336 Dr. LeConte on a remarkable Exudation of he 



heat, but was resumed as soon as that influence was with- 

 drawn. The state of the soil was carefully examined ; for it 

 seemed to be almost certain, that the process of formation 

 must have been going on under the eye at the time the ob- 

 servations were made. The subjacent clay was found to be 

 moist and unfrozen, the icy columns separated from it with 

 the slightest touch, and 'were not connected with any formation 

 of ice below. As already intimated, in less favourable situa- 

 tions, when the frigorific action was intense, the soil on which 

 the columns rested sometimes became incrusted with ice, after 

 the protrusion had commenced ; but this was invariably at- 

 tended with a complete arrestation of the process : indeed, 

 under such circumstances, it was obvious that there had been 

 an imperfect development of the phaenomenon. In these 

 cases, a stratum of frozen earth was found adhering to the 

 bases of the columns, while continuous icy threads were ob- 

 served to transpierce this crust perpendicularly, and occasion- 

 ally to extend into minute apertures in the unfrozen soil be- 

 neath it. As already remarked, in more favourable situations 

 the ground beneath was never frozen ; but on cautiously re- 

 moving 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 position with the bundles 

 of thread-like ice, and which were frequently of sufficient size 

 to be quite obvious to the unassisted eye. 



Having thus described with sufficient fullness the phaeno- 

 mena attending the occurrence of exudations of icy fringes 

 from the stems of plants, as well as the protrusion of columns 

 of ice from certain soils, we are now prepared to offer some- 

 thing in explanation of them, and to attempt to rise from the 

 mass of details to the causes which have given birth to these 

 remarkable appearances. A careful examination and collation 

 of the two series of facts above recorded develope so many 

 strong points of analogy, that it is almost impossible to resist 

 the conviction, that both of the phaenomena must be referred 

 to the same cause. If we admit an identity of cause in the 

 two cases, it is obvious that it must be \inve\y physical \ since 

 that which relates to the production of the phaenomenon on 

 certain kinds of earth is necessarily physical. In the remarks 

 which follow, therefore, I shall treat the question as one of 

 physics, and shall apply them more particularly to the phae- 

 nomenon exhibited by the soil : their application to the case 

 of vegetables will be easy and obvious. 



1. It is very clear that we cannot look to the store of va- 

 pour in the general atmosphere for the origin of the icy co- 

 lumns. For not only are the appearances above described at 



