FKOZEN WELL. 203 



Why might not the same effects be produced in a porous soil above a frozen mass? 

 That evaporation does take place to a considerable depth, even in common soil, is mani- 

 fest during a drought ; and in a gravelly soil it must occur still deeper and more abund- 

 ant. Is it strange that such a cause, acting with the influence of a non-conducting deposit 

 of clay, should effectually protect a frozen mass like that at Brandon, through thousands 

 of years, ever since the modified drift period, from external heat? 



But however we may explain it, the frozen earth of high northern localities has not been 

 melted by internal heat since a period even anterior to that of drift, though the fact that below 

 a certain point the heat increases even in the frozen mass, shows, in our opinion, that some 

 effect comes from this source ; yet so slight is it, that the soil remains frozen to this day to 

 an immense depth. And we have the opinion of one of the most distinguished of the 

 European geologists, Sir Henry de la Beche, that ice might have been preserved in such 

 circumstances from the drift period to the present day. " Descended to a certain depth, 

 beneath the surface," he says, "but not sufficient to bring it within the influence of the heat 

 found to exist beneath certain depths in different parts of the globe, ice might remain 

 there only to be thawed by a great increase in the temperature of the general climate, or 

 by being again elevated, with a sufficient denudation of protecting detritus so that the 

 heat of the atmosphere in summer would dissolve it and disclose any animal remains 

 which may have been there imprisoned." Geological Observer, p. 293. Why may not the 

 same reasoning be applied to Vermont as well as to Siberia ? 



The decided influence of the temperature of the atmosphere at the earth's surface upon 

 frozen wells, may seem at first thought sufficient to account for their condition, without 

 supposing a remnant of the ice of the drift period in their vicinity. The fact that the 

 temperature of the wells is greatly affected by the external air is unquestioned ; for the 

 ice accumulates in them during the winter, and usually all thaws out before the close of 

 summer. We have endeavored to show how the circulation of air through porous strata 

 would produce such an effect. As winter approaches, the cold and heavy air would grad- 

 ually work its way into the soil, and gradually lower the higher temperature beneath the 

 surface. But would it ever be lowered below the freezing point, if there were not a cold 

 mass below the surface with which it might come in contact ? Then why are not all wells 

 in porous soil converted into frozen ones ? The fact that so few of them are such, gives 

 plausibility to the idea that it needs a frozen nucleus to help on the process of freezing in 

 winter, and retard melting in summer. 



But, though we think this the most probable view of the subject, yet is it not possible 

 to imagine a conjunction of circumstances in which frost may be produced deep in porous 

 strata, and be gradually accumulated ? Suppose layers of non-conducting materials to 

 be underlaid by strata of coarser fragments, so situated at the extremities as to make the 

 egress and ingress of air easy, either by simple difference of specific gravity, or aided 

 perhaps by the pressure of wind. Suppose more or less of water to percolate through the 

 gravel, and might not the evaporation by the air currents be sufficient in the winter to 

 produce congelation deep beneath the surface, along the line of the currents ? Might not 

 a winter unusually long and cold produce so much of frost that the subsequent summer, 

 especially if short and cold, would not melt the whole ? And might not there happen a 

 succession of such cold winters and summers, so as to accumulate a considerable quantity 



