H. Moore, of St. Helens, has investigated the effect of blast on windows by instantaneous photography. His pictures reveal the operation of the two pressure waves caused by the bomb, the sharp and short wave which comes first and the following less intense but longer suction wave, writes the Scientific Correspondent of the "Manchester Guardian." The first wave pushes the windows inwards and cracks the glass. But before the separate pieces have time to fall it is past and the slower suction wave, acting in the opposite direction, comes into play. This pulls the pieces outwards. Hence blast knocks the window glass into the room only when the bomb is very near. At greater distances the pieces of glass generally fall outwards, because the direction is determined by the suction wave, which acts towards the bomb.
Roof-lights painted black are liable to crack in strong sunlight. Investigation proved that the cracking was not due to differences of temperature between the sides of the glass, due to the sun shining on the top side only, but to differences in temperature between different regions of the surface. Cracking could be avoided if all parts of the glass, and especially those near the edges, were exposed to the same amount of radiation as the centre and if the fixing at the edges was not more rigid than the putty ordinarily used.
A new vitamin is suspected, the anti-grey hair factor W. Its existence seems to be indicated through researches on dogs and chicks. If this is confirmed and pure extracts of factor W are obtained, leading to the determination of its chemical structure and subsequent synthesis, followed by commercial production, a new line among the bottles of the hairdressers' shops will appear.
It will add one more difficulty to the pressing problem of the best method of administering vitamins. Should they be obtained by changing the diet and taking unfamiliar or different proportions of food, or should synthetic vitamins be added to customary food which has been devitaminized by industrial processing? C. A. Elvehjem states in "Nature" that a pork sandwich made with white bread may supply more vitamin B than a jelly sandwich made. with whole-wheat bread. The advantage of acquiring vitamins by suitable choice of food rather than by taking a synthetic product from a bottle is that food probably contains many important factors that have not yet been recognized, while the pure synthetic products contain nothing except factors that are known.
Text read from the printed page and cleaned; old type leaves the occasional error.