46o SECTIONAL TRANSACTIONS.— G. 



Short Papers by junior engineers (12.0). 



Mr. G. C. EccLES. — A moving coil vibrometer. 



Afternoon. 

 Visits to — 



(a) Works of Messrs. Chivers & Sons, Histon. 



(b) Model of Ouse Catchment Board. 



Monday, August 22. 



Major F. C. Cook. — Road development in Great Britain (10. o). 



Prof. F. C. Lea. — A torque converter for motor cars (ii.o). 



Short Papers by junior engineers (12.0). 



Mr. C. H. Edgecombe. — The braking of railway trains and some tests 

 made to determine the coefficient of friction under various conditions. 



Mr. D. M. Wilcox. — The calculation of train running times. 



(concurrently with the above session.) 



Joint Discussion with Section A (Mathematics and Physics) on Magnetic 

 measurements with special reference to incremental conditions (lo.o). 



Chairman : Prof. W. Cramp. 



Prof. W. Cramp. — The position regarding incremental measurements. 



Mr. C. E. Webb. — Recent improvements in soft magnetic materials. 



Mr. D. C. Gall. — Instruments suitable for incremental magnetic 

 measurements. 



The paper deals with the instruments and circuits suitable for the 

 measurement of incremental permeability upon rings and cores at low 

 degrees of alternating modulation. 



Dr. L. G. A. Sims and Mr. J. Spinks. — The place of ballistic measure- 

 ments in incremental magnetism. 



The paper draws attention to the possible adaptation of the classic 

 ballistic measurement to routine incremental magnetic testing. It is proved 

 experimentally that very close agreement occurs between ballistic and 

 alternating current measurements so long as a low frequency sine wave of 

 current is used in the alternating current case. The paper shows further 

 that either for ring samples or for transformer core assemblies there is a 

 considerable range of superimposed inductions over which general agree- 

 ment between all methods of measurement, including the ballistic method, 

 can be relied upon, so long as the alternating current tests relate to silicon , 

 steels and to low frequencies. The ballistic measurement is convenient 

 for adjusting circuit conditions to give stated degrees of modulation of the 

 polarisations, and this has been used in the paper to establish values of 



