72 CONSTRUCTION OF ISOBARIC CHARTS 



Nos. 2 and 3, respectively, the pressure and temperature registered at these hours [the 



local pressure expressed in inches of mercury under standard gravity. — C. A.]. 

 No. 4, the values of (/j — t) for these pressures and temperatures as obtained from 



Table 7. 

 No. 5, the registered relative humidities. 



No. 6, the values of {t^ — t) deduced from Table 8, for the data in columns 4 and 5. 

 No. 7, the tr or the sum of the {tr — t) in column 6 and the temperatures t in column 3. 

 No. 8, the observed elevations computed trigonometrically. 

 No. 9, the values of the gravity potentials V obtained from No. 8 by means of Table 3. 



From the t^ and Fin columns 7 and 9 the {t„ V) curve of Fig. 1 is constructed 

 and along side of it the corresponding extrapolated curve for 8 A. M. as in Fig. 2. 

 From the {t,., V) curve for 8 A. M. we read off the mean values of tr for the intervals 

 F= 18 550 to 7= 20 000, F= 20 000 to F= 30 000, etc., and proceed to the follow- 

 ing columns : 



No. 10, the ordinal numbers of the level surfaces of gravity. 



No. 11, the mean values of t^ for the intervals between the surfaces of column No. 10. 

 No. 12, the values of n!> for the average t^ as given by Tables 10 and 11. 

 No. 13, the value of jj,. for each level surface obtained by successive algebraic addi- 

 tions of IT \'l to the reading of the station-barometer at 8 A. M. 

 No. 14, contains the values of t^ for the level surfaces, F= 18 550, F= 20 000, etc. 



at 8 A. M., obtained directly from the extrapolated {t„ F)-curve of Fig. 2. 



From the values of p^and t^ given in columns 13 and 14, the curve of Fig. 3 is 

 constructed and from this the mean value of t^ for each half-inch of barometric change 

 is read off. 



No. 15, contains the barometric pressure for each of these half-inch intervals. 

 No. 16 gives the corresponding mean values of i^- 



No. 17 gives the values of E^- for these <,.-values, obtained by aid of Tables 9, 12 and 13. 

 No. 18 contains the values of Vp, that result from successive additions of the values in 



column 17 [to the value of Vp for the level surface that contains the station 



barometer. — C. A.]. 



From the curves in Figs. 2 and 3 there may also be determined the values of t^ 

 for the isobaric surfaces at 8 A. M., and for the level surfaces of gravity at the 

 moments when the kite passed through them. 

 No. 19 contains the values of t^ at 8 A. M. read off from the curve of Fig. 3 and 



corresponding to the isobaric surfaces given in column 15. 

 No. 20 gives the ordinal number for each 10 000th level surface of gravity. 

 Nos. 21 and 23 give the times when the kite passed through each of the surfaces 



given in column 20, ascending and descending respectively. 



