530.1 R Ruark , Arthur Edward , 1899- Atoms , molecules and quanta , by Arthur Edward Ruark and Harold Clayton Urey. New York (etc) McGraw-Hill book company , 1930. xvii , 790 p. ilus. , diagrs. 24 cm (Half-title : International series in physics) " References " at end of most of the chpters ; Bibliographical foot- notes.