116 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
Supplement. 
February 11, 1878. 
On January 1st, 1878, we charged up with liquid the 2960 cells we had been 
preparing during the four previous months ; 1500 of these were rod cells, and 1460* 
powder cells. Before combining them with the 8040 cells already in use we had the 
latter thoroughly examined and defective elements renewed. Advantage was taken 
of the preparation of the new cells in order to ascertain whether the old ones had 
retained their initial electro-motive force ; this was done by means of the quadrant 
electrometer referred to in the footnote to page 104, one pole of each battery being 
connected to earth, the other to the induction plate of the electrometer, and the 
following numbers were obtained : — 
Battery. 
No. of cells. 
Scale division. 
No. 1. 
1080 powder. 
Deflection per cell=0T069, made up afresh with new liquid. 
2. 
1080 „ 
„ „ =0-1040. 
3. 
1080 
„ ,, =0-1099, made up afresh with new liquid. 
4. 
1200 rod 
„ „ =0T008, cells contained 6 - 8 per cent. ZnCl 2 . 
5. 
1200 „ 
„ „ =0-1046, 
6. 
1200 „ 
„ „ =0-1050, „ 
7. 
1200 „ 
„ „ =01063, „ „ 
8. 
1500 „ 
„ ,, =0-1110, new battery. 
9. 
1460 powder 
„ „ =0-1096, „ 
The sum of the deflections of all the batteries equals 1173 scale divisions; the 
mean deflection per cell of 8 and 9 was O'l 103, therefore o^Ti~o 3 := 10,640 cells of the 
potential of the new ones, that the whole 11,000 were equal to when the observation 
was made. 
It was found by direct experiment with several of the trays of 20 cells that the 
formation of ZnCl 2 lessened the potential of the battery, and that it could be restored 
by removing the old liquid and charging the cells with a fresh solution of chloride of 
ammonium in the ratio of 23 grms. to 1 litre of distilled water. 
In giving the following particulars of the measurements of the striking distances, 
it is necessary to state that as No. 8 battery contains 1500 cells and No. 9 battery 
1460 cells, by adding No. 8 and 8 and 9 to the old series of 8040, we obtain 9540 
and 11,000 cells respectively. It was not thought necessary to commence all the 
measurements afresh, as this would have occupied much time and uselessly wasted the 
life of the battery, so that we have contented ourselves with merely taking the striking 
distance of the 8040 cells, each time for the several forms of terminals, and then the 
additional striking distance for 9540 and 11,000 cells respectively. These additional 
lengths of spark we have added on to the several means obtained for 8040 cells, as 
* The powder cells will be used to renew any of those in batteries 1, 2, 3 which may become exhausted, 
and will be replaced by rod cells. 
