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INFLUENCE OF A MAGNETIC FIELD UPON THE SPARK SPECTR.\ OF IRON AND TITANIUM. 



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the binding posts, the screw tops of the latter projecting from the oil to receive the wires connecting them 

 in any desired combination to the discharge circuit, so that the whole or any part of the condenser may 

 be used. An adjustable spark-gap between the nearer binding posts on each side protects the condenser 

 against too long a spark in the circuit which might cause the glass to be punctured. Connecting wires 

 from the two central binding posts are inclosed in thick glass tubes which pass through a second fiber 

 plate directly above the first and level with the top of. the tank to the high tension wires supported b}' 

 glass insulators and extending across the laboratory below the ceihng. A wooden cover fits into the top 

 of the tank and protects all parts of the condenser from dust. The leads from the transformer pass to 

 the overhead wires and other leads drop down to any piece of apparatus under the wires, so that the 

 heavy condenser can remain permanently in its place. 



In addition to the condenser, the circuit from the transformer contains a self-induction spool and 

 spark gap in series with the spark under observation. Several self-induction coils are available, but the 

 one regularly used consists of 207 turns of insulated copper 

 wire wound on a wooden cyUnder 132 cm long and 13 cm 

 in diameter. A sUding contact may be moved to any point 

 along the spool so as to include any desired portion of the 

 self-induction. 



The terminals for the spark on which the magnetic 

 field acts require different handUng according as the sub- 

 stance under examination is magnetic or not. In the 

 experiments with titanium, small pieces of the substance 

 known as "cast titanium," obtained from Eimer and 

 Amend of New York, were held in small brass clamps, the 

 vertical rods of which passed through larger horizontal 

 brass pieces set in a thick piece of fiber, through the 

 middle of which a brass rod passed and fitted into a 

 clamp, movable up and down on a support attached to 

 the base of the electro-magnet. 



When iron terminals were used it was necessary that 

 they be held rigidly in place on account of the attraction 

 of the magnet. In all cases small cylinders of Norway 

 iron were screwed on the end of brass rods. The size of 

 the iron tips varied somewhat according to the kind of 

 spark desired and the width of the magnetic gap used. 



Those most generally used with a strong field were 3.5 mm in diameter and about 10 mm long. In the 

 earher work the iron-tipped brass rods were held in a hard-wood frame composed of two vertical rings 

 held apart by four horizontal pieces. The wooden rings fitted over the magnet core, against the face of 

 each coil, while the brass rods passed with some friction through two of the horizontal wood pieces at 

 opposite ends of the diameter of the rings. A better holder for iron terminals was devised later. This is 

 shown in Fig. i and is a modification of that used for non-magnetic substances, the parts being much 

 more rigid. The rod of 6 mm diameter to which the iron tip is screwed passes through a square brass 

 rod 16 mm in thickness, having a saw-cut from the hole out to the end. A screw at right angles to this 

 saw-cut, worked with a bar, serves to clamp the rod so firmly that the magnet does not move it. As 

 the column supporting the holder is screwed to the base of the magnet, all parts could be clamped so 

 firmly that the iron tips were held exactly in place. 



The spark length for both iron and titanium was usually short on account of the proximity of the 

 magnet poles and the tendency of the spark to jump to these. With iron terminals, particles were given 



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