308 MM. Oumoff and Samoiloff on Electric 



which indicates that the mutual induction is nine-tenths of 

 the value it would have in the case of no magnetic leakage. 

 The coefficient of magnetic leakage is accordingly found to be 

 10 per cent. ; thus : — 



f=l-0-9 = 0\L0. 



Fig. 7 is drawn to represent the values of the various elec- 

 tromotive forces in the primary circuit of a transformer, for 

 a given value of the primary current and for different values 

 of the secondary resistance. If the magnitude of each line is 

 divided by the primary current I„ fig. 7 represents the 

 values for the primary impedance (without any assumption 

 as to constant current or electromotive force) for different 

 values of the secondary resistance. The effect of magnetic 

 leakage upon the primary impedance of any transformer is 

 thus shown for different values of the secondary resistance. 



The above construction affords a simple method of studying 

 the conditions for a decrease of the primary impedance of a 

 transformer when the secondary circuit is closed*. 



Curves corresponding to the dotted curve in fig. 7 have 

 been experimentally determined f by the writer. 



Cornell University, May 1896. 



XXXIII. Electric Images in the Field of a Hittorfs ( Crookes* ) 

 Tube. By N. Oumoff and A. Samoiloff|. 



THE influence exercised by a Hittorfs tube on electrified 

 bodies shows that the electric field created in the interior 

 of the tube extends also to the exterior. Evidently the 

 objects brought into this field, whether to explore its elec- 

 trical properties or, as in the experiments of Lenard and 

 Bontgen, to produce or to receive shadows acquire a new 

 electrical condition and by their presence modify the primi- 

 tive field. It is impossible to estimate a priori this modifi- 

 cation and the part it plays in the production of the pheno- 

 mena observed. In investigating these questions we finally 

 adopted an experimental method intended to furnish us with 

 the means of forming a general idea of the electrical pro- 

 perties of the field of a Hittorfs tube and the modifications 

 which it undergoes. 



* Discussed at length before the Physical Society by Mr. E. C. 

 Rimington in his paper "On Air-core Transformers," Philosophical 

 Magazine, vol. xxxvii. p. 394. 



t 'Proceedings of the International Electrical Congress,' Chicago. 

 1893, p. 234. 



X Communicated by Lord Kelvin, F.R.S. 



