34 Hayes and Troivhridge — Irregularities in 



perature variation, corresponds to 41,608,000 at 26°, the mean 

 temperature of my experiments. Rowland's value at 26° is 

 41,720,000. Combining the mean of these, 41,664,000, with 



my result, I find 1 B. A. unit= . ',.„„' = '9904 earth-quad- 

 J 42,068,000 ^ 



rants per second. 



This research cannot compare in weight with the elaborate 



determinations of the ohm by direct methods, which have been 



made in England and this country since the conclusion of my 



experiments, but as few results by this method are at hand, I 



publish it as a slight contribution to the history of this vexed 



subject. 



Marlborough, N. Y., April 15, 1885. 



Akt. IV. — Cause of Irregularities in the Action of Galvanic 

 Batteries; by Hammond Vinton Hayes and John Trow- 

 bridge. 



In the May No. of this Journal, 1885, is described an apparatus 

 devised by Prof. John Trowbridge, for photographing the de- 

 flections of a galvanometer needle. A spot of light is reflected 

 from the mirror of a galvanometer, and from a fixed mirror, on 

 to a sheet of sensitive paper. When no current passes, the two 

 spots of light coincide; when the mirror is deflected, one spot 

 marks the zero of the scale ; the distance between the two spots 

 shows the amount the mirror has been deflected. In this way 

 all variations of current are accurately registered. We have 

 tested a number of batteries in this way, and have found that 

 in some cases the current was comparatively constant, or if any 

 variation occurred, it was of the nature of a gradual and regu- 

 lar fall. Examples of this action are to be seen in figures 1, 2- 

 and 3. In other cases the action was exceedingly irregular; 

 not only were there many marked variations in the strength of 

 the current, but these variations were made up of a multitude 

 of minor fluctuations. Both of these actions can be observed 

 in figures 4 and 5. The variations in some cases are as great 

 as twenty or thirty per cent of the total strength of the current. 

 It seems, therefore, of interest to find to what causes these 

 changes may be assigned, especially as such variations would 

 seriously affect delicate experiments. Moreover, in batteries 

 used for incandescent lighting it is absolutely necessary to ob- 

 viate this difficulty. 



It was observed that batteries without a porous partition 

 were not subject to these fluctuations. Such batteries as the 

 Leclanche' exhibit smooth unserrated curves, whereas all bat- 



