CENTRAL SCIENTIFIC CO., CHICAGO, U. S. A. 



205 



Removable 

 Coil System. 



No. F4453. 



ELECTRICAL INSTRUMENTS, ALL KINDS 



BATTERIES, Primary and Storage, see general heading Batteries. 



BELLS, Electric, see general heading Bells. 



CONDENSERS, Paper and Mica, see Catalog F of Physical Apparatus. 



DEMONSTRATION ELECTRICAL APPARATUS, see Catalog F of Physical Apparatus. 



ELECTROLYSIS OF WATER APPARATUS, see Lecture Apparatus. 



ELECTROLYTIC APPARATUS, see Xo. 5140. 

 F3609. ELECTROMAGNET, 5 ohm resistance, for instrument making $1.00 



ELECTROSCOPES, see Radioactivity Apparatus. 



ELECTROSTATIC APPARATUS, see Catalog F of Physical Apparatus. 



FURNACES, see general heading Furnaces. 



F4453. GALVANOMETER, D'Arsonval, Wall Form. This Galvanometer is a superior instrument, com- 

 pact in design, and well finished in every detail. 



The Magnet is laminated, giving a strong, uniform and permanent field, which is concentrated by 

 a soft iron core. The instrument is mounted on a finely finished hardwood board. 



Coil System. As noticed from the illustration, one of the principal features of this Galvanometer 

 is its REMOVABLE COIL SYSTEM. The coil is suspended in a frame and forms with it a 

 I'NIT which slides into place by means of guides into a good electrical contact. It is there- 

 fore posible, by securing any number of coil systems, to have a universal instrument with only 

 the additional' cost of the extra systems. Also, if any adjustments or repairs are to be made 

 on the suspension system, the frame can be removed and laid flat on the table. 



Each Galvanometer is supplied with a 250 ohm DEAD BEAT Coil, with a plane mirror of %-ineh 

 diameter. Extra Coils, Dead Beat and Ballistic, are listed below. 



The Suspension. The upper suspension, unless otherwise requested, is a steel ribbon (see No. 

 F4515), which has a high tensile strength and a zero set of less than a millimeter. The sensi- 

 bility can be much increased by the substitution of phosphor-bronze suspension. 



The Reading Device consists of a telescope with achromatic objective and a biekrome scale 

 mounted upon an adjustable arm, which may be entirely removed when not in use. 



The Housing is of cast aluminum, combining strength with lightness, and is detachable by 

 loosening two thumb screws, giving easy access to the interior. A large window is provided 

 for viewing the moving system. 



Mounting and Leveling. The galvanometer is suspended on the wall by means of two suspension 

 loops on the hardwood board which supports the magnet and housing. These loops are pro- 

 vided with leveling screws and, with a third leveling screw in the center of the base board, 

 provide a convenient means of leveling the instrument. 



Sensibility. From the mean of a number of readings the sensibility in megohms was found to 

 be as follows: 



With dead beat coil of resistance, ohms 5 250 500 



At working distance 3.5 33 48 



At one meter distance 7.3 68 100 



Complete with 250 ohm Dead Beat coil, and jeweler 'a screwdriver 35.00 



