Trans. Acad. Sci. of St. Louis, \*<>i.. XI. 



Plate X. 



17, Fkom a Normally Exposed Plate (Fin. 2). 



IS. From a Plate Over-Exposed 11,500,000 Times (Fig. 16). 



DIRECT AND REVERSED PHOTOGRAPHY. 



WESTERN ENGR. CO., ST. 



