PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 605 



In order to fully ap|)rcciato the power of these molecular forces, it is only 

 necessary to refer to Dr. Tindall's admirable work on " Heat as a Mode of 

 Motion," After calculating the mechanical value of the energ-y developed 

 when the atoms of one pound of hydrogen and eight pounds of oxygen 

 attract each (.)ther, fall and clash together, when the molecules of steam 

 thus generated condense to water, and this water is converted to ice, the 

 author says: 



" Thus our nine pounds of water, in its origin and progress, falls down 

 three precipices. The first fall is equivalent to the descent of a ton weight, 

 urged by gravity down a precipice 22,320 feet high; the second fall is 

 equal to that of a ton down a precipice 2,900 feet high; and the third is 

 equal to a descent of a ton down a precipice 433 feet high. 



" I have seen the wild avalanches of the Alps which smoke and thunder 

 down the deelivities with a vehemence almost sufficient to stun the observer. 

 I have also seen snow flakes descending so softly as not to hurt the fiagile 

 spangles of which they were composed, Ye-t to produce from aqueous 

 vapor a quantity of that tender material which a child could cany, de- 

 mands an exertion of energy competent to gather up the shattered blocks 

 of the largest avalanche I have ever seen, and pitch them to twice the 

 height from which they fell." 



Such is the impressive estimate of the force expended in the formation 

 of a pound of ice from its component elements in the gaseous state; yet it 

 will be observed, by the figures already presented, that the energy devel- 

 oped in one nocturnal display' of the Highland beacon was sufficient to have 

 thrown the fragments of five such avalanches to the same height. 



Thoreau, the student and lover of nature in her wild moods and original 

 garb, doubtless, with Mingled feelings of awe and delight, beheld from 

 that beacon tower the surging of the sea, ^nd heard, in sullen sounds, the 

 threatenings of a tremendous force; but as he turned toward the light, 

 which fixed the gaze of many an anxious mariner, he did not realize the 

 truth that art had there trained nature to perform the conmion service, 

 which must ever be regarded as one of her greatest miracles; and that, to 

 guide the sailor along the dangerous coast, she sent forth her messengers 

 of light amid the ambient £eth, whose undulations, in each and every minute 

 of time, outnumber all the ocean waves that have culminated since man 

 first ventured on the deep. 



On motion the Association adjourned. 



