ROOFING SLATES OF NEW YORK AND VERMONT. 
41 
Neither the condition nor the source of the nitrogen thus revealed can be stated 
with any degree of positiveness. It is found in the interior of fresh and unbroken 
nasses, and hence is not to be regarded as derived from infiltration of nitrogenous 
natter since the opening of the quarries. Whatever may be its manner of combina- 
tion, nitrogen is coming to be recognized as a primary constituent of many rocks and 
minerals. It seems probable that in the present instance its presence is to be attrib- 
ited to that of the organic matter which was doubtless not wanting when the mate- 
rials now composing the slates were originally laid down. 
Chromium and vanadium are probably minor constituents of all the slates. They 
ivere not looked for in making the foregoing analyses, but in connection with some 
nore recent work relating to the distribution of vanadium in the rocks of the earth's 
crust, « the sea-green slate 230a (A) and the red slates 201e (K) and '397 e (L) were 
examined. In 201 e there was found 0.017 per cent of vanadium as V 2 5 and 0.007 per 
cent of chromium as Cr 2 3 . In a mixture of equal parts of the two red slates there 
tvas found of V 2 5 0.008 per cent and Cr 2 3 about as in the first case. 
To the novice a cursory examination of the tabulated analyses might seem to indi- 
cate a greater diversity in essential composition than comports with the facts. Thus, 
:here seems to be, perhaps, little relation in composition, except qualitatively, between 
;he red slates 358d (J) and 397 e (L). Yet, after deduction of all CaO as phosphate 
ind carbonate, of all MnO as carbonate, and of enough MgO as carbonate to satisfy 
;he remainder of the C0 2 , also of the trace of pyrite, amounting to 16.58 per cent in 
ill, and calculating the remaining 83.80 per cent to 100, there result the figures 
*iven in the first column below, for comparison with which analyses 358d (J) and 
201? (K) of slates naturally altogether or nearly free from carbonates are partially 
reproduced : 
397e(L). 
358d (J) . 
201e(K). 
397e(L). 
358d(J). 
201e(K). 
5iO- . 
67.40 
.57 
13.84 
4.15 
1.70 
.07 
3.34 
67.61 
.56 
13.20 
5.36 
1.20 
.04 
3.20 
67. 65 
.58 
12.59 
5.61 
1.24 
.31 
3.27 
K 2 .. 
4.50 
. 62 
.44 
3.37 
4.45 
.67 
.45 
2.97 
4.13 
riOo 
NaoO 
.61 
y 2 o 3 
H 2 below 110° C 
H 2 above 110° C 
Total 
.40 
FeoO-i 
3.03 
?eO 
100. 00 
99. 71 
3aO 
99.32 
VtgO 
When it is borne in mind that a portion of the FeO in 397c should doubtless be 
credited to the carbonate, whereby an equivalent of MgO would be released for the 
silicate, it will be seen that the agreement as to FeO in the above comparison would 
be much closer, and the three slates may be said to have almost identically the same 
composition when compared in this manner. 
Applying a similar correction to the three analyses of 397a R, Q, and M, in the 
Drder named, we obtain the following corrected figures for the green spot, the purple 
rim, and the outer red, which bring into special prominence their relatively high 
silica contents as compared with all the other slates analyzed: 
3i0 2 . . 
rio 2 . . 
p 2 o 3 . 
Fe. 2 3 
FeO . . 
3aO.. 
MgO. 
397a (R). 
76.04 
.60 
10.90 
1.27 
1.23 
.06 
2.75 
397a (Q). 
73.64 
.58 
11.66 
2.04 
1.36 
.05 
3.25 
397a (M). 
71.59 
.53 
10.95 
4.33 
1.61 
.05 
3.77 
KoO 
4.15 
NaoO 
.26 
HoO below 110° C . . 
H 2 above 110° C . . 
. 29 
2.45 
Total 
100. 00 
397a (R). 
397a (Q). 
4.22 
.26 
.32 
2.61 
99. 99 
397a (M i. 
3.87 
.22 
.30 
2. 78 
a Distribution and quantitative occurrence of vanadium and molybdenum of rocks in the United 
States, by W. F. Hillebrand: Am. Jour. Sci., 4th ser., vol. 6, 1898, p. 209. 
