22 Frof. Thompson and Dr. Lodge on Unilateral 



taincd, was the same after the series of experiments as before. 

 The same weight of mercury (221 grms.) "was employed 

 throughout. The source of heat (the steam) was applied 

 below the crystal in every case. The original temperature of 

 the mercury having been read off on the thermometer, the 

 heat was applied until the temperature rose through a given 

 range — in the first experiment 50 degrees C, in the subsequent 

 ones 40 degrees C. Mercury was employed as being more 

 convenient in several ways, though a water calorimeter would 

 probably be more accurate. The results of nineteen experi- 

 ments, arranged in two series, are appended in a tabular form.. 

 In this Table the faces of the crystal-slice are denominated a 

 and /3. It was found by experiment that the face ft corre- 

 sponded to the analogous, a to the antilogous pole of the ori- 

 ginal crystal. 



Experinient- 



Eange. 

 T t 



Time occupied and 

 direction of flow. 



Time-ratio. 



Initial 

 temperatures. 



Which 

 operation 







atojB. 



/3 to «. 





C. 



first. 







m s 



m s 









I., II. 



50 



3 30 



5 



100 : 142 



19 and 22 



j3 to a 



III., IV. 



50 



4 15 



6 



100 : 141 



22-25,, 23 



j3 „ « 



V., VI. 



50 



3 40 



3 30 



100 : 945 



15-5 „ 20 



P „ « 



VII. 



Accident .... water boiled away. 







VIII., IX. 



40 1 2 30 I 3 00 1 100 : 120 



17-5 „ 21-25 



cc „ (3 



X., XI. 



40 | 2 30 1 2 40 100 : 107 



18-75,, 19*5 



a „ (3 





Crystal then reversed between tubes. 





I'., II'. 



Accidental escape of steam around calorimeter. 





III., IV. 



40 



2 45 1 3 15 



100 : 118 125-5 „ 27 



P „ « 



V, VI. 



40 



3 00 3 25 



100 : 108-3 22-5 „ 26-25 



* ., /3 



VII., VIII. 



40 



2 35 3 25 



100 : 125 24-75 „ 26-25 



• „/3 





Mean time-ratio | 100 : 119 







|(«toj8)(j8to«) 





It would appear therefore, by this method of experiment, 

 that the ratio of the two conductivities in opposite directions 

 through the crystal while it was becoming hotter was roughly 

 as 100 to 119. The more rapid flow is toward that pole 

 which, when the crystal is wanned, becomes positively elec- 

 trical. 



Electrical Conductivity. 



It only remains to add, that the second-named of the authors 

 has made a few preliminary experiments with the view of de- 

 tecting any unilateral conductivity of tourmaline for electricity. 

 These experiments were made with the same slice of tourma- 

 line, u B," as had been employed in the last-mentioned heat 

 experiments — a crystal in which the faces were normal to the 



