338
EXPOSITION AT VIENNA.
clay, one-eighth cement, one-eighth kaolin, and one-eighth fire-sand. The " cement” is a burned fire-clay.
In the best New Jersey clays no grit can be perceived when tested between the teeth. Analyses of good specimens show the following ingredients 1 :—
i.*
»•t
34
44
Silica,.
43.20
45.30
46.32
46.29
Alumina,.
39.71
37.10
39.74
40.09
Zirconia,.
1.40
1.40
-
-
Potash, .
.37
1.30
-
-
Lime,.
-
.17
.36
.50
Magnesia,.
-
.22
.44
-
Peroxide of iron, ....
.74
1.30
-
-
Protoxide,.
-
-
.27
.27
Water,.
14.25
13.40
12.67
12.67
* White clay from Burt’s Creek near South Amhoy.
f White clay from Trenton. J Cornwall, England.
Prof. Cook, state geologist of New Jersey, says of the potter’s clay, that it is tenacious, of a light-blue color ; a little gritty when tried between the teeth. When highly heated it becomes partially vitrified without losing its shape, and is thus well adapted for earthenware. And it can be heated sufficiently for salt-glazing without injury. The following analyses show composition at several localities :—
l.*
24
34
4.§
Silica,.
71.80
68.00
65.62
75.55
Alumina,.
19.05
23.66
20.88
19.04
Potash, .
.61
1.19
1.95
.10
Lime,.
.31
-
-
-
Magnesia,.
.79
-
.30
-
Oxide of iron,.
1.31
1.17
1.23
.71
Water,.
6.08
6.40
8.10
4.85
99.95
100.42
98.08
100.25
* Morgan clay, pits near South Amhoy. f Bank of Rancocas Creek, near Bridgebora.
\ Billingsport, on the hank of the Delaware, below the mouth of Mantua Creek. § Raccoon Creek, a mile above Bridgeport.
1 These and the following analyses for comparison are taken from the Geology of New Jersey, 1868, p. 683. Analyses 3 and 4 from Percy’s Metallurgy.