460 CARNEGIE INSTITUTION OF WASHINGTON. 



by submerging the whole of the gravitational apparatus in a capacious 

 water-bath well stirred, so that the temperature varied but a few tenths 

 of a degree per day. Notwithstanding these apparently ideal condi- 

 tions, the needle simply drifted and showed no response to gravitation 

 whatever. The best method of reducing the radiation discrepancy, 

 thus far found, is an exhaustion of the case containing the needle. 

 Results so found came within 1 per cent of the normal value, but were 

 still in excess. No doubt this is far from precision; but it is a great 

 advance from the original error of several hundred per cent of excess. 

 In concluding papers the author has put together a number of in- 

 cidental results, bearing on the breakdown of molecular instabilities 

 as evidenced by the peculiar phenomena of residual viscosity. In a 

 similar experiment, showing the magnetic set in iron produced by an 

 electrical current passing through it, there occurs, as it were, an ele- 

 ment of hysteresis. A useful method for the production of two groups 

 of independent fringes, present in the same field, is finally given. 



Hayford, John F., Northwestern University, Evanston, Illinois. Investi- 

 gation of the laivs of evaporation and stream-flow. (For previous reports 

 see Year Books Nos. 12-16, 19.) 



One year ago the investigation had reached the stage in which it was 

 clear that the next step must be to complete the evaluation of fluctua- 

 tions in elevation of the water-surface at each recording-gage, from day 

 to day, due to the variations in direction and in velocity of the winds 

 blowing over the surface of each lake and the variations in the baro- 

 metric gradients over that lake. The ultimate object of this investi- 

 gation is to obtain a much better formulation than the engineering- 

 profession now has of the laws governing the amount of stream-flow. 

 The immediate object of the investigation is to determine the laws of 

 evaporation from a large water-surface with much greater accuracy 

 than they are now known. For this purpose it is proposed to consider 

 each of the Great Lakes in turn as an evaporation pan and to evalu- 

 ate change of content, income, and outgo, including evaporation. 



One year ago the evaluation of wind effects had made much progress,, 

 but was far from complete. It is now complete. 



During the year the evaluation of the barometric effects on Lakes 

 Erie and Lake Michigan-Huron has been completed. 



A publication setting forth fully the results of this part of the investi- 

 gation is now ready for the printer under the title, "Effects of Winds 

 and of Barometric Pressures upon the Great Lakes." 



The effects on the elevation of water-surface of changes in the baro- 

 metric gradient over each lake have been found to be larger than they 

 have ordinarily been supposed to be. For example, the barometric 

 gradients over Lake Michigan-Huron caused the water-surface at the 

 Milwaukee gage to be above, or below, the mean elevation of the sur- 



