OF AKTS AND SCIENCES : MARCH 28, 1865. 



481 



friend, Mr. A. E. Verrill, assistant in the Museum of Comparative 

 Zoology, to whom I am indebted for the photographs from which the 

 plate was taken, and who, in the midst of pressing occupations, has 

 accomplished for me what professional photographists would not 

 undertake. 



List of Substances experimented upon. 



Baryta, 



Strontia, ... 



Lime 



Magnesia, 



Alumina, 



Glucina, ... 



Zirconia, 



Zinc, Oxide of. 



Cadmium, Oxide of, . 



Lead, " " . 



Bismuth, Teroxide of, . 



Antimony, " " 



Arsenic (Arsenious Acid) 



Niobic Acid 

 Selenium 



(BaO 



(SrO 



(CaO 



(MgO 



(AI2O3 



(GI2 Os 



(Zr, O3 

 (Zn O 

 (Cd 

 (PbO 

 (BiOa 



(SbO, 

 (ASO3 



Supplement. 



(Nbj O3) 1 Tellurium 



I Cerium, Protoxide of. 



(CeO) 



Baryta. — Baryta is dissolved in borax in large quantities before 

 a precipitate is obtained.* When carefully flamed, opaque, milk-white 

 crystals of a hexagonal, and also of an hourglass shape, are formed 

 (see Plate, Figs. 1 and 2), often distinctly visible even to the naked 

 eye. There are likewise, sometimes, aggregations of rectangular crys- 

 tals. In what corresponds to the terminal, or basal planes of the 

 hourglass-shaped crystal, a hexagonal outline may be observed in the 

 one delineated in the plate (see Fig. 2) ; but, rarely having obtained 

 so large and perfect crystals of this form as the one photographed, I 

 am unable to say how constant this feature may be. 



With microcosmic salt, slight flaming produces beautiful hexagonal, 

 stellate crystals, not opaque, at least in their inception, and exhibiting 

 a structure resembling some of the commonly depicted forms of snow- 

 flake crystals. Accompanying these I have noticed a rectangular 



* As a matter of convenience, I use the term "precipitate" to designate the 

 crystalline or other aggregation, produced by the flaming process within or upon 

 the surface of the bead. 



