i6 Citiciiniati Society of Natural History. 



to absorption of radiant heat by vapor of Avater is worthy 

 of reference: "Aqueous vapor is a blanket, more necessary 

 to the vegetable life of England than clothing is to man. 

 Remove for a single Summer night the aqueous vapor from 

 the air, which overspreads this country, and you would 

 assuredly destroy ever}^ plant ca])able of Ixing destroyed 

 by a freezing temperature. The acjueous va])or constitutes a 

 local dam, by which the temperature at the earth's surface is 

 deepened." 



In the air, .saturated, or nearly .so, with moisture, you have 

 less barometric pressure, less oxygen and a warmer tempera- 

 ture. All of us have experienced such weather. The exces- 

 sive humidit}^ invests us so that the natural transpiration 

 through the skin and lungs is obstructed, the oxygen is dimin- 

 ished and retention of carbonic acid is increased, and we are 

 enervated. The deposition of this excessive moisture, in the 

 form of rain, is a great relief from the depression caused by 

 the previously existing humidity, low pressure and calm. It 

 cools and purifies the air by allowing more evaporation and 

 bringing down the impurities of the air. 



WIND. 



Wind is air in motion, arising from differences of tempera- 

 ture a.nd largely determined and directed by differences of 

 barometric pressure between two places or regions more or 

 less remote from each other. It promotes evaj^oration, and is 

 cooling on the surface or individuals within its range. It 

 tempers the heat of vSummer and removes bodies of vapor that 

 may be interfering with radiant heat. It removes, for the time 

 being, the foreign or accidental products in the air. Its inter- 

 connections are with temperature and humidity ])rincipally. 

 A cold, damp wind in Winter, such as we know our north- 

 easters to be, is very trying to our feelings and vigor, and 

 are the dangerous winds to the infirm or the aged, even. A 

 warm wind is a pleasant change from a close, nuiggy, stifling 

 and calm atmo.sphere. The south-west wind is the rain-bear- 

 ing wind of our latitude ; the south the warm one ; the north 

 and the north-west the cold and dry, or anti-cyclonic ones. We 

 have thus imperfectly gone over some of the relations of the 

 units of weather to the individual. 



