410 



RECORD OF SCIENCE FOR 1887 AND 1888. 



Tablk XIX. — No7inal distribution of aqueous vapor at various altitudes above the earth's 



surface. 



The total amouDt of moisture preseut at any moment in a column of 

 saturated air extending from sea-level up to the altitude of 6,000, 12,000, 

 etc., feet is found from the numbers given in the preceding table, and 

 is expres.sed in the followiug table, by the depth in inches of the corre- 

 sponding layer of water that would be formed if all the moisture iu such 

 column were to fall to the earth as rain : 



Table XXI. 



Besides the observation of local dew-point, the amount of moisture in 

 the whole layer of air above us can jjerhaps be directly determined, as 

 per example, by means of the spectroscope or the cyauometer, at each 

 station ; but as these observations have not as yet been reduced to a 

 system the Signal Service makes use of what is called a sunset obser- 



