166 Gooch and Kreider — Chlorine for Laboratory purposes. 



It may be allowed to suspect, then, that the cleavage of the 

 Thomson series was developed at the same time and by the 

 same forces as that of the Mesabi Range and as the correspond- 

 ing structures which are found further north, in Minnesota 

 and Canada. If this be the case, the Thomson series must 

 be put below the unconformity exhibited upon the Mesabi, 

 and provisionally correlated with the Keewatin. The sec- 

 ondary cleavage shown in the Thomson slates, as at Cloquet, 

 may for the present be supposed to be more local, and to have 

 had its cause near by, — perhaps connected with the advent of 

 some of the larger masses of igneous Keweenawan rock, as we 

 have noted that the rare third cleavage accompanied the intro- 

 duction of the narrow dikes. 



We must also take into account the considerable folding which 

 the Thomson series has undergone, as distinguished from the 

 undisturbed condition of the Animikie. In this respect also 

 it resembles more the Keewatin. The occurrence in the 

 Thomson slates of many veins of quartz and the generally 

 indurated appearance of the rocks accords with the appearance 

 of Mesabi Keewatin, and suggests that the beds have been 

 deeply buried. 



The Animikie-Keweenawan Unconformity. 



If it shall be finally considered that this suggested correla- 

 tion is correct, we shall appear to have in this region Keewatin 

 strata directly overlaid by the Keweenawan rocks which are 

 exposed in great quantities a little further east. If we believe 

 in the original extension of the Animikie sediments over the 

 whole Lake Superior basin, it will follow from this correlation 

 that the erosion interval between the Animikie and the Ke- 

 weenawan was very great. 



Minneapolis, May 3, 1894. 



Aet. XXIII. — The Generation of Chlorine for Laboratory 

 Purposes; by F. A. Gooch and D. Albert Kreider. 



[Contributions from the Kent Chemical Laboratory of Tale College— XXXI1L] 



That chlorine may be generated in a state of greater or less 

 purity, variable with the conditions of evolution, by the action 

 of hydrochloric acid upon potassium chlorate has been shown 

 by Pebal* and Schacherl,+ but the application of this fact to 

 the practical generation of chlorine for the purposes of the 



* Awn. der Chern., clxsvii. 1. f Ibid . clxxxii, 197. 



