The forehead is more vaulted, and the brain, as might be expected from the intelligence of the animal, larger than in any other ape. The tusks a-e much smaller, and the whole of the teeth mate a close approxima tion to those of the human species. FINE MEASUREMENT. As an example, to show the degree of accu racy to which time has to be measured in order to obtain the velocity of a projectile to a foot per second, the following may be given : With a shot whose moan velocity between two screens placed 180 ft. apart is 1800 ft. per second, a variation of Ift, above or below 1800 ft. per second is represented by a decrease or increase in time of only 0 0005 of a second approximately. Such accuracy can only bo obtained by a careful elimination of the sources of error in the instrument used. The muzzle velocity is obtained from the recorded velocity by means of Barhford’s tables, a factor being employed which varies with the form of head of the projectile —Capt. Holden. GOOD EYESIGHT OF INDIANS. Dr L. Webster Fox is of opinion that savage races possess the perception of colour to a greater degree than do civilised races. In a lecture lately delivered before the Frank lin Institute, Philadelphia, he stated that he had just concluded an examination of 250 Indian children, of whom 100 were boys. Had ho selected 100 white boys from various parts of the United States, he would have found ot least five of them colour blind ; among the Indian boys he did not discover a single case of colour-blin Iness. Some years ago he examined 250 Indian boys, and found two colour blind, a very low percentage when com pared with the whites. Among the Indian girls he did not find any. Considering 'hat only two females in every 1000 among whites are colour blind, he dos not think it sur prising that he did not find any examples among the Indian girls. CITY FOG AND COUNTRY FOG. A fog becomes a useful indicator of the relative purity of the atmosphere in which it forms. 