294 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Figure 4, and the same method of alternating the hotter and cooler streams 

 was used here that was used in the test of the copper-iron junctions. 

 The difference of temperature of the streams in the calibration tests was 

 usually about 4° or 5° C. 



In the conductivity experiments proper, the usual difference of temper- 

 ature of the copper-German silver junctions, the usual difference of tem- 

 perature, that is, of the ingoing and outgoing water, was probably rather 

 more than 0°.5 C. 



The Flow of Water. 



The method of controlling and heating the streams of water was 

 essentially the same as that described in the previous paper,* and illus- 

 trated in Figure 5 of that paper. Powerful gas-burners, of a type 

 manufactured by the Buffalo Dental Comijany and expressly intended 

 for heating streams of water, were used. Each stream flowed through the 

 conduction apparatus from the base of an overflowing standpipe, which 

 device answered the double purpose of insuring a constant flow, and 

 allowing air bubbles to escajie from the water before reaching points 

 where they would do harm. A supplementary air-vent was provided 

 for the upper stream near its entrance at A, Figure 2. 



The stream which flowed above the disk, the only one upon which 

 careful measurements were made, ran into a covered barrel standing 

 upon a platform balance. The time of flow was noted, and the amount 

 of water accumulating in the barrel during that time was determined by 

 weighing. The rate of delivery of the stream ranged, during the whole 

 course of the investigation, from about 15 grams per second to about 

 25 grams per second. The stream flowing beneath the disk was of the 

 same order of magnitude. 



Results and Discussion. 



A (ew sets of observations were made at low temperatures without the 

 use of the jacket. A few others were made at various temperatures with 

 use of jacket, but without the cotton packing within and below it. These 

 observations were preliminary, and none of them will be used in dedu- 

 cing the final results. The detailed results of subsequent observations, 

 made with jacket and cotton packing in use, are given below in chrono- 

 logical order. None are omitted, although some are placed in brackets 

 for reasons to be given later. 



* Tliese Proceedings, Vol. XXXI., 1896. 



