1892.] 



Number of Fellows elected into the Society. 



463 



the effective potential difference, as measured by a voltmeter, being 

 the same in the two cases. The induction, if there is no magnetic 

 leakage, will be 



— I = (Nj/Rtf) (5 cos 20 £ + 47 COS 600^ + 0-11 COS 1800 1), 



the term which was so insigni ficant, which had only l/800th of the 

 importance of the most important term in practically estimating the 

 volts, is now greater than what is usually taken to be the greatest 

 term when we come to deal with the actual induction. Magnetic 

 leakage will not much affect this condition of things, but it will 

 greatly diminish the importance of the higher harmonics. 



When experimenters say that they keep the primary volts constant, 

 they mean that they keep the effective primary volts constant. It is 

 obvious from the above considerations that different methods of 

 keeping effective volts constant will produce very different kinds of 

 induction. The effects produced by an exciting current in a choking 

 coil or unloaded transformer are evidently very complicated. Let the 

 dynamo have a perfectly pure simple harmonic law of electromotive 

 force ; we have seen that even when no hysteresis is assumed, the 

 current will possess large harmonics and the induction possesses cor- 

 responding harmonics. The energy wasted in the creation of these 

 harmonics may be called "hysteresis" loss, but it cannot be alto- 

 gether the same as the hysteresis loss in slowly-performed cycles of 

 magnetisation ; it will be different if the dynamo does not follow a 

 simple harmonic law in its electromotive force, and the apportioning 

 of the small higher harmonics to the primary voltage and to the in- 

 duction must greatly depend upon the self-induction of the dynamo 

 machine. 



II. " On the probable Effect of the Limitation of the Number 

 of Ordinary Fellows elected into the Royal Society to 

 Fifteen in each Year on the eventual total Number of 

 Fellows." By Lieut.-General R. Strachey, R.E., F.R.S. 

 Received April 13, 1892. 



The discussions that arose in connection with the revision of the 

 Statutes of the Royal Society during the years 1890 and 1891, led 

 me to endeavour to obtain definite data on which to found a trust- 

 worthy opinion as to the effect of the existing limitation of the 

 number of yearly admissions, on the eventual total strength of the 

 Society, and the probable result of increasing the number beyond 

 fifteen, the present limit. 



The. facts bearing on this subject, so far as I have been able to 



