Trowbridge and Hutchins — Oxygen %n the Sun. 263 



and folded argillaceous slates. Farther south and west these 

 slates may be traced into continuity with mica-schists, which, 

 on the Mississippi River, in the vicinity of Little Falls, are 

 staurolitic and garnetiferous. These upper horizons of the 

 Animike are the counterparts of the upper horizons of the 

 iron-bearing series in the Penokee region and again in the 

 Marquette region of Michigan. 



The Animike rocks of this region are thus conformably 

 placed upon an older series of schists and granites, and lie 

 unconformably beneath the newer Keweenaw series, the latter 

 unconformity being indicated by the manner in which the 

 basal beds of the Keweenaw series traverse the courses of those 

 of the Animike', and by the folded condition of the Animike 

 slates in the vicinity of the St. Louis River ; the crumplings in 

 this case having plainly preceded the accumulation of the 

 Keweenawan beds. 



Thus the Animike series occupies very plainly the strati- 

 graphical position of the original Huronian, and of the various 

 iron-bearing groups of the south shore of Lake Superior. 

 Since it is also intrinsically so extraordinarily like the Penokee 

 series as to leave no doubt of their identity ; and since the 

 Penokee is as evidently the equivalent of the original Huro- 

 nian, we seem to be left no choice as to calling the Animike 

 Huronian also. 



[To be continued.] 



Art. XXIX. — Oxygen in the Sun; Contributions from the Phys- 

 ical Laboratory of Harvard University ; by John Trow- 

 bridge and C. C. Hutchins. 



[From the Proceedings of the American Academy of Arts and Sciences, vol. 

 xxiii; Investigations on Light and Heat, made and published wholly or in part 

 with Appropriation from the Rumford Fund. Presented March 9, 1887.] 



Since the time it was announced that hydrogen existed in 

 great abundance in the sun's atmosphere and was a controlling 

 element in its economy, there have been no more interesting 

 questions in solar physics than those touching the presence of 

 other gases in the sun's body and atmosphere; and when we 

 consider the important part that oxygen plays in terrestrial 

 affairs, the great variety of combinations into which it enters, 

 and its high constituent percentage in the composition of the 

 earth itself, a peculiar interest, second to that of no, other ele- 

 ment perhaps, attaches to its probable presence in the sun. 



The investigation of the spectrum of oxygen as a research 

 by itself, and as connected with its presence in the sun, has oc- 

 cupied many eminent physicists; but the fact that the latest 



