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XLV. On the Cause of the Holes that occur perforating 

 sheets of Melting Ice. A Prize Essay in the Chemical ClasSy 

 Marischal College, Aberdeen, Session 1887-8. By John 

 Ferguson, qfNigg, Student of Medicine'^. 



npHE holes in question are generally about one or two 

 -*- inches, and sometimes more, in diameter. In shape, 

 they are more or less round, but seldom completely cylin- 

 drical. In direction, they are most commonly perpendicular 

 to the surface of the ice. After a thaw, they may be readily 

 seen in the sheets of melting ice that float down a river, or on 

 the sea-shore near its mouth. They occur not only in very 

 thin sheets of ice, but in ice upwards of three inches in thick- 

 ness; and not only in ice disintegrated by melting into a po- 

 rous texture, but in ice apparently the most compact. 



In order to ascertain the cause of these holes, the structure 

 of ice was first considered. Depressions, especially in the 

 under surface of ice, may be observed, and, at such depres- 

 sions, it may be supposed that the ice will melt into holes ; ; 

 and this in fact happens. But the holes thus formed are seen, 

 only in ice less than half an inch in thickness, they are bound-, 

 ed by thin sharp edges, and they are seldom round, so that- 

 they do not at all resemble those that are the object of the, 

 present inquiry. 



Air cells, which are to be found in all ice, varying greatly, 

 in their size and frequency in different pieces, but in both re- 

 spects very equally distributed in the same piece, may also 

 produce small holes in very thin ice ; but these are easily di- 

 stinguished from the larger holes in question, which, as has al- 

 ready been mentioned, occur in ice, although thick, and whe- 

 tlier porous or compact. 



, Ice, in freezing, has a tendency to assume a crystalline 

 structure, which, were it to differ in any one part from the 

 rest, might, in such part, occasion a corresponding facility in 

 the melting. Yet no such difference was detected by inspect- 

 ing newly frozen ice; and pure newly frozen ice was observed 

 to melt by a warmer atmosphere, or by the sun, without form- 

 ing any of the holes in question. Ice, indeed, while melting, 

 sometimes appears to consist of a number of prisms laid loosely 

 in apposition, and directed perpendicularly to the plane of 

 the sheet. But I could never succeed in driving any one of 

 these prisms through into a hole, without, at the same time, 

 breaking the surrounding ice. Besides, the holes to be ex- 

 plained are not peculiar to ice of such structure. 



• Communicated by Professor Clark of Aberdeen. 

 Fhil, Ma<r. S. 3. Vol. 15. No. 96. Oct. 1839. X 



