500 M. F. Braun on the 
was brazed ; it was closed below by an iron disk screwed on, 
to the inside of which a piece of platinum foil was soldered. 
The screw closed against the molten metal in which the iron 
tube plunged. A platinum wire was in contact with the 
platinum foil. This was melted through the closed lower end 
of a glass tube. The bottom of this was filled to a height of 
about 10 millim. with graphite. Lead wire was pushed slowly 
into the glass tube, which melted and formed a continuous 
connection from the molten to the solid lead. The solid lead 
wire conducts again to points at the temperature of the room. 
All the different conductors (iron, platinum, and graphite) were 
completely surrounded by the molten metal in the pipe-head, 
which stood some 4 centim. above the top of the graphite 
layer. We may therefore assume equality of temperature in 
all. This last-described arrangement was employed for the 
circuits PbSn and SnBi. 
7. I pass now to the results obtained. If we take the 
temperatures as abscissee and the electromotive forces as or- 
dinates, the following results are obtained. Most, if not all, 
the curves are not actually straight lines ; they are of such 
a form that the centre of curvature lies on the side of the 
curve turned away from the axis of abscisse, i. e. the electro- 
motive forces increase more rapidly than corresponds to 
proportionality with the temperature. Only the curve for 
NaHg, which is almost straight for a considerable distance, 
seems at higher temperatures to assume a curvature towards 
the other side. The thermoelectric force of this element is, 
however, so small that measurements with it offered special 
difficulties. KHg is almost a straight line, but possesses 
certain peculiarities (see below). | 
The curves are certainly not of the second degree, but of the 
third at least. Tait’s assumption that specific heat of elec- 
tricity is proportional to the. absolute temperature, which 
would lead to the equation to a parabola, therefore does not hold 
good for molten metais. I give here a few numbers from the 
curve for the element PbHg. It is of especial interest, on ac- 
count of the property of lead, not to give any Thomson-effect. 
The first column gives the temperature of the warmer point 
of contact in Centigrade degrees, the second the same reckoned 
from absolute zero. ‘The temperature of the other point of 
contact is throughout 20° C. The third column contains the 
electromotive force e in micro-volts. If e is a function of 0, 
represented by a curve of the second degree, then s ought to 
be a linear function of 9. The fourth column shows the 
