To the Editor of the "NontH-Cuina Datty New:
Sim—Re the letter by "Astro!" on "100 per cent, moist," will you allow me to enlighten your corres pondent?
'There are two kinds of "humidity' in meteorological parlance:
(1) Absolute humidity expressed in weight of water vapour present in a given volume of air, Say, 80 many grains of water per cubic foot of atmospheric air.
(2) Relative humid of expressing humidity is very generally used in Public Health work. It is a relation between two quantities. (a) The weight of water vapour present in given volun.e of atmospheric air. (b) The maximum weight of water volume of air is under the same atmospheric conditions of temperature and pressure. The relation between A and His expressed in terms of percentage, Of one half, it is 60 per cent; if saturated, it is 100 per cent.
Life is'well able to exist atmosphere saturated with ture. If the temperature drops in given region where the relative humidity is near to saturation, the weight of vapour actually presen: in a given volume of air comes to exceed the weight the atmosphere capable of holding as vapour under the new conditions,. Condensa~ tion fakes, place, with motion of
Text read from the printed page and cleaned; old type leaves the occasional error.