176 L. CASELLA'S CATALOGUE 



FIG. 2063. FIG. 2069. 



2059. MAHOGANY BOXES for pair 2-feet magnets . . each 2 $ 



2060. 18-inch. . . 029- 



2062. 12-inch. . . 019 



See also magnetic needles for ships No. 933. 



2063. Electro Magnet on Stand (fig. 2063), consisting of a bar of very soft iron bent 



in the form of a horse-shoe, and covered with insulated copper wire. If a 

 current from a galvanic battery, even a small one, be passed through it, an 

 intense magnetic power is produced, continuing only so long as the battery is 

 in contact . . , . . . . 14 O 



VOLTAIC OR GALVANIC APPARATUS, ETC, 



Voltaic instruments are employed to exhibit a peculiar form of electric influence, 

 obtained under particular circumstances by chemical action producing certain effects 

 on bodies not usually obtained in the ordinary course of electrical excitation, as 

 friction, etc., etc. 



Dan id Ps Constant Battery. This form of battery consists of a cylindrical copper 

 vessel, in which is placed a porous earthen tube, containing a rod or slip of 

 amalgamated zinc ; dilute sulphuric acid is put in the porous tube and a 

 saturated solution of sulphate of copper into the copper vessel . Where a long- 

 continued and uniform current is required this battery stands pre-eminent. 



2065. DANIELL'S BATTERIES, copper cylinders, 6 by 3 inches, 5s. ; 9 by 3f inches, 7s. 6d. ; 



12 by 4 inches .... . . 10 6 



2066. SETS OF DANIELL'S CONSTANT BATTEEIES, with copper cylinders 20 inch, by 3, 



in wooden frames. The compound circuit readily exhibits both the quantity 

 and intensity effects. Any number of batteries may be used as a set, but 

 Daniell preferred a series of ten. Ten batteries with suitable connexions in 

 wooden frame . . . . . . . 440 



2067. SETS OF DANIELL'S CONSTANT BATTEEIES, a compound circuit of six batteries 



6 inches high, complete with connexions on mahogany tray . 250 



