To the Editor of the "Nomni-Ciano Dany Neves Sw—The principle of producing 2 cooling effect by evaporation Is based on the so-called wet-bulb depression. When' you have two. thermometers Sethe nara with which Jou faking. your daily Teadings, and the term which the mercury bulb is Covered. with a piece of clean sft Sloth which has been dipped Into Svater, then you will observe that the Second thermometer shows a. lower Feading.. This latter temperature tilcalled the wet-bulb temperature and the other the dry-bulb temperature. The difference between these two temperatures is dependent on the Felative humidity of the alr.
Tu the Egyptian desert where there 4s, for instance, a relative humidity of 28 per cent, you can lower the tem~ perature from 95° F. to max. 09 F. Tu Shanghai, with a relative humidity fof 60 per cent, and 95° F. you can Tower the temperature to 8% F, not more. If you have 85°F. and 90 per cent. relative humidity, then you can Tower the temperature to max. eis" F, This principle is based. on the transformation of the sensible hheat of her alr into latent heat of the air (evaporation).
"For the box you can take a material which has a good heat conductance, for instance, copper, aluminium, ete. The covering must be soft, always julean, cloth which will hold the water, and perforated gauze for letting the air through, which is important, My opinion is that you Will have no success in producing a cooling effect by evaporation, since the relative humidity in this' region 'A, Scumeroen, Shanghai, Mar, 6
Text read from the printed page and cleaned; old type leaves the occasional error.