Everything in nature is expanded or increased in bulk by heat. You may see in a thermometer how the quick-silver or the coloured spirit rises in the tube, because it expands when the instrument is in a warm place, and how it sinks in a cold place. It is just the same with solids and gases. This would seem to be a universal law of nature, if it were not for the _single_ exception of water at the moment of its freezing. If water is cooled down to the freezing point, it will gradually diminish in bulk, but at the moment it turns into ice, it seems to spring outward, and increases considerably. In this way bottles are broken when the water in them freezes; and rocks are often split open in the same manner when the cracks in them contain water. You have seen that ice does not sink in water, but floats upon the surface; this takes place, because from the circumstance which I have told you, a certain quantity of ice by weight, occupies more space than the same quantity of water. Now it is worth while for you to see how wisely this is arranged, as it respects our own climate and country; for if ice were to sink to the bottom, the lakes, and rivers, and ponds, would become solid masses of ice during winter, which the sun's rays would never thoroughly thaw in summer, because, after the surface had been thawed, the rays would have to pass through the water to get at the ice at the bottom, and thus our climate would be rendered very much colder than it is at present, and perhaps the springs would not circulate, so that we should often suffer from scarcity of water. But when the salt water freezes, the ice is very porous, almost like a honeycomb, so that it is much lighter than frozen fresh water, and is very buoyant upon the sea, and stands out boldly to a great height, as is represented in the cut of the Icebergs. I will tell you of a perilous situation in which I was placed in my younger days, when I went a voyage to Greenland in a whale ship. It was at the end of the fishing season, and our ship was the last but one of the oil traders left in those seas; we had been very unsuccessful, having only taken five small whales, and we were anxious to amend our ill luck by tarrying after all the other ships had sailed, in hopes of better success. We were gently sailing about in search of whales amidst the broken ice when there suddenly arose a rather brisk breeze, at which time our ship was situated between two icebergs,--one of them very high and resembling a lofty mountain, and the other considerably smaller. Well, at the time the breeze sprung up, the large iceberg was to the windward of us, that is, on that side from whence the wind blew, and having a very large surface which caught the wind, it came sailing towards us very fast.