BAROMETRICAL TABLES. xHii 



Then since Z = 62,20 feet we have 



62583.6 (log^l^ ~^°^'^) =6320+160 = 6480. 



From Table 51 for 5 = 23.61 in., we have 



62583.6 log ^ =6-^20, hence 



20 Q 

 62583.6 log p =6420 — 6480= —60. 



-Do 



Referring to Table 51 for the value of- Bo corresponding to this, we find 



.60 = 29.966 in. 



See "Example: (Metric Measures)," p. Hi. 



Let, the barometric reading (reduced to 0° C), i? = 655.7 mm., 



the mean temperature of the air column, ^=I2?3 C, 



the mean vapor pressure of the air column, e = g mm., 



the latitude, <j> = ^2°, 



the altitude of the station, Z=i379 meters. 



The equation for computing Z is simplified to the closely approximate form 



(from p. 1 ; for metric vmits) 



760 760 



Z-Z 



18400 (^ log -^ -log ^ 



^ /. r, <^ / N Z + 2ho 



0.00367^ + 0.378-^ +(y + rj)+ ^ 



wnere the terms are as defined on pp. xliv-xlvi. 



Again calling the terms in the bracket (a), (b) , (c) and (d), respectively, 

 to compute Bq we have : 



from Table 59, with ^=1379 n^- and ^=I2?3 C, Z(a) =62 



from Table 60, with Z=i379 m. and e = g mm., Z{b)= 7 



from Table 62, with ^=1379 m. and (/) = 32°, Z(f ) = 5^ 



from Table 63, with Z=i379 m. and Iio = o, Z{d)= o 



Z[{a) + {b) + {c) + (d)], =^ 

 Since Z=i379 m., we have 



18400 (^ log -^ -log-^j =1379-74= 1305- 

 From Table 56 for ^ = 655. 7 mm., we have 18400 log-p— =1179, hence 

 18400 log ^ =1179- 1305= -126. 



■Do 



Referring to Table 56 for the value of Bo corresponding to this, we find 

 B = 772.1 mm. 



There are no difficulties connected with the use of these tables to reduce 

 barometric readings to sea level, but serious difficulties are often encountered 

 in attempting to determine and e from observations at the elevated station 

 only (see pp. xxxiii and Ixxii). 



1 Indicated values for latitude and gravity correction apply only to mercurial ba- 

 rometers. For the case of aneroid barometers the v is omitted (see pp. xlviii and xlix). 



