72 EFFECTS OF WINDS AND OF 



(1) The barometric effects as computed have in general, barring certain 

 classes of exceptional cases referred to in (4), the degree of accuracy indicated 

 by the computed probable errors. 



(2) There are decided modifications of the barometric effects, due to the 

 configuration of the shores and bottom of the lake, which modifications are 

 peculiar to each gage station and in general increase the magnitude of the 

 effects. 



(3) The errors in assumption No. 2 probably contribute to making P w 

 and P n greater than +1.00. 



(4) At times, when the changes in barometric gradients are unusually rapid 

 and irregular, such as the times when a well-developed low-pressure area is 

 passing over or near a lake, the errors in the computed barometric effects are 

 probably abnormally large. At such a time the shape of the wave produced 

 on the lake surface by barometric changes is unusual, and therefore one may 

 expect the modifications in it due to inertia and dependent upon the con- 

 figuration of the shores and bottom to be unusual. 



CONCLUSIONS ON ACCURACY OF COMPUTED BAROMETRIC EFFECTS. 



A comparison of each final least-square solution, such as L2 at Buffalo, 

 'With earlier least-square solutions, furnishes very valuable and instructive 

 evidence as to the accuracy and reliability of the conclusions from the final 

 solutions. But such evidence is made up of many details and many con- 

 siderations of such a character that they can not be briefly presented. Hence, 

 it must suffice here to state that such evidence furnished strong corrobo- 

 ration of the foregoing discussion of the errors in the computed barometric 

 effects. 



The general conclusions, based upon all the evidence available, which 

 have been reached in regard to the computed barometric effects at the five 

 stations Buffalo, Cleveland, Milwaukee, Harbor Beach, and Mackinaw are : 



(1) The errors of the computed daily barometric effects are probably less 

 than 5 per cent of said effects in about one-half of all days. 



(2) On a small percentage of exceptional days, at times when the baro- 

 metric gradients are changing rapidly and irregularly, usually when a well- 

 developed low-pressure area is over or near the lake, the computed baromet- 

 ric effects are subject to abnormally large errors, much greater than 5 per 

 cent. These exceptional days are usually solitary, not in groups. 



ACCURACY OF COMPUTED WIND EFFECTS. 



As shown on page 63, the final value adopted for the constant C x of the 

 fundamental formula for wind effects (51) on page 39 was +0.088, which 

 gave as the definite numerical formula for wind effects (69) on page 63. 



What is the accuracy of the value +0.088? This value is a weighted 

 mean of four separate values from four separate least-square solutions, as 

 shown in table No. 13, page 63. Its probable error is 0.006, as there 



