Expressing the above statement as a formula we shall have Art 3 Portland Cement Continued 3 or, must not exceed one.

The mean value of this ratio for twenty representative American brands is found to be .915. Values of .76 and .99 respectively were given by two well-known German brands.

The above discussion is based upon the theory evolved by several authorities from the results of experiment. Much doubt has been thrown upon this theory, however, by the recent investigations of Messrs. Day and Shepard in the Geo-physical Laboratory of the Carnegie Institution. In the Journal of the American Chemical Society for September, 1906, Messrs. Day and Shepard presented their results, showing that the only definite compounds of lime and silica are the metasilicate CaOSi02 and the orthosili-cate Ca2Si04. This discovery will necessitate the modification of present accepted theories, but as yet the investigations have not been carried far enough to lead to definite conclusions.

10. The analyses of thirty-two brands of Portland cement, most of them of American manufacture, given in Table 2, are selected from various sources and illustrate the proportions obtaining in commercial products.

Table 2. Analyses Of Portland Cement

No.

Raw Materials.

Process.

Brand.

Location.

1

Limestone and Shale . . .

S

Alpena

Alpena, Mich.

2

Cement Rock and Limestone

D

Alpha

Alpha, N. J.

3

Chalk and Clay......

W

Alsens

Itzehoe, Germany.

4

Cement Rock and Limestone

D

Atlas

Northampton and Cop-lay, Pa.

5

Marl and Clay......

W

Brunson

Bronson, Mich.

6

Marl and Clay......

S

Buckeye

Harper, Ohio. Manheim, W. Va.

7

Cement Rock......

D

Buckhorn

8

Limestone and Clay ....

D

Catskill

Smiths Landing, N. Y.

9

Limestone and Clay .... Limestone and Clay . . . Limestone and Marl . .

D

Diamond

Middle Branch, Ohio.

10

D W

Dyckerhoff

Amoeneburg, Ger.

11

Cement Rock and Limestone

D

Edison

New Village, N. J.

12

Marl and Clay......

S

Empire

Warners, N. Y.

13

Marl and Clay.....

w

Germania

Lehrte, Germany

14

Cement Rock and Limestone

D

Giant

Egypt, Pa.

15

Limestone and Clay ....

D

Hudson

Hudson, N. Y.

16

Limestone and Clay ....

D

Iron Clad

Glens Falls, N. Y.

17

Chalk and Clay......

W

K. B. & S.

England.

18

Cement Rock and Limestone

D

Lehigh

Allentown, Pa.

19

Marl and Clay......

W

Medusa

Bay Bridge, Ohio.

20

Marl and Clay......

W

Medusa

Syracuse, Ind.

21

Cement Rock and Limestone

D

Nazareth

Nazareth, Pa.

22

Cement Rock and Limestone

D

Northampton

Stockertown, Pa.

23

Limestone and Clay ....

D

Old Dominion

Craigsville, Va.

24

Marl and Clay......

W

Omega

Jonesville, Mich.

25

Marl and Clay......

W

Peerless

Union City, Mich.

26

Cement Rock......

D

Red Diamond

Demopolis, Ala.

27

Cement Rock and Limestone

D

Saylors

Coplay, Pa.

28

Slag and Limestone . .

D

Universal

Chicago, 111.

29

Cement Rock and Limestone

D

Vulcanite

Vulcanite, N. J.

30

Marl and Clay......

W

Wolverine

Coldwater, Mich.

31

Clay and Waste Limestone

W

Wyandotte

Wyandotte, Mich.

32

Chalk and Clay......

W

Yankton

Yankton, S. Dak.

Note.Wet process is indicated by W; dry, by D; and semi-wet, by S.