that occur perforating Sheets of melting Ice. 307 



through the ice. In the bottoms of these, I always observed 

 solid bodies — stones, dust, sand, bark of trees, or the like. 

 In one instance, of which I had taken particular notice, I 

 subsequently observed that the imperfect hole had been ren- 

 dered complete, and corresponded in size to those, the cause 

 of whose formation I had been attempting to discover. I 

 then placed a stone above a piece of ice during sunshine, and 

 examined it on the following day, when a complete hole, 

 bigger than the stone, was found in the ice below the place 

 where it had rested. I confirmed these observations by ex- 

 periments repeated under varied circumstances, always with 

 like results. Thus, having placed upon ice almost all such 

 small bodies as are usually found on the sides of rivers, I ex- 

 posed it, in order to melt, both in the rays of the sun and in a 

 warm atmosphere. In all the experiments, holes were pro- 

 duced. I have also seen, where two sheets of melting ice were 

 lying, one above the other, a complete hole through the upper, 

 and an incomplete one through the under sheet, continuing 

 the upper hole, and having at the bottom a bit of clay. Under 

 the same circumstances of temperature, holes were produced 

 when the bodies were put below the ice, so as to allow it to 

 rest on them; and when dust, crumbs of brown wood, and 

 other such light substances, were placed below, they rose up, 

 by capillary attraction, as the holes upwards approached the 

 surface, always keeping the top of it, till the holes were com- 

 pleted. After exposure for one or two days, the holes pro- 

 duced in my experiments, as also those whose formation I had 

 watched, were, by continued melting, ultimately smoothed 

 into the same appearance as those for whose origin I had been 

 seeking to account. 



The principle on which these foreign bodies act in pro- 

 ducing holes, is their possessing the property of absorbing ra- 

 diated heat in a higher degree than ice. That this explana- 

 tion may be applicable to cases in which the body has sunk so 

 far into the ice as to be out of the reach of the direct rays of 

 the sun, or has been originally below the ice, it is necessary 

 that ice should give passage to the heat of the sun's rays. 

 That ice has this property, was determined experimentally. I 

 took a sheet of pretty-transparent newly frozen ice, fully half 

 an inch thick, and having smoothed the inequalities of its sur- 

 faces, I found that I could inflame a piece of sealing-wax, by 

 concentrating on it the rays of the sun, by means of a burning- 

 glass, whether the ice was interposed between the sun and the 

 lens, or between the lens and the wax. The effect, indeed, 

 seemed to be little diminished by the interposition of the ice. 

 Yet, that ice does not transmit heat altogether without inter- 



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