POPULAR SCIENCE.

Gisborne Times, Volume XXX, Issue 3559, 26 June 1912, Page 8

POPULAR SCIENCE.

LUMINOUS ADVERTISEMENTS. One of the many advertising ideas that have gained a vogue in America is'the luminous pavement sign. A pit for electric bulbs is cut beneath the'pavement, and is covered with a thick glass slab bearing the lettering of the. design. Most of the signs are constructed to flash out and in, and it is rather startling for the pedestrian to suddenly step on to a vivid band of light which gives the impression that the pavement is on fire. So far the scheme has not been adopted in England. AGE OF THE EARTH. In the course of the'r annual review of the progress of research at the Imperial College of Science and Technology, the governing body of that i iV’tution refer to the very interesting results achieved by Professor Strmt, F.R.S., in connection with the measurement of geological time by radioactive methods. Search has been made for minerals containing a- great amount of helium relative to the radioactive matter present, and in some cases ages as great as 700,000,LA0 years are indicated for the minerals. A direct measurement of the rate at which helium is formed in thorhniie amt pitchblende has been carried v- a satisfactory conclusion. '•!'s investir;; tion fully confi 1 ms theoretic-.! amici] atoms, and gives the oaie atic-i >-f geAgical ages an increased sir. i -7 dircetn „,s. TO SAVE THE POSTMAN. In the suburbs of American cities the houses often stand a long distance back from the road. To save the postman, a post about three fbet high is placed in front of each house on the road, and a small weatlier-proot box is fitted to this, with a slit large enough to allow letters to he inserted in it- On one end of this box is a metal flag hinged on so as to stand erect op lie flat on the box. When the postman has a letter he deposits it in the box, and then lifts the flag to an upright position. A resident has thus only to watch the box, arid' if the flag is raised ho knows there is some mail for him. Each box, of course, is inscribed with the owners name on it. TEETH AND BRAINS. In a "lecture, Dr. N- Bishop Harman, F.R.S.C., has pointed out that there are signs of a steady degeneracy in two sets of organs vital to the wellbeing pf the human race, and the fall is most marked among the Western nations. The-evidence is that, coincident’ with the mental advance of man, there has been a diminution in the provision of teeth. In the ape, the negro f an,d the white man, brain and teeth are inversely proportional to efficiency. Increase of cunning has reduced the work of the: teeth, and the demand of the brain lor blood has starved the' former; disorder of digestion show that the balance as unsatisfactory.