io8 TRANSPIRATION AND ASCENT OF SAP ch. 



Introducing the correction for the elastic yield of the 

 glass, this becomes 



T = 



(a-gO(* 2 -*i) 



0[i-a(* 2 -*i)] + 



i?-' 



k n 



where 



K = external radius of tube, 



r = internal radius of tube, 



k = compression modulus of glass (volume elasticity) = 4 x 10'" atm., 



n = torsion modulus of glass (torsional rigidity) = 3 x 10 5 atm. 



The value of a was obtained from the table of the volume 

 of water at different temperatures in Landolt-Bornstein, 

 Physikalisch-Chemische Tabellen, by E. Bornstein and 

 W. Meyerhofer, Berlin, 1905, pp. 38 and 39. The com- 

 pressibility coefficients /3 for different pressures and tem- 

 peratures are given on p. 60 of the same tables. 



Table 10. 



1 I am indebted to Mr. J. R. Cotter for adapting these formulae and 

 rendering them suitable for application to these experiments. 



