636 MR E. M. WEDDERBURN AND MR A. M. WILLIAMS. 



When we consider the roughness of the methods used, the closeness of this value to 

 the value previously obtained is wonderful. Still more wonderful is it that the period 

 agrees so closely with the observed period, for a difference of -0001 in the density of 

 one of the liquids would alter the period by about 5 per cent. — that is, by one hour in 

 twenty. 



PART IV. 



Experimental Verification of the Temperature Seiche Theory. By 

 E. M. Wedderburn, W.S., and A. M. Williams, M.A., B.Sc. 



(MS. received December 5, 1910.) 



§ 35. A number of laboratory experiments* were carried out to test the accuracy of 

 the foregoing theory, one particular object being to determine the effect of a gradually 

 sloping shore at the end of the lake, for the theory indicates that the period of the 

 temperature seiche will be the same whatever the sliape of the ends of the lake beyond 

 the points where the surface of separation between the upper and lower layers of 

 water ends. 



§ 36. All lakes which have the same temperature normal curve have the same period 

 for the temperature seiche, so that any lake can be represented by a basin of uniform 

 breadth, rectangular cross-section, but varying depth. 



§ 37. In a lake of parabolic longitudinal section the temperature normal curve is 

 not parabolic. Assuming rectangular cross-section, if a be half the length of the surface 

 of separation of such a lake, h the maximum depth of the lower layer, and h' of the 

 upper layer (which is uniform), then the temperature normal curve is of the form 



a' 



y = 



We may, however, assume that the curve is of the form 



h'Jifl 



(1) 



• (2) 

 ph + ph 



which is parabolic, and apply a correction for the deviation of (1) from (2). The y of 

 (1) is always greater than that of (2). 



§ 38. The necessary correction is arrived at graphically as follows : — The four 

 curves of fig. 6 represent the temperature normal curves of four symmetric lakes — 

 (1) consists of two straight lines, (2) is a parabola, (3) a curve of the form 



* The experiments were carried out in the Physical Laboratory of the University of Edinburgh, and most of the 

 observations were made by Mr Williams. The cost of the apparatus has been defrayed by a grant from the Moray 

 Fund of the University of Edinburgh. 



