1884.] DanielVs Cell of very small Internal Resistance. 175 



rope, terminated with two thick slips of copper which are fastened 

 together mechanically, but electrically insulated, and form the flat 

 duck's-bill shaped piece II, shown in section, fig. 3. The electrodes of 

 any instrument which is to be connected with the cell may be also 

 terminated with two copper slips, which are pushed on over the piece 

 ZZ and held on by india-rubber bands. 



The mode of supplying the cell with sulphate of copper still remains 

 to be described, and it is this which constitutes its most important 

 peculiarity. The liquid contained ordinarily in the tray Daniells is 

 somewhat dilute solution of sulphate of zinc (sp. gr. 1'12 to 1*14), 

 the lowest layer of which is saturated with sulphate of copper. The 

 sulphate of zinc solution is kept at the proper density by occasionally 

 drawing off quantities of strong liquor and replacing by pure water, 

 testing by a hydrometer or with specific gravity beads. The sulphate 

 of copper is supplied by dropping a proper quantity of blue vitriol in 

 crystals into the cell round the edges. This is sufficiently easy when 

 the cells are of moderate dimensions, and where a large number of 

 them is being constantly used and regularly attended to in a business- 

 like way, as at a telegraph station. When, however, the size of the 

 tray is very large, and when the cell is being used intermittently, this 

 simple method becomes difficult and unsatisfactory ; and, owing to 

 want of uniformity of the solutions, the cell is rarely obtained in such 

 a condition as to be ready to give the results which ought to be 

 expected from it. The copper sulphate supplied in crystals does not 

 dissolve sufficiently quickly and spread itself over the whole surface 

 of the lower plate, and difficulties arise as to the dilution of the 

 sulphate of zinc without stirring up from the bottom remnants of 

 unused sulphate of copper. 



To avoid these troubles, and to make the starting and stopping of 

 the action of the cell easy and rapid, I have arranged to supply the 

 sulphate of copper in the state of solution, and to deliver and to 

 remove it very gently but very quickly, and also simultaneously, at 

 many parts of the bottom of the cell. 



X and Y are two earthenware tubs placed one on either side of 

 the cell ; and it should here be remarked that the cell is raised up from 

 the floor on common building bricks. From these vessels a number 

 of siphons or delivering tubes, t, t, t, of which ten* are shown in the 

 diagram, proceed to different parts of the cell. The tubes are of 

 thin glass, except the bend ss, which is of flexible india-rubber 

 tubing, and enables the extremities to be taken with ease out of the 

 vessels X and Y for clearance or for starting of the siphons. The 

 tubes are held in position by passing through holes in the boards w, w, 

 and the glass portions are bent in a gas flame to the proper shape for 



* I have recently doubled the number with great advantage. 



