. Western agriculture. r exhaled in thesummer time. When the air iscold this is condensed to a cloudwhich is nothing more than anaggregate of very small dropsof water. The clouds to beobserved in the sky are identi-cal in appearance and structurewith the one j ust mentioned andare also formed by the coolingof the moisture-laden air, dueeither to mixing with colder airor much oftener to rising tohigher altitudes. Just as thelittle particles of dust floataround in the air for days onaccount of the resistance of theair to their fall, before theysettle, so these little drops fallvery slowly on acc
. Western agriculture. r exhaled in thesummer time. When the air iscold this is condensed to a cloudwhich is nothing more than anaggregate of very small dropsof water. The clouds to beobserved in the sky are identi-cal in appearance and structurewith the one j ust mentioned andare also formed by the coolingof the moisture-laden air, dueeither to mixing with colder airor much oftener to rising tohigher altitudes. Just as thelittle particles of dust floataround in the air for days onaccount of the resistance of theair to their fall, before theysettle, so these little drops fallvery slowly on account of theuprising air current that causedtheir formation and on accountof their smallness. Iftheycool further, and the drops enlarge, they fall faster, andwe say that it rains. When the air is colder than the freez-ing point, snow or hail result. Cause of Winds. All points on the earth are not equallyheated, but more heat is received at the equator that atpoints north or south of it; and, at the same latitude, land %. Figure 21.—Standard rain and snowgauge. 64 WESTERN AGRICULTURE gets warmer than the adjoining water even though land andwater receive the same amount of heat. The air from thehotter area expands and flows over at the top upon the ad-jacent air, making the air pressure greater where the extraair is, and less in the section whence it came. Thus, on account of the unequal heating,differences in air pressure are setup and the air then flows fromthe points of high to the pointsof low pressure, causing winds. Weather Observations. Stormand clear weather areas are usu-ally in the form of great circularrotating whirls of air of severalhundred miles in diameter. Theyusually form in the western partof the United States or enterfrom the Pacific Ocean and traveleastward across the country, oftengetting nearly to Asia before theybreak up. Their position isdetermined as follows: At the same instant each dayand at widely separated stations careful observations of theconditio
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectagriculture, bookyear
