MA GNETIC REGISTRA TION. 1 77 



conclusion that there is no such thing as a perfectly continuous 

 uniform electric current. There is what appears to be a continuous 

 flow, but at certain periods this flow is very much increased ; and I 

 think that the more we experiment the more we shall see that the 

 electric current passing through any medium metallic wires and 

 other solids, fluids, or gases does take up certain pulsations, and 

 there is a maximum and a minimum of transmission there are starts 

 as it were in the current. Mr. Spottiswoode has been pursuing for a 

 long time some most interesting experiments on electric discharges in 

 vacuo. A portion of his researches was communicated the other day 

 to the Royal Society, and I and Dr. Miiller had the honour of com- 

 municating one with him, in which we believe we detected that when 

 stratification took place in vacuum tubes there was a fluctuation of the 

 current. We are still pursuing our experiments, and he is pursuing 

 his, and they all go to confirm that which Professor Blaserna has 

 stated. Professor Blaserna wishes me to say also, that Sir William 

 Thomson mentioned to him that, on mathematical grounds, he con- 

 sidered it was quite possible in fact probable that there were 

 oscillations in the electric current. 



MAGNETIC REGISTRATION. 



Mr. BROOKE, M.A., F.RS. : The subject to which I am desirous of 

 directing your attention is that of the instruments connected with the 

 automatic registration of the variations of the magnetometers, which 

 are exhibited in this building. In order that it should be better 

 understood by those who have not paid any particular attention to the 

 subject of magnetism, I may state that the magnetometers are in- 

 struments which have now for many years past been subjected to con- 

 tinuous registration by the photographic method, and those I may 

 briefly describe are three in number. The first is the declinometer, 

 a magnet suspended by a single skein, which takes up its position 

 according to the direction in which the magnetism of the earth 

 acts upon it, and if the direction of the action of the earth's mag- 

 netism varies, it will vary the position of this magnet, just the 

 same as it would that of a compass needle : the declinometer is 



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