o84 SHORT MEMOIRS ON METEOROLOGICAL SUBJECTS. 



The formula for Q further teaches us that one-half of the whole quan- 

 tity of aqueous vapor is contained in the strata of air below the altitude 

 of 1,9G2 meters, or 6,043 Paris feet, and that only one-tenth of the whole 

 aqueous vapor in the atmosphere is above the altitude of 6,500 meters, 

 or 20,000 Paris feet. Strachey is therefore right in saying that the 

 mountain-ranges, however slight their altitudes are in respect to the 

 dimensions of the whole globe, yet must be of great influence in refer- 

 ence to the aqueous meteors. A mountain-chain of only 6,000 feet alti- 

 tude forms a dividing barrier for one-half of the vapor in the atmos- 

 phere; the Himalayas, with an altitude of about 15,000 feet, or 4,600 

 meters, cuts off eight-tenths. 



lu conclusion, 1 would expressly remark that the formula deduced for 

 the diminution of vapor-tension with altitude can only be applied with 

 security to the computation of mean ratios. It can also be practically 

 applied in barometric hypsometry, since all the more recent hypsometric 

 tables take into consideration the aqueous vapor of the air, but fre- 

 quently the vapor-tension is known for only one of the two stations 

 whose relative altitude is to be determined. The following- example 

 shows that for this purpose the accuracy of the formula is quite sufficient. 

 Bauernfeind observed the psychrometer twenty-one times daily during 

 tive days at five stations on the Greater Miesing, whose relative alti- 

 tudes were determined by direct leveling. (See Beoh. und TJnters. ilber 

 die Genaulglceit barometrischer HoJienmessimgeii, Mtinchen, 1862, p. 132.) 

 The following small table contains the means of these observations, and 

 beneath them are given the values computed by our formula for the 

 other stations from the observations at station I : 



Stations I. II. 



Altitude in meters 816 1086 



2) observed, Paris lines . . 5.16 4.30 



p computed from I — 4.09 



We shall be perfectly satisfied with the agreement between observa- 

 tion and computation if we reflect that Baurnfeind's observations were 

 not used in the deduction of our formula, because they appeared to us 

 to relate to far too slight an altitude. 



[Note. — The mean vapor-tension in Klageufurt is 7.1 millimeters. 

 Hence, for the station Hoch-Obir, lying 1,603 meters higher, is computed a 

 mean vapor-tension of 4.03 millimeters. Prettner (Kiima von Kdrntlien, 

 p. 163) gives for Hoch-Obir a relative humidity of 82 per cent, and a 

 mean temperature of 0o.85 C, according to psychrometer observations, 

 for one year, 1852. To these figures there corresponds a vapor-tension 

 of 4.02 millimeters; therefore, exactly equal to the computed value.] 



Notwithstanding the agreement between observation and computation 

 iu these and other cases, no deeper theoretical meaning should be attrib- 

 uted to our formula. It is perhaps only a more exact expression for the 

 opinion expressed by Strachey, that the average degree of saturation of 



