CANADIAX FISUERIES EXPEDITION, J'Jl'rlJ 277 



less chance will there be for tiiis screwing movement of the water to develop, and the 

 iii'A-e insignificant the correction of formula (13) owing to rotation of the earth. 

 On the other hand, where the water in a current is homogeneous, the screwing movement 

 will develop to a greater degree, and there is then the risk that formula (13) may give 

 too high values for R. 



Formida (14) will likewise require to be corrected for the same reason. The 

 screwing movement of the water is naturally opposed by the friction, and the influence 

 of the friction upon the cii-culation does not therefore altogether disappear in the 

 case of closed curves drawn transversely across a current. In such curves, then the 

 earth's rotation will have two forces to overcome; that of the solenoids, and that of 

 the friction. Thus the velocities calculated according to (14) from the solenoids 

 alone will be too low; i.e., the values for velocity given in table 5 and plates XIV and 

 XV will be too small. The friction, on the other hand, will have no effect upon their 

 direction. By increasing these calculated velocities slightly, they can thus be made 

 more (.correct viz., the less stable the water layers are the more the velocities will 

 require to be increased. 



The most disturbing influence, however, which affects the velocities calculated 

 from formula (14) is that of the wind. The friction exerted upon the surface of the 

 water by wind corresponds to a very considerable value of R. This will naturally 

 be variable to a very high degree, but the direction in which it takes effect, and its 

 nature generally, will of course depend rather simply upon the direction of the wind. 

 By taking a few simple cases as examples, we may gain some idea as to the effect of 

 wind upon the distribution of density in a current, and the velocities thence obtained 

 according to formula (14). 



(a) Wind blowing in the forward direction of the current. — In this case, the velo- 

 city of the surface water will be increased, and the water in question consequently be 

 thrown off with greater force than previously to the right. In a section across the 

 current, the isostercs will become more vertical, and the number of solenoids. A, 

 greater. The calculated velocities will thus become greater, which agrees with the 

 increased velocity due to the action of the wind. In this instance, then the effect of 

 the wind will not greatly disturb our calculations according to (14). 



(fe) Wind Itlotving directly against the current. — The surface water will here be 

 retarded, and the force with which it veers off to the right will be diminished. The 

 number of solenoids in a section across the current will be less, and thus the velocities 

 calculated from the same will likewise be lower, agreeing, again, with the actual 

 decrease in velocity due to the opposing action of the wind. In this case also, then, 

 the disturbing influence of the wind upon the calculations according to (14) will be 

 but slight. 



(c) Wind hlowing crosswise to the current, and in a shoreward direction. — The 

 surface water is here driven with great force to the right; the isosteres stand on end, 

 and the number of solenoids in a section across the current will be abnormally increased. 

 The velocities calculated fi-om the solenoids according to (14) will therefore here be 

 too great. 



(d) Wind hlowing crosswise to the current, in a seaward direction. — With a slight 

 wind, the number of solenoids will be reduced, and the velocities thence calculated 

 according to (14) too low. "With a stronger wind, the entire current may be forced 

 away form the shore and out to sea. This gives rise to a highly abnormal distribution 

 of density and of solenoids, vide fig. 54 a, which on applying formula (14) gives the 

 distribution of velocities shown in fig. 54 b. This is here so abnormal that it does not 



