902 Mr. C. W. Heaps on the Effect of 



The metals to be examined were arranged in different forms, 

 depending upon the field desired and the character of the 

 metal. Iron, nickel, and cadmium were drawn out into fine 

 wire, and for the strong fields of the electromagnet were 

 stuck with shellac in a zigzag fashion upon one side of a strip 

 of mica about 2 cm. square. This thin strip could then be 

 mounted on a brass plate, placed between the poles of the 

 electromagnet, and arranged to turn so that the direction of 

 the current in the zigzag wires could make any desired angle 

 with the magnetic field. 



For the small fields of the solenoid the same specimen 

 could be used without modification in measuring the effect of 

 a transverse field. It was simply mounted on the end of a 

 circular hard rubber block and lowered into the solenoid. 

 For longitudinal magnetization in these small fields the wires 

 were supported in a framework consisting of two circular 

 hard-rubber blocks — the blocks just fitting the inner tube 

 of the solenoid — held apart by three brass rods. The wires 

 were connected in series by soldering short copper wires of 

 negligible resistance across the ends. In cases where sagging 

 of the wires occurred the solenoid was set up vertically and 

 weights arranged so that the wires were kept taut. 



Manipulation of theHeusler alloy was much more difficult, 

 owing to the extreme hardness and brittleness of this substance. 

 The alloy was obtained from Kahlbaum, and came cast in the 

 form of blocks. A thin section was cut from a block with a 

 diamond saw and cemented to a glass plate. After being 

 ground thin, narrow strips were cut from the section by the 

 use of a small file, and these strips were mounted on mica or 

 glass in the desired position and soldered in series, after 

 having their ends plated with copper. The total resistance 

 thus secured was rather small, as it was not advisable to use 

 very many strips ; but the magnitude of the effect was so 

 great that no trouble arose from this source. 



The difficulties of the experiments arose chiefly from the 

 smallness of the effects to be measured. In spite of all pre- 

 cautions temperature changes affected the metals to a certain 

 extent. Usually after balance was secured the galvanometer 

 showed a slow and steady drift to the right or left, depending 

 upon whether the metal was growing colder or warmer. By 

 regulating the flow of water between the tubes of the solenoid 

 it was possible to check this drift, or at least the galvanometer 

 could be kept slowly vibrating between two limits. Then by 

 making observations each time the galvanometer came to the 

 same limit the effect of temperature changes was practically 

 eliminated. 



