( Continued frotn jtage 3 of cover,) 



VOLUME 57. 



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



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



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



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



3. Bridgman, p. W. — The Effect of Tension on the Electrical Resistance of Certain Ab- 



normal Metals, pp. 39-66. In press. 



4. Bell, Louis. — Notes on the Early Evolution of the Reflector, pp. 67-74. February, 



1922. $.50. 



