/Fucus/ and /Laminaria/ constitute the kelp from which iodine is obtained, and were at one time the source of the potash of commerce. /Fucus vesiculosus/ is a constituent of a medicine used as a cure for obesity. /Chondrus crispus/, commonly known as Irish moss, was a few years ago generally used as an article of diet. /Porphyra vulgaris/ (laver) is used by the Chinese for soups. /Rhodymenia palmata/ (dulse) is an article of food in Ireland and Scotland. [pg039] /Gracilaria spinosa/ is used by birds, allied to the swallows, for making their nests—the edible nests found in large numbers on the islands of the Indian Archipelago, especially in the caves on the shores of Java, and gathered and sent to China, where they bring large prices and are used in making the famous birds'-nest soup. /Gracilaria lichenoides/, also a species of the Eastern seas, is the source of agar-agar, a preparation used in laboratories as a culture-medium for bacteria. Fossil diatoms are ground and used for polishing-powders. Seaweeds are everywhere used by farmers on the coasts as fertilizers. [pg040] XI COLLECTING AT BAR HARBOR The beautiful coast of Maine is a particularly good field for shore-collecting. The rocky coast harbors the boreal fauna and flora which depend upon such physical conditions, and the shores at Bar Harbor are typical of those found elsewhere in northern New England. The rocks give shelter from the beating surf, while life has exposure to the cold, pure waters of the arctic current. Everywhere along the shore, rock pools are to be found. These are perhaps the most fascinating of all spots to the collector. They are veritable gardens of the sea, where species flourish which naturally belong to deeper water, but which find in such pools conditions suitable to their existence. At Bar Harbor one well-known and frequently visited rock pool is found in Anemone Cave. Entering a field at Schooner Head, one turns to the right and follows the rocky shore for two or three hundred feet. It is difficult to take this short walk without being constantly diverted and delayed by the various attractions one meets, such as the tide-pools, the barnacles which in places whiten the rocks, the periwinkles, the purpura shells, and the curious algæ; but at last one arrives at a cavern under an overhanging rock. Here is a large tide-pool which at first sight displays only a beautiful scheme of color. It is carpeted with a bright-pink alga, /Hildenbrandtia rosea/, which incrusts the basin of the pool.