1058 SEC. 19. EDUCATIONAL APPLIANCES. 



4456. Holtz's Electrical Machine. 



Auxiliary apparatus : a. Lightning-tube, b. Lightning-plate. 

 c. Chime of bells, d. Dancing dolls, e. Contrivance for breaking 

 glass plates, f. Henley's discharging rod. g. Discharging rod, 

 with joint. 



4457. Pair of Concave Mirrors, brass, 16 inch diameter, 

 8 inch focal distance, on tripods, with contrivance for adjustment 

 and equipment for heat experiments. 



4458. Two Sectional Models of Steam-engines. 



4459. Model of a Screw Steamer. 



4460. Lever Pyrometer. 



W. J. Rohrbeck, J. F. Luhme $ Co., Berlin (Dr. H. Rohr- 

 beck). 



Chemistry. 



4461. Plattner's Assay-balance, for blow-pipe purposes, 

 in mahogany case, with 1 gr. weight, indicating T \j- milligr., with 

 weights. 



4462. Balance, on stand, according to Wackenroder, to 

 carry 20 gr., and indicating 1 mgr., &c. 



4463. Technical Balance, on stand, to carry 500 gr., and 

 indicating 5 mgr. 



4464. Mohr's Tare-balance, in mahogany scale case^with 

 brass column, bow-scales, and ebonite plates, to carry 1 kilo- 

 gramme, and indicating 1 centigr. 



4465. Scales, for weighing substances affecting metals, to 

 carry 250 gr., and indicating 5 mgr. 



4466. Complete Mohr's Balance, for determining the 

 specific weight of liquid and solid bodies. 



4467. Mohr's Balance, with one arm. 



4468. a. Exsiccator, according to Schrotter, consisting of 

 tubulated glass jar on a frosted glass plate, framed in wood, with 

 crucible stand, and chloride of calcium tube. 



4469. b. Exsiccator, according to Fresenius, consisting of 

 glass cylinder, &c. 



4470. c. Exsiccator, according to Fresenius, with frosted 

 glass plate. 



4471. d. Exsiccator, according to Luhme, with porcelain 

 vessel for sulphuric acid, and etagere. 



