"EVAPORATION."

Dominion, Volume 2, Issue 451, 9 March 1909, Page 2

"EVAPORATION."

HOW IT IS MEASUREIJ. GOOD HOBBY FOR FARMERS' SONS. . In these dry days, when farmers an ga& nig en land that is daily' growing more parched, the speed at which tho moistiro is evaporating from tlio soil must prcseit itst'lf as an interesting speculation. Tlk rate of evaporation can be nioaeurod by a ample Jioine-niado instrument, which some o ! our iarmers or their resourceful young sous may like to make. ' I'lio evaporimetcrs used in tlio Now York mtamcal Gardens, similar to those now distributed all over America, consist of a pint rruit-jar, tightly corkod with a cork simper soaked in paraffin. Through tho stopper a glass tube extends from tho bottom of the jar up and through a secoirl cork, which tmnu.V closes the opening intra porous clay thimble. The glass tubo oxtcids f to tlio top of tho thimble. For furtlnr protection against the entrance of water from withnit, a paraffined piece of cloth wai fitted tigitly around tho glass tube, aud (xtended a-, a roof ovor the top of tho fmit-jir. When wt out for use the jar was filled with distilled water up to zero mark. an 3 tho powus thimble and tho glass tube wcro also filed with distilled water. Tho ovalorimotor las this instrument is called) was iunk into the ground to tho level of tho top of tho fruit jar. As evaporation took pliCo from t!io surface of the thimble the wacr rose from the jar up through the glass tub, thus keeping tho thimble full and loweriii; the surface of the water in the jar. The rafe of ovaporition varied with tho relative huiiidity of the surrounding air, and the aniouit was measured by carefully pouring mere, distilled water into tho jar from a grtduato, until the water surface in the jar raso again to zero mark. The amount of va'.er necessary to accomplish this was tho noasuro of tho ■amount of evaporation for th( given period. Tho rate of evaporation varic according to locality, aspect, weather, etc. In the New York Botanical Gardens the rainfall. in a given period was 9.32 inches, and tho evaporation in the same period reorded by tlio instrument was as follows: —Or a dry rocky knoll 0.85 inch loss than- the ninfall; on low swampy ground, 4.48' inches less-, than tlio rainfall; and on a garden 50ft distant from the swamp, 2.78 inches less-ban tho rainfall.. _ : By means of the' instrumentdescribed, extended investigations on evapcation are being carried out all over the Tnited States. The making of tho insi-rumoii and its uso would bo an interesting hobbyfor tho studious sous of some of our farntrs, and form a valuable part of their agrialtural education.