STATE GEOLOGIST. 313 
it six times from one hand to the other, maintained 6 inches apart; the- 
ball is then pressed into the rubber ring, through the larger opening, 
smoothed off, and placed on a glass plate (on its large end) and the 
smaller end smoothed off with a trowel; the paste, confined in the ring, 
resting on the plate, is placed under the rod bearing the cylinder, which 
is brought in contact with the surface and quickly released. 
32. The paste is of normal consistency when the cylinder penetrates 
to a point in the mass 10 mm. (0.39 in.) below the top of the ring. 
Great care must be taken to fill the ring exactly to the top. 
23. The trial pastes are made with varying percentages of water 
until the correct consistency is obtained. 
34. The committee believes that the normal consistency should 
produce a rather wet paste, since this consistency tends to greater uni- 
formity in the mixing, and there is less liability of compressing the 
briquettes during the molding, 
35. Having determined in this manner the proper percentage of 
water required to produce a neat paste of normal consistency, the proper 
pereentage required for the sand mortars is obtained from an empirical 
formula. 
36. The committee hopes to devise such a formula. The subject 
proves to be a very difficult one, and, although the committee has given 
it much study, it is not yet prepared to make a definite recommendation. 
TIME OF SETTING. 
37. Significance.—The object of this test is to determine the time 
which elapses from the moment water is added until the paste ceases to be 
fluid and plastic (called the “initial set”), and also the time required for it 
to acquire a certain degree of hardness (called the “final” or “hard set’’). 
Uhe former of these is the more important, since, with the commencement 
of setting, the process of crystallization or hardening is said to begin. 
As a disturbance of this process may produce a loss of strength, it is 
desirable to complete the operation of mixing and molding or incorporating 
the mortar into the work before the cement begins to set. 
38. It is usual to measure arbitrarily the beginning and end of the 
setting by the penetration of weighted wires of given diameters. 
39. Method.—For this purpose the Vicat needle, which has already 
been described in paragraph 30, should be used. 
40. In making the test, a paste of normal consistency is molded and 
placed under the rod (L) (figure 79), as described in paragraph 31; 
this rod, bearing the cap (D) at one end and the needle (H), 1 mm. 
(0.039 in.) in diameter at the other, weighing 300 er. (10.58 oz.). The 
needle is then carefully brought in contact with the surface of the paste 
and quickly released. 
