624 
MESSRS. R. T. GLAZEBROOK AND S. SKINNER ON THE 
and filtration was employed, is most closely in agreement with our standard, and this 
agreement was attained immediately after the cells were set up. It will he noticed, 
however, that the ceils, Nos. 155-157, in which the old paste was used, are too low 
by about ’0008 volt, though they agree well together. 
§ 32. Professor Ayrton’s Standards. 
By the kindness of Professor Ayrton we have been able to compare two cells set 
up Dr. Mujrh ead, and used as standards at the Central Institute, with ours. These 
two cells have a thermometer sealed into the case which contains them. This case 
was packed in sawdust, and one of our own thermometers verified at Kew last 
November was placed in the sawdust. The thermometer in the cell was found on 
some five or six different occasions to read 0 o, 4 or 0°"5 below our own. The Kew 
correction for our standard is — 0°T6, at about 16°, the temperature of the obser¬ 
vations. According to this there is a correction of about + 0 o- 3 required to the 
thermometer in the cell. 
Making this correction, the following values were found for the excess of E.M.F. of 
Professor Ayrton’s cell over our own reduced to the same temperature :— 
Table XX. 
Cells. 
July 13. 
July 14. 
July 21. 
Number. 
1 
- 1-5 
0 
— 2 
2 
•5 
1 
- 1 
The differences, it will be seen, are within the errors arising from uncertainty of 
temperature. 
§ 33. Cells set up by Dr. Kahle in Berlin. 
In July last four cells were brought to Cambridge from Berlin, by Dr. Lindeck. 
Two of these, Nos. 69 and 70, were cells of the pattern devised by Dr. Beussner and 
described by Dr. Kahle, ( £ Electrotechnische Zeitschrift,’ July 22, 1892.) 
The positive pole is a piece of amalgamated platinum sheet. This and the mer¬ 
curous sulphate are contained in a porous pot. The outer vessel surrounding the 
porous pot contains saturated zinc sulphate solution and crystals of zinc sulphate. 
The negative pole is a rod of solid zinc amalgam, bent at right angles so that one 
part is vertical, the other horizontal. The vertical portion is surrounded by a tightly 
fitting tube of glass, the horizontal part is among the crystals, so that the effective 
portion of the zinc is always surrounded by saturated liquid. 
The other two cells, Nos. 29 and 12, are H cells, of the form devised by Lord 
