430 ACCOUNT OF THE ARCTIC REGIONS. 



which resemble white hair cut into lengths not ex- 

 ceeding a quarter of an inch, are so small and clear, 

 that the exact figure is not easily determined ; and 

 the larger exhibit a fibrous or prismatic structure. 

 Some of these are occasionally the third of an inch 

 in length. This genus is only seen when the tempera- 

 ture is near the freezing point. When the thermo- 

 meter is about 28 degrees, the finer specimens occur; 

 when about the freezing, the coarser appear. The 

 latter are very common during fog showers, and ap- 

 pear to be composed of aggregations of the frozen 

 particles of the fog, and to have their origin in the 

 lower parts of the atmosphere. 



4. Heocagonal pyramids. — This kind of snow- 

 crystal I have but once seen. A variety, consisting 

 apparently of a triangular pyramid, was observed ; 

 but whether its base was a triangular or six-sided 

 figure, similar to No. 96. Plate XI. is doubtful. 

 These pyramids were about the thirtieth part of an 

 inch in Iieight, and fell along with some other curi- 

 ous figures, during a fresh gale of wind from the 

 nortliward, in very large quantity. Figures 44, 

 and 47, Plate IX. represent this kind of crystal. 



5. Spiculos or prisms having one or both ex- 

 tremities inserted in the centre of a lamellar crys- 

 /«/.— This is the most singular genus I have ever 

 seen, and has been observed but twice. It re- 

 sembles a pair of wheels, united by an axletree ; the 

 wheels consisting of hexagonal or other lamellar crys- 



