ITS MICROSCOPIC CHARACTERS 173 



called scHUerfels, and are usually looked upon as being of eruptive origin. 

 It can be readily seen that the present writer regards the series as forming 

 a progressive set of changes, coming down in regular order from the first to 

 the fifth ; but Dr. Carpenter took a different view. He found the remains 

 of eozoon in every one, but the fossil was best preserved in tlie last section 

 (fig. 5), and it was more and more illy defined in regular order, through 

 metamorphic action, following the retrograde arrangement, going from 

 figure 5 back to figure 1. 



The same ground was also taken by Dr. Carpenter in reference to the 

 sections shown in figures 5, 4, and 3, of Plate VII., although field evidence 

 has shown this rock to be of eruptive origin.* , Eozovn in various stages 

 of preservation was found by him in other sections, even including some 

 made from dolomitic veinstones. Sections of the felsite pebbles forming the 

 Calumet and Hecla conglomerate, and other bands of conglomerate on 

 Keweenaw Point, were shown Dr. Carpenter. The present writer in 1880 t 

 called attention to the simulative appearance of organic structure assumed 

 by their groundmass during the alteration of the rocks. On examining these 

 sections. Dr. Carpenter thought that the rocks must be of organic origin, and 

 these forms the remains of sponges and other protozoa. Now it is to be 

 remembered that the original source of these pebbles has been found by 

 Foster and Whitney, | and later by Irving, § in eruptive felsites bi-eaking 

 through the copper-bearing rocks. 



In the examinations made by Dr. Carpenter of the various sections laid 

 before him, it was noticed that the more the rock was altered, or the nearer 

 it approached a veinstone in character — or better, when it was a veinstone 

 — the more perfect and the better preserved were the fossils. 



Dr. Carpenter was frankly told the writer's views about the eosooii, the 

 origin of the rocks in question so for as known, the supposed mode of 

 production of these forms, and the object of their presentation to him; 

 and he as frankly and unreservedly gave his opinions. Of course, since Dr. 

 Carpenter's views have not been published over his own name, and were not 

 the fruits of long-continued critical study on the specimens in question, 

 they are not proper subjects for criticism — as his published views would be. 

 The object for presenting them here, is simply to call attention to the fact 



* Ante, pn 130-139 ; also Bull. Mus. Comp. Zool., 1880, VIL 60-06. 



t Bull Mus. Comp, Znol., 1S80, VII. 113-120. 



X Geology of Lake Superior, Copper Lands, 1S50, pp. 70, 71. 



§ Sec. Aim. Rep. Director U. S. Gaol Survey, 1881, p. 33. 



