66 Transactions of the American Institute. 



which must be borrowed from the surrounding substances. In the 

 vessel of water he immersed two thermometers, one near the top and 

 the other near the bottom. As the temperature of the water fell, the 

 lower thermometer descended to 39|- deg., and there remained 

 stationary, while the upper thermometer continued to fall, and at 

 last reached the freezing point. Why does not that system of currents 

 keep going on like the boiling of water in a flask, so that the whole 

 shall ft'eeze at the same time ? • That is just where this wonderful 

 exception takes place, and it is the great delight of a devoted mind 

 to believe that the exception is a part of the original intention of the 

 Great Architect in the formation of the world in adapting it to be 

 inhabited by human beings, because we may readily believe that, 

 except for this irregularity in the exception of water the world would 

 be uninhabitable. At the temperature of 39|- degrees the very con- 

 trary effect takes place, and the water begins to expand, it increases 

 in bulk, and consequently becomes specifically lighter, and, like a 

 cork, floats upon the surface, or immediately beneath it ; so that 

 you will have the surface of the water cooled down to 32 degrees, and 

 converted into ice, and yet that freezing does not extend much below 

 the surface. You rarely find, in the coldest winter, that ice is formed 

 more than two feet thick. If you observe a caldron of molten iron as 

 it cools does it solidify first on tlie top ? No. Does a mass of lead in 

 a ladle solidify at the top ? No ; but equally at the bottom. In 

 most cases the solid, which is the result of congealation, is heavier 

 than the fluid in which it is formed and sinks to the bottom, wherein 

 in the case of the water the solid is much lighter than water. 

 We have here another exception that the ice which is formed 

 is lighter than the water and it floats upon it. When we see 

 an iceberg from 100 to 200 feet above the surface of the sea we 

 know that for every foot of elevation above water there are ten 

 feet of depression beneath the surface; so that what we see is 

 only one-eleventh of the whole bulk. Lake Superior has a uni- 

 form temperature of about forty degrees, and beneath the surface, in tlie 

 winter, in an}^ of our lakes we shall find water at about that tempera- 

 ture. This is an important fact with reference to the inhabitability 

 of our globe ; because, you observe, that if water as it solidified con- 

 tinued to shrink and to become heavier, the whole mass would 

 become frozen in a single winter so that no summer would be long 

 enough to melt it, and eternal death would rest upon the surface of 

 the globe. [In the freezing mixture Professor Silliman inserted one 



