VALUE OF A SINGLE HAIR

Shannon News, 27 July 1928, Page 3

VALUE OF A SINGLE HAIR

A single hair from the unbobucd -ead of a filing clerk in of he Portland Cement-Assoeiati«B->s»

Chicago is playing an important role n experiments to test the strength of oncreto for building purposes. Knowledge about the effect of moisture on reat blocks of the heavy building maferial is dependent in a measure on his one - hair . (says ..the Christian kience Monitor). T£e slender filanenf regulates the humidity of "a laboratory room where tests arc made. Engineers at the association explaia hat its virtue lies in its extreme sensi iveness to moisture. iLet the air bi* ome a wee bit damp and the hair ?rows longer; let it dry and the hair hortens. So regular is its behaviour, hey have found, that it makes a use"nl little servant. ..Stretched between wo posts, it holds down one arm. of t» •.mall delicately balanced rod. When here is too much moisture in the room the hair elongates, lets the bar rise lightly and makes a contact with a ?an which begins at once to blow over oans of calcium chloride,» a substancr !;hat cats up the dampness. But shouW. Mic-air grow too dry, then zip! One set of lights goes off and anothoi flashes on. One fanstop6 and another starts, and a fresh batch of air from a humid room comes blowing in. The result of the.hair's'performance is thai the humidity of the room is kept nearly constant and this otherwise variable factor is pushed off the scene, making it possible to measure the expansion of concrete under-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 "stretches as much as one three-millionth of an inch, the microscope can catch it, thanks to the dependability of the hair.