NATURAL PHILOSOPHY. 



159 



and they are more or less transparent, depending apparently on the 

 purity of the water and the state of aggregation of the icy filaments. 

 Sometimes the fibres are readily separated ; at others they are fvised 

 together. When examined by transmitted light, transverse stria; are 

 observed to cross the filaments at intervals of from one tenth to one 

 thirtieth of an inch. The columns vary in length from one to four or 

 even five inches, and in size from mere threads to prismatic bundles 

 of one fourth of an inch in diameter. 4. On examination the colunn.s 

 were found to terminate sharply at the surface of the earth, never 

 being connected with any formation of ice below where the phenome- 

 non was fully developed, and, in most cases, the soil from which they 

 protruded was not frozen in the slightest degree, even in the severest 

 weather, when the thermometer stood as low as 5. Though the 

 ground was not frozen, yet, on cautiously removing the icy columns, 

 the moist clay was found to present a very porous appearance, as if 

 perforated by a multitude of holes or spiracles, corresponding in posi- 

 tion with the bundles of thread-like ice. 



A careful examination of the two series of facts, with reference to 

 the exudations of icy fringes from the stems of plants and the protru- 

 sion of columns of ice from certain soils, must convince every one that 

 both of these phenomena should be referred to one and the same 

 cause. If we admit this identity of cause, it must obviously be a 

 purely physical one. The author then shews from various facts what 

 cannot be this cause, confining himself more particularly to the phe- 

 nomenon exhibited by the soil. Tt cannot be caused by the vapor in 

 the general atmosphere. Nor can it be occasioned by the cold con- 

 tracting a superficial stratum of earth, and thus forcing 1 up the mois- 

 ture which freezes at the surface. Nor, again, ran it be owing to the 

 exhalation of aqueous vapor from the comparatively warm earth be- 

 neath through spiracles, undergoing condensation and congelation at 

 the surface, and thus protruding the column. Neither can the pro- 

 trusion be ascribed to the mere exparsica of water during the act of 

 freezing in the capillary tubes of the clay. Though in the well-known 

 expansion which water undergoes before congelation commences, we 

 have a cause sufficiently universal and acting in the right direction, 

 yet calculation shows that it is entirely inadequate for the production 

 of the phenomenon. It being impossible for any of these to be the 

 causes of the phenomenon, Prof. Lc Conte offers the following as the 

 most probable explanation of it. Let r.s suppose a portion of tolera- 

 bly compact, porous, and warm earth, saturated with moisture, to be 

 exposed to the influence of a cold-producing cause. Only a very 

 superficial stratum of the soil would be reduced to the freezing point. 

 As the resistance to lateral expansion is less at the surface than it is 

 at a sensible depth below, the effect of the first freezing would be to 

 render the apices of the capillary tubes or pores conical or pyramidal. 

 The sudden congelation of the water filling the conical capillaries in 

 the superior stratum would produce a rapid and forcible expansion, 

 which, being resisted by the unyielding walls of the cone, would not 

 only protrude, but project or detach and throw cut the thread-like 

 columns of ice in the direction of least resistance, or perpendicular to 



