356 ANNALS NEW YORE ACADEMY OF SCIENCES 



which time he would give a public lecture on the "Geology and Mineral 

 Eesources of Alaska." 



Dr. Hovey announced that the- seismograph which had been presented 

 to the Academy by Mr. Emerson McMillin had reached New York and 

 had been passed by the Custom House. 



The following programme was then offered: 



Wallace Goold Levison, Illustrations of Mineral Associations 



by Means oe Color Plate and other 

 Photographs of Opaque Specimens. 



A. B. Pacini, The Metamorphism of Portland Cement. 



II. 



Charles T. Kirk, Alterations in the Snake Eiver Basalts. 



(Read by title.) 



Summary of Papers. 



Mr. Levison said in abstract : On a previous occasion the writer pre- 

 sented to the Academy a "Note on Photographs of Minerals for illus- 

 trating Books, Papers and Lectures" (Annals N. Y. Acad. Sciences, 

 Vol. XII, pp. 661 and 663). The examples consisted of lantern slides 

 and prints of light-colored mineral specimens of cabinet size mounted 

 on standard size blocks with standard size labels and of microscopic 

 mounts in Eakestraws. (See "Report of Committee on Standard Sizes," 

 N. Y. Acad, of Sciences, 1894.) The writer found it difficult to obtain 

 satisfactory photographs of highly colored minerals in or on colored 

 matrices, as such associations .usually afford poor contrasts on ordinary 

 plates. 



To produce representations of colored minerals at that time hand- 

 painted or colored lantern slides or prints were the chief expedient. 



Some" time later the M. A. Seed Dry Plate Co. introduced its G. B. 

 P. R. (green, brown, purple and red) plates, which served better than 

 ordinary plates for lantern slides of certain colored minerals. Thus 

 malachite and prehnite looked well on the green, native copper on the 

 red and rusty or yellow-colored minerals such as the stilbite and cal- 

 cite from Upper Mt. Clair, 1ST. J., on the brown plates. The entire plate 

 was usually of a tint much similar to that of the specimen, but different 

 parts of the specimen usually developed in tints intermediate between 

 the four possible colors above mentioned, so that pictures on these plates 

 made desirable lantern slides. This method was not applicable to paper 

 prints. 



The recently introduced color plates of Lumiere, Jougla and Dufay 



