139 



Leslie {'^Eiwyclopcdia Britannica," vol, 3, art. Cold, 

 p. 258, Supplement) observed a protrusion of ice filaments, 

 like bundles of spun-glass, from a porous earthenware pan 

 into which he put water and which he maintained in the 

 presence of sulphuric acid in reduced air pressure. The 

 water was conveyed through the pores and crystallized out- 

 side in ice shoots, perpendicular to the surface of the 

 container. 



Le Conte ( 1852 ) obtained a similar effect by soaking ' ' the 

 smaller portions of soft and spongy roots ' ' of the cypress 

 in potassium nitrate and letting them dry in the air. 

 Crystalline fibers of the salt emanated at right angles to the 

 surface. The author compares these fibers to the filaments 

 of zinc sulphate which form at the surface of the earthen- 

 ware cups used in batteries. 



5. Tissues. Surface Freezing. The astronomer Her- 

 schel (the son of the famous William Herschel), in 1833, 

 observed, on some decaying thistles and on the stumps of 

 living heliotropes, ice ribands with a fibrous structure, a 

 silky surface and a frilled wavy shape (Fig. 12). The 

 ribands were formed longitudinally on the stem and per- 



FlG. 12. Foiniatidii of iee rilibons on plant stvinips. (From Horscliel, 

 1833.) 



