CHEMICAL COMPOSITION. 
Selected analyses of roofing slates — Continued. 
35 
I. 
II. 
III. 
IV. 
V. 
VI. 
VII. 
VIII. 
IX. 
X. 
XI. 
XII. 
XIII. 
XIV. 
MnO (manganous 
■ 0.10 
1.00 
0.31 
3.41 
0. 586 
- 0.16 
2.88 
0. 20 
.11 
o3.70 
0.06 
.05 
.12 
«2.74 
2.64 
0. 16 
. 09 
.10 
a2.21 
3. 97 
0.05 
.54 
.03 
3.94 
0. 30 
.06 
. ()'.) 
a3.62 
P2O5 (phosphoric 
S0 3 (sulphuric ox- 
ide) 
. .022 
3.385 
. 051 
4.35 
H 2 
FeSo 
4.61 
3.25 
3.17 
3.52 
CoO (cobaltous ox- 
ide) 
Trace 
Total 
99.76 
2.81 
99.96 
99.76 
99.38 
100.20 
99.98 
99.801 
100. 10 
100. 04 
100. 17 
100. 10 
99.88 
100. 09 
99.80 
Specific gravity b. . . 
2.89 
2.78 
2.83 
a Combined water. 
bThe specific gravity of the Festiniog black slates of Wales was determined as 2.751 at the physical 
laboratory of Williams College in 1899. Since the publication of Doctor Hillebrand's note on New 
York and Vermont slates, Reade and Holland find as a mean of 13 Welsh slates Ci\>0 3 , 0.003; Vo0 5 , 
0.032; ZrOo, 0.022. See Proc. Liv. Geol. Soc. (1900-1901), p. 101, and table. 
cSpec. grav. from Merriman. 
I. Gray roofing slate, best quality, Delabole, Camelford, Cornwall; two analyses by J. A. Phillips, 
London, Edinb. and Dublin Phil. Mag., 4th ser., No. 27, pp. 95-96, Feb., 1871. 
II. Purple roofing slate, Fumay, Ardennes, northwest France; by A. Renard, Recherches sur la 
composition et la structure des phyllades ardennais; Bull. Mus. Roy. d'Hist. Nat. de Belgiqne.Vol. I, 
p. 239, 1882. 
III. Green roofing slate beds from purple, Fumay, Ardennes, as above. 
IV. Blue-gray roofing slate, La Richolle quarry, Rimogne, Ardennes, northwest France; by Elem- 
ent, pub. by A. Renard, op. cit. supra, p. 233. 
V. Roofing slate (probably black, Devonian), Westphalia; by H. von Dechen; Roth. Allgem. und 
Chem. Geol., II, pp. 586, 587, 1884. (107.) 
VI. Roofing slate (color not given, Devonian), Frankenberg, near Goslar, in Prussia; by A. von 
Groddeck; Jahrb. pr. Geol. Landesanst, 1885-86; quoted in Roth. Allgemeine Chem. Geol., II, pp. 
586, 587. 
VII. Black roofing slates ("Peach Bottom") from J. Humphreys Co.'s quarry, half a mile east of 
Delta, York County, Pennsvlvania; by Andrew S. McCreath, in 2d Geol. Surv. Pa., Reporl of Prog- 
ress, 1877, Vol. CCC, pp. 269, 270, 1880. 
VIII. Bluish roofing slate of Carboniferous age, Mohradorf, near Wigstadl, Austrian Silesia; by 
Nikolic, in Tschermaks Min. Mitth., 1871, p. 207; quoted by Roth, op. cit. supra, pp. 588-589. 
IX. Blue slate, Glyn quarries, Llanberis, Wales; analysis made at Museum of Practical Geology, 
London, for George Maw, Geol. Mag., London, 1868, vol. 5, p. 123. 
X. Reddish roofing slate (best), Alexandra quarrv, Moel Tryfaen, North Wales. Anal, by Reade 
and Holland, Proc. Liverpool Geol. Soc. (1899-1900), 1900. (Anal. No. 1.) 
XL Very dark banded roofing slate, Llansantfraid, Glyn Ceiriog, near Llangollen, North Wales. 
Anal, by Reade and Holland, Proc. Liverpool Geol. Soc. (1899-1900), 1900. (Anal. No. 2.) 
XII. Verv dark roofing slate, Moel Ferna, North Wales. Anal, by Reade and Holland, Proc. 
Liverpool Geol. Soc. (1899-1900), 1900. (Anal. No. 3.) 
XIII. Green roofing slate from quarrv between Camlvn and Cemmaes, Anglesey. Anal, by Read ) 
and Holland, Proc. Liverpool Geol. Soc. (1899-1900), 1900. (Anal. No. 4.) 
XIV. Green roofing slate, Velenhelli, Wales. Anal, by Reade and Holland, Proc. Liverpool Geol. 
Soc. (1900-1901), p. 112. (Anal. No. 6.) 
The fifteen complete analyses of New York, Vermont, and Pennsylvania roofing 
slates made by the chemists of the United States Geological Survey and given under 
the descriptions of those slates are summarized in the following table. Wherever 
several analyses were made of one kind of slate the average is given. The rarer 
elements and water below 110° C. have here been thrown together. 
