Trans. Acad. Sci. of St. Louis. Vol. XI. 



Plate VII. 



£ a. 60,000 



11. Exposure, 60,000. Illumination. 0.197. 



£ ^ /% o ( O o o 





12. Exposuke, 120,000. Illumination, 0.063. 



DIRECT AND REVERSED PHOTOGRAPHY 



