typically the helictite has radial symmetry." from: http://www.speleonics.com.au/jills/pastpapers/helicat/