| Show detecting I 1 lair law wo in metal to detect hidden cracks opening froin from the stir surface face of metals the surface la is first firs I 1 moistened with kerosene and is then dried off with a cloth it is tl en coated with chalk after a little while the oil u works out of the little cracks and stains the chalk A sort of diagram of the hid den fissures and defects is thus pro deuced professor C lloyd morgan has in his hi bockon book on habit and instinct advanced the theory that while the calls and alarm notes uttered by bird birds are ably due to simple instinct their songs may be traditional that is banded doa down n from generation to generation and perpetna perpetuated ted through the faculty of imitation |
