(Continued from ptige 3 of cover.) 



VOLUME 57. 



Kent, Norton A. and Taylor, Luchen B. — The Grid Structure in Echelon Spectrum 



Lines, pp. 1-18. December, 1921. $.75. 

 LoTKA, Alfred J. — The General Conditions of Validity of the Principle of Le Chatelier. 



pp. 19-37. January, 1922. $.75. 



