234 



MR J. C. BEATTIE ON THE 



We see that a still stronger field is now required to make the transverse effect vanish ; 

 and for the maximum negative effect also a stronger field is necessary than in the former 

 cases. 



Finally, the plate was again hammered, and the following results obtained : — 



Field Strength. 



Transverse Effect. 



Sign. 



Rotatory Coefficient. 



50-0 



023289 





2-5 



70-0 



016731 



- 



1-28 



100-0 



0-01837 



- 



0-098 



1056 



0-02256 



+ 



0-115 



123-5 



0-11556 



+ 



0-502 



1430 



0-21119 



+ 



0-79 



which again shows a considerable increase in the field necessary to reverse the direction 

 of the transverse current. 



The reversal of direction was not observed in Plates II. and III., nor was a maximum 

 effect reached in these two plates : In Plate I., again, no reversal was found, but a maximum 

 effect was reached with a field strength a little over 100. 



Another series of plates was now made from a new supply of mercantile bismuth. 

 Two Plates, VIII. and IX., were made each about 3 mm. thick ; VIII. was cooled quickly, 

 IX. slowly. The transverse effect was negative throughout ; it reached a maximum in 

 both cases, and then began to decrease ; but it could not be made to vanish by field 

 strengths at disposal. 



Two other Plates, X. and XL, were made, each about 1*5 mm. thick; X. was 

 cooled quickly, XI. slowly. In these two plates the transverse current vanished, and 

 with higher fields had the opposite sign positive. 



Another Plate, XII., was made in the form of a cross ; to the two arms of the cross 

 the galvanometer wires were soldered, and the effect of the soldering on the plate as a 

 whole minimised. (Cp. fig. E.) With this plate the following results were obtained: — 



Plate XII. 



Length, 

 Breadth, 

 Thickness, 



6-22 

 1-85 

 0-10462 



Field Strength. 



Transverse Effect. 



Sign. 



Rotatory Coefficient. 



25-2 



0-17158 





5-74 



34-6 



0-18389 



— 



4-48 



45-5 



018115 



— 



3-36 



88-3 



0-05617 



- 



0-538 



1030 



0-0119 



+ 



0-097 



116-5 



006051 



+ 



0-438 



137 



0-16766 



+ 



1033 



145-0 



0-20602 



+ 



1199 



