226 C. C. Hutchins— Thermo- Electric 



The material used for the analysis was from a single large 

 crystal and it appeared to be perfectly pure. It had a pale 

 green color and moderately thick pieces were transparent. 

 The results of the analysis are as follows : 



Calculated for 



H 2 0. 











Calculated for 





Found. 



Ratio. 



4PbO 



. 2C0 2 . S0 3 . 



so 3 



7-33 



1 





7-53 



co 2 



8-14 



2-02 





8*29 



PbO 



82-44 



4'04 





82.49 



H 2 



1-68 



1-02 





1-69 



99-59 100-00 



These results show that the mineral has the formula 

 PbS0 4 . 2PbC0 3 . Pb(OH) 2 and corresponds to the composition 

 suggested by Groth, thus adding one more to the many cases 

 in which his remarkable acuteness has deduced a simplified 

 and correct formula from the more complicated results of pre- 

 vious investigations. 

 Sheffield Scientific School, New Haven, Conn., June, 1894. 



Art. XXXII. — Thermo- Electric Heights of Antimony and 

 Bismuth Alloys ; by C. C. Hutchins. 



The writer, being much interested in the preparation and 

 use of thermo-couples of very small mass, undertook the fol- 

 lowing experiments with a view to finding the best combina- 

 tion of elements for the purpose. 



Much study has been devoted to the subject already, chiefly 

 however for the production of thermopiles designed to replace 

 ordinary batteries. The extremely brittle alloys or sulphides 

 used in these exclude them from the list of available elements 

 when the elements are to be made very thin and are to have 

 several soldered joints. 



"We have numerous determinations of the electromotive force 

 of thermo-couples by Matthiessen and others, but it is impos- 

 sible to repeat their experiments, owing to the want of method 

 in the preparation of the couples, and the effects of impurities 

 in the metals used by them. 



The effect of physical state of the metal upon its thermo-elec- 

 tric height is clearly seen in Jenkins' table, compiled from 

 Matthiesen's experiments. Here the thermo-electric height of 

 antimony pressed wire is 280 C. G. S. units ; but for the same 

 metal with the equator of a crystal 2640. We are not assured 



