Passing Isothermally from Solid to Liquid. 5 



former (D) is 15 - 23 cin in diameter, l-300 cm thick, turned accu- 

 rately cylindrical and polished on its lower surface. Besides 

 the central hole r, it has two small eyelets, ss, placed symmet- 

 rically on the same diameter, by aid of which the plate may 

 be suspended, §8. Finally the junction m/ of the thermo-couple 

 mm'm is soldered to the top of this plate, the wires passing 

 through the tube in the bottom, GG 



The plate DD is supported on the upper polished plane 

 surface of EE, by three plate glass spacers t, t, 'l cm to '2 cm high, 

 and *2X'2 cm 2 square. EE is, of the same diameter as DD, 

 but only -6 cm thick. The sides of the box EE, of which EE is 

 the top, project upward to form a gutter ZZ, in which the 

 excess of charge is caught and may be siphoned off. In case 

 of undercoolecl liquids this gutter is absolutely essential, and I 

 found it advantageous to coat it with vulcanized rubber 

 deposited from solution. Rough surfaces induce premature 

 freezing. The box implants its three steel feet on plates of 

 brass (not shown), imbedded in the top of GG, thus securing 

 the necessary firmness of the conducting system. Finally the 

 junction n', of a second thermo-couple nn'n, identical in every 

 respect with mm'm, is soldered to the bottom surface of EE, 

 and after passing through a sealed tubulure V in the side of 

 EE, the wires pass out through UG. 



One of the tubes GG which admit and withdraw large 

 bulks of water, communicates through a massive three-way 

 stop cock HK, with the faucet of the hydrant. The tubulure 

 gg which nearly touches the bottom of E, discharges into a 

 small cistern with two tubulures A and p, and a thermometer, 

 q, here registers the temperature of the efflux through A. 



To introduce the charge, liquid thymol is carefully poured 

 in through r, by aid of a fine funnel tube. In case of copper 

 plates this rarely succeeds at ordinary temperatures. I heated 

 the plates during charging above the melting point of thymol, 

 and then allowed them to cool in the closed environment. 

 The charge is best frozen when quite cold and from the center 

 outward, by contact with a crystal, inserted through r. Allow- 

 ance must be made for the volume contraction, §14. In the 

 following work with solid thymol, the glass spaces t, t, were 

 left in place. I believe now that this is unfavorable to perfect 

 adhesion between the solid layer and the copper plates, even 

 though the cold plates were found to be thoroughly cemented 

 together. A better plan would be that of placing the spacers 

 near the edge, and of removing them as soon as a sufficient 

 amount of thymol has solidified to sustain the upper plate. 



6. TAermo-couple. — The thermo-couples m and n, of germ an 

 silver and copper, being identical both as regards metal and 

 dimensions, the temperatures of the upper or the lower plate 



