T.M. No. 25 - May 1951 



The Use and Accuracy of the Emery Settling Tube for Sand Analysis 

 by D. M. Poole, W, S. Butcher and R. L. Fisher 



The accuracy of the Emery Settling Tube for the analysis of sand 

 particles has been investigated. This method is more rapid than dry 

 sieving and gives equivalent, or settling, diameters rather than geo- 

 metric diameters. The paper confirms the reproducibility of the 

 results obtained from the settling tube, the close correlation with 

 sieve analysis, and gives a detailed recommended procedure. For size 

 ranges of most beach sands the accuracy of the two methods is nearly 

 the same. 



T.M. No. 24 - Apri I 1951 



The Accuracy of Present Wave Forecasting Methods with Reference to 

 Problems in Beach Erosion on the New Jersey and Long island Coasts 

 by W. J . Pierson, Jr. 



A study is made to determine whether or not wave forecasting 

 techniques can yield the observed values of wave parameters under 

 limitations of available data. Detailed weather data and wave data 

 were obtained for 22 April to 31 May 1958. In general, good agreement 

 between observed and forecasted significant wave heights is obtained. 

 Statistical study of results indicates forecasted significant periods 

 are not accurate and are not distributed according to the distribution 

 of observed significant periods. Forecasted values for deep water were 

 so inaccurate that verification of the refraction diagram for Long 

 Branch, New Jersey was impossible. Data are considered sufficiently 

 accurate to permit qualitative discussion of erosion problems. Some 

 effects of a storm on the shoreline are described, and statistical 

 properties of east coast storms given. 



T.M. No. 25 - November 1951 



The Slope of Lake Surfaces Under Variable Wind Stresses by B. Haurwitz 



The Inclination of a lake surface caused by a wind stress shows 

 a distinct time lag In adjusting itself to changing winds. This 

 phenomenon is analyzed using hydrodynamic equations simplified by in- 

 tegrating over the whole depth of the lake, and It is found a priori 

 th^t the time required depends on the length of the seiche periods. 

 Particular attention Is given to a wind shift which took place during 

 the passage of a hurricane, 26-27 August 1949, over Lake Okeechobee, 

 Florida, when the wind turned through about 180° during a time of 

 roughly three hours. The turning of the wind was accompanied by a 

 turning of the height contours of the lake surface, but the latter 

 rotated more slowly so that for some time the wind blew para I lei to 

 them. [t is shown that the theory explains this behavior of the 

 lake surface. 



