244 BULLETIN! MUSEUM OF COMPARATIVE ZOOLOGY. 
interstices of the rock. Thus it would appear that the residual prod- 
ucts of the disintegration would be quartz grains and clay, shading 
downward through successively less decomposed material, into the 
unchanged rock. In this case, however, it is probable that the loos- 
ened, undecomposed material below would be relatively coarse and 
not of sufficiently fine texture to form arkose of the type exposed at 
Pondville. Should such materials be subjected to rapid transportation 
and deposition, beds of sandstone, clay, and coarser granitic fragments 
would undoubtedly be formed, but it is not probable that the feldspars 
of gritty texture would have escaped some degree of chemical decom- 
position. 
For the production of true arkose it would seem that climatic con- 
ditions are needed that are not so favorable for the decay of the feld- 
spars as those suggested by Professor Shaler. The suggestion of 
Oldham that extreme severity of climate will account for the occur- 
rence of undecomposed feldspars in feldspathic sandstone appears to 
be borne out by the character of many glacial accumulations; for 
fragments of fresh feldspar are frequently found in boulder-clay and 
in fluvio-glacial deposits. Nevertheless, true arkose is not found in 
glacial deposits. The supposition of extreme dryness, suggested 
by Oldham as an alternative, might indeed account for the comminu- 
tion of granitic rocks without chemical decay and for the production 
of fragments of undecomposed feldspar; but in the deserts of warm 
temperate or tropical latitudes, where arid conditions are displayed 
to best advantage, no deposits resembling arkose have been observed. 
According to Shaler, there are no observations on record of arkose 
now in the process of formation (Shaler et al., p. 53). The prime 
requirement seems to be a set of climatic conditions that favor mechani- 
cal disintegration without permitting much chemical decay. It has 
been shown that none of the above mentioned conditions iş entirely 
favorable. Probably the true conditions are intermediate between 
the extremes noted. A moderately cool and arid climate, such as 
would obtain at moderately high altitudes in the lee of lofty mountain 
ranges, or in continental interiors, would more likely be suitable. 
Significance of Color. In all three basins red colors are found in 
some members of the Carboniferous series and in the sediments of 
the Norfolk and Narragansett Basins they are conspicuous features. 
"The red color furnishes an important clue to the geographical condi- 
tions of the time, when the now consolidated strata were still loosened 
waste, unremoved from its parent ledges. As Shaler remarks, the 
red color in sediments may be due to several causes: the waste from 
