Erratum

ADDITIONS AND CORRECTIONS. Page 99, line 5, for Protagoras, read Protogenes 186, last line, for southerly, read northerly 204, line 4, for heat, read iodine 272, line 17, for about 10°, read between 12° and 14° 275, line 18, for 39°, read 37° 30' 277, line 17, for nearly $\frac{1}{2}$, read less than $\frac{1}{3}$ Id. lines 21 and 23, for 141°, read 141° 53' 278, line 12, at the word crystallized, insert the following as a note: The interrupting stratum is crystallized in a different manner from the rest of the rhomboid. The position of its axes with respect to those of the rhomboid, and the singular optical phenomena which arise from this cause, will be described in another paper. 288, Note, line 4, for parallel, read perpendicular