this subject seem to suggest it as a point of the inquiry to be made, whether the habitat of certain fish does not indicate the temperature of the water; and whether these cold and warm currents of the ocean do not constitute the great highway's through which migratory fishes travel from one region to another. Why should not fish be as much the creatures of climate as plants, or as birds and other animals of land, sea, and air? Indeed, we know that some kinds of fish are found only in certain climates. In other words, they live where the temperature of the water ranges between certain degrees.
159. A shoal of sea-nettles.—Navigators have often met with vast numbers of young sea-nettles (medusœ) drifting along with the Gulf Stream. They are known to constitute the principal food for the whale; but whither bound by this route has caused much curious speculation, for it is well known that the habits of the right whale are averse to the warm waters of this stream. An intelligent sea-captain informs me that, several years ago, in the Gulf Stream off the coast of Florida, he fell in with such a "school of young sea-nettles as had never before been heard of." The sea was covered with them for many leagues. He likened them, as they appeared on near inspection in the water, to acorns floating on a stream; but they were so thick as completely to cover the sea, giving it the appearance, in the distance, of a boundless meadow in the yellow leaf. He was bound to England, and was five or six days in sailing through them. In about sixty days afterwards, on his return, he fell in with the same school off the Western Islands, and here he was three or four days in passing them again. He recognized them as the same, for he had never before seen any like them; and on both occasions he frequently hauled up buckets full and examined them.
160. Food for whales.—Now the Western Islands is the great place of resort for whales; and at first there is something curious to us in the idea that the Gulf of Mexico is the harvest field, and the Gulf Stream the gleaner which collects the fruitage planted there, and conveys it thousands of miles off to the hungry whale at sea. But how perfectly in unison is it with the kind and providential care of that great and good Being that caters for the sparrow, and feeds the young ravens when they cry!
161. Piazzi Smyth's description.—Piazzi Smyth, the Astronomer Royal of Edinburgh, when bound to Teneriffe on his celebrated astronomical expedition of 1856, fell in with the annual harvest
