544 



Mr. Seibei Konno on the Variation of 



cylindrical cavity 5 mm. high and 20 mm. wide, in which 

 a small, flat heating-coil is placed. On each side of the 

 cavity two narrow holes a, b and c, d, each 1 mm. wide 

 and 11 mm. deep, are radially bored at a distance of one 

 centimetre to receive the two junctions of a differential 

 thermocouple, which measures the temperature-gradient 

 along the axis of the cylinder. The two thermocouples 

 consist of iron and nickel wires in the case of the investi- 

 gation of the metals having relatively low melting-points ; 

 but in the case of aluminium and antimony, iron wire is 

 replaced by a platinum wire to avoid the disturbance caused 

 by an abnormal change of thermoelectromotive force due 

 Fig. 1. 



Fiff. 2. 



Ph 



Pt; 



Pt 



to the A 2 transformation of iron, e, f is a duplex thermo- 

 couple, consisting of platinum and platinum-rhodium wires, 

 by which the temperature-gradient in the specimen C, and 

 at the same time that of the specimen at point f, can be 

 measured. Its connexion is shown in fig. 2. The two 

 junctions e, f are coated with thin asbestos paper in such 

 a way that the insulation between the junctions and the 

 specimen, both in the solid and liquid states, is perfect, the 

 horizontal portions of the wires being protected by thin 

 porcelain tubes. Its cold junction is placed in a water- 

 bath, whose temperature is read by a thermometer. B, is 

 a thick porcelain tube, and the interspace between the tube 

 and the steel pieces JB and I) is tightly packed with caolin 

 kit. The two junctions <?, / go out through the wall of the 

 tube, and are so firmly fixed to it that the distance between 



