WEATHER FORECASTS.

Wanganui Chronicle, Volume LXXXIII, Issue 20182, 26 June 1928, Page 9

WEATHER FORECASTS.

VALUE OF A HAIR TESTING CONCRETE BLOCKS. A single hair from the unbobbed head of a filing clerk in the office of the Portland Cement Association in Chicago is playing an important role in experiments to test the strength of concrete for building purposes. Knowledge about the effect of moisture on great blocks of the heavy building material is dependent in a measure on this one hair (says the Christian Science Monitor). The slender filament regulates the humidity of a laboratory room where tests are made. Engineers at the association explain that its virtue lies in its extreme sen--1 sitiveness to moisture. Let the air become a wee bit damp nnd the hair grows longer; let it dry, and the hair shortens. So regular is its behaviour, they have found, that it makes a useful little servant. Stretched between two posts, it holds down one arm of a small, delicately balanced rod. When there is too much moisture in the room the hair elongates lets tho bar rise slightly and makes a contact with a fan which begins at once to blow over pans of calcium chloride, a substance that cats up the dampness. But should the air grow too dry, then zip! One set of lights goes off and another flashes on. One fan stops and another starts, and a fresh batch of air from a humid room conies blowing in. The result of the hair’s performance is that the humidity of the room is kept nearly constant, and this otherwise vanable factor is pushed off the scene, making it possible to measure the expansion of concrete after exposure to moisture. Precise measurements of concrete blocks are made before immersion and afterwards by means of two microscopes attached to an invar steel bar. If the concrete streches as much as one three-millionth of an inch, the microscope can 'catch it, thanks to the dependability of the hair.