On the side of physical factors this attempt took the form of crude magic, adjuration, sacrifice, and incantation, all of which were calculated to dispose the physical elements favorably toward the individual concerned in the ceremonials. Crude ritual observances and ceremonies, such as sacrifice, mimicry, and tableau, were believed to influence in some occult way the growth of crops, the changes in weather, the health of enemies, the movements of game, the supply of fish, etc. A typical fishing expedition among the natives of the Caroline Islands aptly illustrates this point of view. The chief official is not an expert boatman nor a fisher, but the medicine man of the tribe. He owes his authority not to his knowledge of the habits and haunts of fish, but to his store of incantations and exorcisms. Various rites are conducted before embarking. The fishermen must leave the island without speaking; and especially, the purpose of the expedition must not be mentioned aloud. A "luck" formula is pronounced over the boat. Sacrifices of special foods are offered, lest the lines be broken by sharks or tangled in the rocks. In Mexico, an elaborate pantomime, representing the harvesting of crops, was staged annually at a religious festival. This was believed sufficient to produce the good crops which were desired for the next season. Special dances were performed by persons representing the various vegetables which were particularly coveted. Among primitive races in almost every part of the world one finds magical properties attributed to a sort of toy which anthropologists call the "bull roarer." It consists merely of a flat stick, attached to the end of a cord. When whirled around it produces a roaring or humming sound which easily reminds one of the rumble of wind, the roll of thunder, or the distant cry of an animal. In various quarters this instrument is used in a ceremonial way. Since its sound resembles thunder, it is used as a charm against that form of physical violence. Because of its resemblance to both thunder and wind, it is incorporated in elaborate rain-making mysteries. Sometimes it is used to drive or call wild or domesticated animals, and hence comes to be used as a means of bringing luck to hunters. Figures and emblems, carved on the slab of wood, are supposed to specify the particular kind of luck or fortune which the individual seeks.