120 



THE AMEKICAN MONTHLY 



[June, 1880. 



An interesting exhibition of the per- 

 formance of a Spencer's " Professional " 

 one-quarter and one-sixth inch and a 

 Gundlach one-quarter inch objective on 

 the MoUers, balsam test plate was then 

 given. 



M. Virginia Smith, Cor. Sec. 



REVIEWS OF BOOKS. 



Microscopic Examination of Samples of 

 Commercial Arsenic, and the Practi- 

 cal Results to Which it Leads. By- 

 Edward S. Dana, Ph. D. Jersey City, 

 N. J. : F. D. Lynn & Co. (Pamphlet, 

 pp. 36. 50 cents.) 



Commercial arsenic occurs in two dis- 

 tinct varieties, viz.: as "glass-arsenic," 

 which is transparent and not crystalline ; 

 and as a white, ciystalline solid. The 

 ground arsenic of the shops is made by 

 passing either of these varieties between 

 millstones. Most of the arsenic used in 

 this country is manufactured in England, 

 where the crystalline variety is the most 

 usual product. 



Under the microscope the powdered 

 arsenic from the glassy variety is com- 

 posed of amorphous particles or dust, 

 with little or no appearance of crystalliza- 

 tion. On the other hand, the crystalline 

 variety, when ground, shows a great 

 abundance of perfect octahedral crystals, 

 sometimes mixed with more or less dust, 

 which partly comes from attrition and the 

 crushing of the large crystals. 



The pamphlet of Prof. Dana gives an 

 excellent description of the characters of 

 various kinds of arsenic, illustrated with 

 cuts of the four samples which attracted 

 so much attention during the Hayden 

 trial. 



We may give a very brief summary of 

 Prof. Dana's conclusions in the following 

 words : The form of the crystals is not 

 likely to be of much assistance in distin- 

 guishing different samples. The size, 

 however, is of great importance for this 

 purpose, in some samples the crystals 

 will be quite uniform in size, in others 

 they may vary widely. They may meas- 

 ure from ^j,ij^-inch to ^J-^-inch across. 

 The appearance of the surfaces, whether 

 they are bright or dull, when examined by 

 reflected light, often affords a means of 

 distinguishing specimens. The relative 

 amount of dust and crystals should be 

 observed. According to the experience 

 of Prof. Dana, arsenic does not seem to 

 be very much adulterated. 



Exchanges. 



[Exchanges are inserted in this column without 

 charge. They will be strictly limited to mounted 

 objects, and material for mounting.] 

 Polyzoa, Palates of MoUusca, Foraminifera, Sponge 

 and Holothurian-Spicules, Synapta-Anchors, Chirod- 

 ota- Wheels, Echinus-Spines, Minute Sea Shells, in ex- 

 change for Polyzoa, Foraminifera, Histological and 

 Pathological preparations, etc. Also, a quantity of 

 Sea Shells in exchange for Land and Fresh-Water 

 Shells. 



F. M. HAMLIN, M. D., Auburn, N. Y. 



J. J. B. Hatfield, Arsenal Avenue, Indianapolis, 

 Indiana, will exchange Bleached Plant-Sections for 

 good Diatomaceous material. List furnished on ap- 

 plication. 



Pleurosigmas and other unmounted Diatoms, both 

 Fresh Water and Marine ; also Marine Algae, Ferns, 

 and a_ large quantity of miscellaneous microscopical 

 material in exchange for good mounted objects. 



M. A. BOOTH, Longmeadow, Mass. 



To exchange, well-mounted Slides of Hair for 

 mounted or unmounted specimens of hair from the 

 rarer animals ; lists exchanged. WM. HOSKINS, 



208 S. Halsted street, Chicago, IlL 



Nicely mounted Slides (opaque) of the Coal-tar 

 Derivatives, chemically prepared, crystalline in form, 

 showing their beautiful colors, in exchange for other 

 well-mounted material. Chemical name and formula 

 attached to each Slide. About a dozen varieties on 

 hand. F. L. BARDEEN, M.D., 



30}^ Meigs street, Rochester, N.Y. 



Vanadate of Ammonia, (N H*) ^ V O *, Slides for 

 the Polariscope in exchange for other Slides. 



H. POOLE, Practical School, Buffalo, N. Y. 



Slides mounted from injected Frog's Gall-bladder, 

 Liver, Kidney, Stomach, Intestine and other parts, 

 exchanged for other good and interesting prepa- 

 rations. C. BLASDALE, M. D., 



Jericho, Queens Co., N. Y. 



Well-mounted, selected and arranged Diatoms, for 

 good histological, pathological or anatomical prepara- 

 tion. State what you have, and terms of exchange. 

 W. W. RINER, Greene, Iowa. 



Foraminifera from Sl)onge-sand, Marl-sand, and 

 Chalk ; Transparent Prisms of Carbonate of Lime 

 from fossil Shells ; Fresh and Salt Water Diatoma- 

 ceous material ; Carapaces of Rhizopods ; polished 

 sections of Fossiliferous Limestones, Corals, etc., to 

 exchange for any microscopical material. 



K. M. CUNNINGHAM, 

 Box 874, Mobile, Ala. 



The American Monthly Micro- 

 scopical Journal. 



Issued on or before the fifteenth 

 day of each month. 



Correspondence should be ad- 

 dressed to the Editor, Romyn Hitch- 

 cock, 53 Maiden Lane, New York. 



Terms : $1.00 per year ; single 

 numbers, 15c. To foreign subscrib- 

 ers, 6^ francs, or 5 shillings sterling. 



