WEATHER FORECASTS

Greymouth Evening Star, 23 June 1928, Page 12

WEATHER FORECASTS

VALUE OF A SINGLE HAIR

A single hair from the unbobbed head of «■ filing clerk in the oilice 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 exuviae. sensitiveness to moisture. Lot the air become a. wee bit damp and the hair grows longer; let it dry, and the hair shortens. So regular is its behaviour, they have found, that it makes a useful servant. Stretched between two posts, it holds down one arm of a small, delicately balance rod. When there is too milch moisture in the room the hair elongates, lets the bar rise slightly and makes a contact with

a f:iu which al once begins to blow over puns of calcium chloridi', a substance ihai eats up the duinpm-ss. Bm should th? air grow 100 dry. thou zip! Ono sot of light goes oft and another flashes on. One fan slops and another starts, and a, tresli batch of air from a humid •room comes blowing in. The result' of the hair's perform :neo is that the humidity of ihe room is kept, nearly constant and this otherwise variable factor is pushed oil the scene, making ii possible to measure the expansion of concrete after exposure to ihoisturc. Precise nmasuroment,.-- of concrete blocks are made before immersion and afterwards by means of iwo microscopes allmrhed to an invar shed bar. If Hi.' l concrete stretches so much as one tlireemillionth of an inch. Ihe microscope can catch if, thanks to ihe dependability of the hair.