dinension of gravel whose order of magnitude is still in accord 

 with observed reality for said limiting velocity of erosion, on 

 horizontal bottoms, of 1 m/sec, in spite of the enormous ex- 

 trapolation roade.$. which it would not be permissible to carry on 

 indefinitely. The formula gives acceptable results, without 

 modifying the constants from those applying to stones or blocks of 

 several. tons weight, to these gravels that don't weigh 100 grams. 



As a consequence of the foregoing, we estimate that we have 

 confirmed authentically, through direct observations which always 

 constitute the definitive ratification of these matters of techno- 

 logy, the generalization of the formula and the values of its 

 coefficients, despita the simplifications whose introductions in 

 these complex subjects are unavoidable. 



ANNOUNCEMENT OF PUBLICATION 



The Beach Erosion Board announces the publication of its 

 Technical Memorandum No. 21, "The Interpretation of Crossed 

 Orthogonals in Wave Refraction Phenomena". Copies are being 

 mailed to those individuals and institutions on the mailing list 

 for technical publications. 



A limited number of copies are available for distribution 

 upon request to the President, Beach Erosion Board, Corps of 

 Engineers, 5201 Little Falls Road, N. W., Washington 16, D. C. 



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