564 



THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



water was exceptionally low. He farther stated chat the sandstone at 

 the junction was continuous with that seen below; that, it extended 

 across the stream and into the banks on both sides; ^while the baking 

 and induration of ,it showed that it must have been overflowed by some 

 heated rock. Again : the basaltic rock extended across the stream into 

 both banks, and was found to underlie the conglomerate, and that ho 

 dug the debris of the foi'mcr out of the overlying base of the latter. All 

 this, he said, showed conclusively that these rocks were in situ, and 

 proved that hero the eastern sandstone and Keweenawan series were 

 one and the same ; also that this series could not be maintained, as first 



established." * 



Irving further denies the general correctness of Wadsworth's pre- 

 viously published statement relating to the sandstone quarry near 

 Torch Lake {ante, pp. 117, 118), and maintains that, while he (Irving) 

 finds traces of the trappcan material in the sandstone, he docs not find 

 any of the porphyry material belonging to the conglomerates of the 

 *' Keweenawan series." This claim proves too much, for if this sand- 

 stone had been deposited against the mixed lava flows and detrital 

 rocks of the copper^bearing series as Irving holds, and made up of their 

 ruins, there the sandstone should be full of their debris, and the old 

 rhyolitic and trachytic material ought to bo far longer retained than the 

 more easily perishable basaltic material; since even in the sandstones 

 intercalated with the traps the basaltic debris is comparatively rare. 

 Now Irving's statements are directly opposed to his own views ; and the 

 same may be said of the testimony of all those who claim that the sand- 

 stone near the traps is composed of different materials from those of the 

 detrital rocks of the so-called Keweenawan series. 



Wadsworth has since re-examined the specimens in the collection 

 made with express reference to retaining the evidence in behalf of his 

 previous statements, {ante, pp. 117, 118,) and he reiterates those state- 

 ments with the exception of this correction, that on page 117, third 

 line from the bottom, the word felsiiic is misprinted fehhjxdhic, as the 

 context shows. He finds in these specimens an abundance of the bi- 

 pyramidal quartz peculiar to ancient and modern rhyolitic rocks, and 

 also the variation between the bedding planes and jointing, both being 

 evident in the hand specimens. The previous statement {ante, p. 488), 

 that Irving had adopted Wadsworth's view that the pebbles of the Ke- 

 weenaw conglomerates were largely old rhyolites and trachytes, Irving 

 denies, since the director of the U. S- Geological Survey had misstated 



* Science, 1884, III. 553. 



