122 SLATE DEPOSITS AND^INDUSTRY OF UNITED STATES. 
outcrops, indicates its probable discoloration on prolonged exposure, so that it belongs 
in the "fading" group of clay-slates. But these characteristics do not affect its 
serviceableness for indoor purposes. 
The principal features of these West Virginia slates are stated in tabular form 
opposite page 124. 
MERRIMAN'S RECENT TESTS OF CERTAIN MAINE, NEW YORK, 
PENNSYLVANIA, VERMONT, AND VIRGINIA SLATES. 
In view of the incompleteness of published data as to the physical properties of 
American rooting slates, Doctor Day, chief of the division of mineral statistics of the 
United States Geological Survey, induced Prof. Mansfield Merriman, of Lehigh Uni- 
versity, to apply his well-known methods of testing roofing slates to typical speci- 
mens from nine important localities. The specimens were obtained from various 
firms and forwarded to him. Professor Merriman's communication to Doctor Day, 
containing his full report on the results of these tests, follows: 
The following is .-i report of the results of the tests of thirty-three specimens of roofingslate received 
at our laboratory from May 6 to May 13, 1905. The tests have been made according to the methods 
described in my paper on "The strength and weathering qualities of roofing slates," in Transactions 
of American Society of Civil Engineers, September, 1892. 
All the specimens were 12 by 24 inches in size. The following is a statement of the marks placed 
upon them and of their mean thicknesses: 
CI, C2, <'::. ci designate lour blue slates from the Chapman Slate Company, Chapman Quarries, Pa., 
the mean thicknesses being 0.228, 0.204, 0.216, 0.222 inches, respectively. 
Wl, W2, W3, W4 designate four blue slates from the Williams Slate Company, Arvonia, Va., the 
mean thicknesses being 0.202, 0.195, 0.206, 0.263 inches, respectively. 
PI, P2, I'::, l'l designate lour blue slates from A. L. Pitts, Arvonia, Va., the mean thicknesses being 
0.232, i). 200, 0.204, 0.194 inches, respectively. 
Bl, B2, B3 designate three blue whites from the Merrill Brownville Slab' Company, Brownville, Me., 
the mean thicknesses being 0.220, 0.195, 0.210 inches, respectively. A fourth piece sent by this firm 
was accidently broken. 
Mol, Mo2, Mo::. Mo| designate four blue slates from Monson Consolidated Slate Company, Monson, 
Me., their mean thicknesses being 0.238, 0.227, n.'_'::7, 0.225 inches, respectively. 
VI, V2designate two green slates from Vermont Unfading Green Slate Company, Fair Haven, Yt., 
their mean thicknesses being 0.222, 0.262 inches, respectively. Two otherpiec.es sent by this firm were 
found broken in the package. 
Rl, R2, R3, Kl designate four green slates from Rising & Nelson Slate Company, West Pawlet, Vt., 
their mean thicknesses being 0.260, 0.167, 0.224, 0.213 inches, respectively. 
M5, M6, M7. M^ designate four green slates from Mathews Consolidated Slate Company, Boston, 
Mass., their mean thicknesses being 0.194, 0.222, 0.187, 0.205 inches, respectively. The labels on these 
slates were marked "Quarry N. E." 
Ml, M2, M3, M4 designate four red slates from Mathews Consolidated Slate Company, Boston, Mass., 
their mean thicknesses being 0.190, 0.180, 0.174, 0.186 inches, respectively. The labels on these slates 
were marked "Quarry E." 
The following table gives the results of the tests of the above 33 specimens for strength, toughness, 
density, softness, porosity, and corrodibility, and also the means for each of the nine different kinds 
of slate. 
Color and firm. 
Mark on 
speci- 
men. 
Strength- 
modulus ot 
rupture in 
pounds per 
square 
inch. 
Tough- 
ness—ul- 
timate 
deflec- 
tion in 
inches on 
supports 
22 inches 
apart. 
Density- 
specific 
gravity. 
Softness- 
amount in 
grams 
abraded 
by 50 turns 
of a small 
grind- 
stone. 
Porosity- 
percent of 
water ab- 
sorbed in 
24 hours. 
Corro- 
dibility— 
per cent 
of weight 
lOSl in 
acid solu- 
tion in 63 
hours. 
Blue; a Chapman Slate Co . 
CI 
C2 
C3 
C4 
Means . . 
8,410 
12, 490 
7, 420 
9,540 
0.21 
.24 
.16 
.24 
2.775 
2.780 
2. 734 
2.766 
0.171 
.218 
.234 
.213 
0.221 
.290 
.150 
.263 
0.336 
.301 
.560 
. 334 
9,460 
.212 
2.764 
.208 
.231 
.383 
a Designated as very dark gray in table facing page 124 
