654 REPOET--1892. 



isation to be gone through at any frequency up to twenty cycles per second without 

 causing any serious disturbance of the diagram to arise from the inertia of the 

 working parts, a continuous-current commutator being used to effect the reversals. 

 The general character of the diagram is the same at this speed as at any lower 

 speed. The presence of an air-gap in the magnetic circuit may be allowed for by 

 giving the diagram which shows the relation of magnetism to magnetising force a 

 shear backwards through such an angle as will compensate for the shearing effect 

 of the air-gap. This can be automatically done in the magnetic curve tracer by 

 placing the fixed point about which the mirror turns in such a position that the two 

 components of motion are inclined not at right angles at an angle which exceeds a 

 right angle by the amount of the shear that is required to rectify the diagram. 



4. On a Magnetic Balance and its Practical Use. 

 By Dr. H. E. J. G. du Bois. 



This instrument is intended to afford an easy and reliable means of determining 

 magnetic curves or hysteresis loops of materials used in machine construction. One 

 test-piece is cut to 15 cm. length, and by means of a template is best turned down 

 so as to have 1 cm.^ cross-section ; this obviates all further calculation. Its circuit 

 is completed by two end-pieces and a massive yoke, excentrically supported ; the 

 resulting moment is compensated by weights sliding on a divided horizontal scale, 

 on which the values of the magnetisation are directly read in absolute units. The 

 value of the magnetising field is given by multiplying the current in the coil into 

 ten. In plotting the results abscissae are measured from an ' instrumental direc- 

 trix,' inclined towards the left from the axis of ordinates. The apparatus was 

 exhibited to the Section, as well as half a dozen test-pieces, and the curves obtained 

 for them. 



5. Beport of the Gommittee on Electrical Standards.— See Reports, p. 132. 



6. On Wire Standards of Electrical Resistance. By Dr. St. Lindeck. 



See Reports, p. 139. 



7. On the ClarTc Cell. By Dr. K. Kahle. — See Reports, p. 147, 



8. A Discussion on the Nomenclature of Units w as opened hy 

 Professor Oliver J. Lodge, F.B.S. 



[In connection with this discussion a report on units was read by M. C. E. 

 Guillaume. This communication was ordered by the General Committee to be 

 printed in extenso.^See Reports, p. 165.] 



9. On the Dielectric of Condensers.^ By W. H, Preece, F.B.S. 



Artificial cables are very useful adjuncts to the laboratory of the telegraph 

 engineer. They not only enable him to experiment at his leisure, but they form 

 very useful means to test and compare high-speed and delicate telegraph apparatus, 

 and especially telephones. I have one, made some years ago, which has been in 

 incessant use, composed of fifty-four inductionless coils of insulated copper wire, 

 each giving 33 ohms' resistance, and having a condenser of one microfarad capacity 



' Lord Kelvin proposes to call this useful instrument a 'Leyden,' because the 

 term 'condenser' is applied to other more appropriate mechanical and physical 

 apparatus. 



