RECORDS OF MEETINGS 357 



now afford remarkably satisfactory lantern slides of colored minerals 

 of either cabinet or microscopic size. 



The methods of production of all these plates were explained, but in 

 the writer's experience the Jougla and Dufay plates seemed to afford 

 slides preferable in transparency and resistance to the heat of the 

 lantern. 



Photomicrographs in color of thin sections of rocks and minerals by 

 transmitted polarized light were made by Francois Frank on Lumiere 

 plates as early as the year 1907 (Ch. A. Francois Frank, "La Micro- 

 photographie en couleur avec les plaques autocrome de M. M. A. et 

 L. Lumiere," Comptes Eendus l er Semestre, T. CXLIV, No. 24, p. 

 134L, 17 June, 1907). 



The first attempt to make photomicrographs, on autocolor plates, of 

 microscopic colored minerals by ordinary reflected light was made by 

 Mr. Frank La Manna, of the Borough of Brooklyn, JNT. Y., about Feb- 

 ruary, 1911. Mr. La Manna thus photographed on Jougla and Dufay 

 plates he brought from Paris several specimens of microscopic colored 

 minerals mounted in Eakestraws by the writer. (F. La Manna, Ex- 

 hibit at the Annual Beception of the Department of Microscopy of the 

 Brooklyn Institute, 11 March, 1911.) The deep black interior of the 

 Eakestraws served as a superior black background. 



Through the courtesy of Mr. La Manna, the writer received some of 

 these plates upon which he photographed other similar specimens. 

 These photomicrographs, jointly with those of Mr. La Manna, were ex- 

 hibited before the New York Mineralogical Club in April, 1911, and 

 again at the reception of the Brooklyn Institute's Department of Micros- 

 copy, March 9, 1912, and with additions in illustration of this paper. 

 (W. G-. Levison, Exhibit at the Annual Eeception of the Department 

 of Microscopy of the Brooklyn Institute, March 9, 1912.) 



In making these photomicrographs the writer used a lens with a small 

 stop giving a desirable depth of focus, a long bellows, a suitable color 

 screen, long exposure, reflecting screens to soften the shadows and a 

 very rigid adjustment of the apparatus and its supports. 



These autocolor plates have likewise afforded the -writer very satis- 

 factory lantern slides of colored cabinet specimens. Each picture ob- 

 tained is a direct positive. Such positives may afford approximately 

 similar copies by the camera or other color plates, but duplicates made 

 directly from the specimen are preferable. They may also, like any 

 colored transparencies, be copied by contact on approximately similar 

 colors, on a paper called Tto color paper by Dr. J. H. Smith, recently 

 introduced from Paris. 



