( 58 ) 



1 



KT 



where (> is the density of' the air, K the gasconstant, 7' the absolute 

 temperature of the air and />„ the average atmospheric pressure 

 expressed in mm. mercury-pressure, and taking: 



A'= 2.87 X 10" , T - 283° . />„ = 700 , n = 7.3 X 10"^ 

 we have the (piantities H to divide by 



1.464 X 10'" 

 in order to obtain the gradient expressed in mm. mercury-pressure 

 per cm., or by 1319 if we wisli to express the gradient, as usual, 

 per 111 km. In order to avoid the use of very small quantities, 

 this division has not been made and the quantities i:? are considered 

 as gradients. 



Table IV shows the diurnal variation of the gradient as calculated 

 in this way. As the wind observations made on board of the light- 

 ship Terschellingerbank are made with respect to the magnetic 

 meridian, the direction of the resulting gradient ought be counted 

 from the same. 



TABLE IV. 



Monodiurnal variation of the Gradient, time counted from noon, 

 //, to North, H^ to South. 

 R. L. Veeriuii' to right and left, 

 d e Bilt. Terschellingerbank. 



(magnetical) 

 Winter i^, = 4.5^0.^'^^— 273°.3) A^ //^ = 12.3cö5(?z/— 305°.l) L. 



ti.,— TX.xycos{nt — 42°.5) 

 A = 230°.8 



Spring H^ = 3.1 cos {nt— 35°.0) R. 

 H,= 92.5 6-06- (yz^ — 44°.3) 

 A = 350°.7 

 Summer ^1= 'è'6.bcos{nt— o3°.4) L. 

 H, = 129.3 cos {nt — 42°.5) 

 A = 10°.9 

 Autumn H^= 16.6ct;6(?z/— 273°.l) Z?. 

 H.= 'ol.Q cos {nt- 



Year 



46°.l) 



H,= S.l cos {nt — 211°. S) 



A = 93°.8 

 H, = 12.2 cos {nt=300°.7) R. 

 H, = 23.3 cos {nt — 25°.2) 



A = 275°.5 

 //, = 23.5 cos {nt—34t6°.2) R. 

 H, = 32.4 cos (?i^ — 355°.5) 



A = 350°.7 

 H, = 11.9 cos (71^— 330°.2) R. 

 E, =: 18.9 cos (72^— 354°.9) 



A = 335°.3 

 H, = 14.6 cos {7it—31 2°.3) R. 

 h[ = 20.0 cos {lit — 0°.3) 



A = 312°.0 



