Tying Down the Desert.

Progress, Volume II, Issue 2, 1 December 1906, Page 67

Tying Down the Desert.

Over 150,000 acres of sand dunes in France, once blown about by the wind until they overwhelmed great stretches of fertile ground and even threatened to bury whole towns, are now covered with forests of pine, which produce turpentine, lumber, and charcoal.

A new apparatus for the determination of the mechanical equivalent of heat -was recently described by Herr H. Rubens in a German paper. A brass tube, 60 centimetres long and 4+ centimetres in diameter, closed at the end by insulating caps, through which project inwards the bulbs of two thermometers, is firmly fixed coaxially within a slightly larger highly polished and nickel-plated brass cylinder with closed ends, which can be turned into a vertical plane about a horizontal axis through its middle point. The inner tube contains a cylindrical mass lead, weighing over 4 kilos., of but slighty less diameter, and of nearly half its volume ; the remainder of the tube being filled with machine oil. Observation windows are provided so that the behaviour of the lead weight can be noted. The tube is quickly turned from its vertical position to another, halt is made for the short period needed for the weight to fall to the bottom of the tube, and the procedure is repeated, the rate of about ten turns a minute being possible. With this instrument the author has found J = 424.8 as a mean of ten observations with an average variation of 1 per cent, from the mean.