Hidden and Mackintosh — Polycrase of the Oarolinas. 423 



(4) For work with a bolometer or similar instrument, under 

 the same conditions that apply in the case of the thermopile. 



(5) For the measurement of a constant or variable current, 

 where it is desirable for any reason to take readings quickly. 

 For example, the initial value of the current from a cell which 

 is subject to rapid polarization may be determined by the first 

 throw of the needle. 



Other applications of the method will doubtless suggest 

 themselves. It is with the hope that a phenomenon which at 

 first appears to be merely a matter of curiosity, may thus be 

 made of practical value in the laboratory, that this note is 

 presented. 



Art. LII. — Supplementary Notice on the Polycrase of North 

 and South Carolina; by W. E. Hidden and J. B. 

 Mackintosh. 



The occurrence and composition of this mineral were 

 partially announced by us in volume xxxix, pp. 302-306, 

 of this Journal (June, 1890), and the localities have received 

 no development of moment since that publication. 



The South Carolina locality is distant about four miles from 

 Marietta, in Greenville County, and is situated otherwise as 

 before described. As to the form of the mineral, we have 

 some interesting features to add to our previous statements 

 and we here subjoin two figures (1 and 2) representing the 



two types observed and a corrected list of occurring planes 

 with the angles obtained by using a contact goniometer. The 

 planes observed are as follows, those marked with an asterisk 

 (*) are new : 



a (010, i-i) d (103. £-£)* V ( 133 » !-J) 



~b (100, i-i) u (011, 14) z (233. 1-|)* 



c (001,O)* 5(021,2-!) 3(130,2-3) 



1m. Jour. Sci — Third Series. Vol. XLT, No. 245. — May, 1391. 

 28 



