50 PROCEEDINGS OP THIO AMERICAN ACADEMY. 



Experiment (/). lu the final state of a prism similar to the one used 

 in the last experiment, 311.9 grams of ice were melted in 5340 seconds 

 when the temperatures of the thermal elements on the faces of Plate III. 

 were 66^.4 and 54°. 1. This corresponds to a conductivity of 0.00260. 

 Here again the last figure is in doubt. 



We had occasion to measure the absolute conductivity of only one 

 other of the 60 cm. s(juare plates bought at the same time as Plate III. 

 This was Plate I. The results of two experiments made on it were 

 0.002 G2 and 0.00259. The crown glass used b}^ Oddone had a con- 

 ductivity of 0.00245, that of Lees* a conductivity of 0.00243. 



We will next cite a single experiment to show how much the con- 

 ductivity of the particular kind of statuary marble that we used could be 

 changed by moistening the stone. 



Experiment (g). A prism was made up of three plates of glass, A, P, 

 and Q, and three dry slabs of statuary marble, C, D, and E, arranged in 

 the order P A Q ED C with thermal junctions between P and A, A and 

 Q, E and D, D and G. The temperatures indicated by the thermal 

 junctions when the prism had sensibly reached its final state were 84°. 6, 

 67°. 7, 38°. G, and 27°. 7. D was then well moistened with water, and 

 the experiment was then repeated. The temperatures were then 85°. 3, 

 70°. 5, 46°.0, and 38°. 1, so that the conductivity oi D had been increased 

 in the ratio of 1.21 to 1. 



Experiment (Ji). In order to form an idea of the amount of change 

 with the state of the weather of the conductivity of a piece of our Carrara 

 statuaiy marble, we made three comparisons on three different occasions 

 of the relative conductivities of a slab of it (0) 1.08 centimeters thick, 

 and a plate {A) of standard glass. Between the experiments, was left 

 in a room the windows of which were much of the time open. The results 

 were as follows : — 



Temperature of the warm side of the glass. 

 Temperature of the cool side of the glass, 

 Temperature of the warm side of the marble, 

 Temperature of the cool side of the marble, 

 Ratio of the conductivities of the marble and the glass, 1 .84 



Average conductivity of the slab O, 0.00509 



Another specimen of Carrara marble had a conductivity of 0.00501. 



* We have not yet seen the paper by Mr. Lees mentioned in the March, 1898, 

 number of the Beibliitter zii den Annalen der Physik und Cheniie. 



