52 HEAT OR CALORIC. 



(c.) The raising of pavements, and of the surface of the ground, 

 like a honey comb, thus breaking and preparing it, so that the veget- 

 able fibres can penetrate it. 



(d.) The throwing down, or distortion of stone walls, in moist land. 



(e.) The cracking of timber, and even of rocks, sometimes with 

 explosion, in very cold countries. 



(f.) The bursting of closed cannon and bomb shells, when water 

 is congealed in them. 



Huygens burst an old cannon, and Major Williams burst bomb- 

 shells at Quebec. In one of his experiments, " an iron plug, 2 f 

 pounds weight, was projected from a bomb-shell, to the distance of 

 four hundred and seventy five feet, with a velocity of more than 

 twenty feet in a second." 



(g.) Water, being confined by means of a moveable plug or stop- 

 per, in a strong brass tube, three inches in diameter, raised seventy- 

 four pounds, when it froze. Boyle. 



(h.) The Florentine academicians burst a hollow brass ball, one 

 inch in diameter, by freezing the water with which it was filled. 

 Muschenbroeck. calculating from the tenacity of brass, and the thick- 

 ness of the ball, inferred, that the expansive force was equal to twen- 

 ty seven thousand seven hundred and twenty pounds. 



12. But for the inequality of water in contracting, just before its 

 congelation, the globe would not be long habitable. 



(a.) There are both ascending and descending currents in water, 

 while cooling or heating. 



(5.) In the case of cooling water, these currents, while unobstruct- 

 ed, tend to cool it equally. 



(c.) In consequence of the exception that has been stated, they 

 are arrested at 40, and then the surface water does not descend any 

 more. 



(d.) It remains, is cooled, and freezes, and the ice, being a bad 

 conductor of heat, greatly retards the freezing of the water below. 



(e.) Thus only a few inches, or at most feet of ice are formed, 

 and the next summer is sufficient to thaw it. 



(/.) Were it not for this peculiarity, the deep rivers and lakes in 

 cold latitudes would freeze to the bottom, and therefore would never 

 thaw again, as the summer would not be long enough for that pur- 

 pose. 



(g.) The process would, every winter, advance farther and farther 

 towards the equator, and ultimately the ocean would freeze as solid 

 as stone. 



(h.) Thus, animal and vegetable life would be finally extinguished. 



(i.) All this mischief is prevented by this, apparently, trifling and 

 really solitary exception, evidently instituted on purpose by the Cre- 

 ator, one of whose characteristics it is, to effect the greatest results 

 by the smallest means. 



