Results of Some Experiments Upon the Rate of Evaporation

Of the dozens of patterns of evaporators designed (and sometimes used) by different inventors, not one has hitherto been unreservedly accepted as a standard.Consequently, in the absence of any authoritative pronouncement, observers have used so-called gauges of ell sorts of sizes and all sorts of mountings.Niiturslly the results differ as widely as the methods, some showing a rate of evaporation fully twice as great as others.Nr.Baldwin Latham, for example, showed that his fine evaporation gauge made of copper, 1 foot in diameter, containing 1 foot in depth of water, and floated by means of a hollow copper ring, placed 6 inches distant from the body of the gauge-to which it was attached by radial arms-on a tank 4 feet in diimeter and 30 inches deep, gave an annual average evaporation of 19.95 inches ; whereas a copper pan, 5 inches in diameter and 12 inches deep, standing in air, lost 38-19 inches.:::In the Strathfield Turgiss experiments, again, the indicated evaporation for the six months April to September, 1870, varied between 20.64 inches from a large iron tank 6 feet square and 2 feet deep, sunk in the ground, to a trifle under 47 inches from a tin can 12 inches deep and 5 inches in diameter, standing upon the ground; some small pans under cover giving an annual average of about 14 inches at the same time.1 "Dr.Brownrigg fixes the evaporation of some parts of England at * Presidential hddress to the Royal Meteorological Society.