218 ANNUAL REPORT 
must be subject to the direction of the Engineer Commissioner, as due con- 
sideration must be had as to the style, design and adaptability of the machine 
used to produce & mixture acceptable to him. 
lf the materials are mixed by hand labor, the operation must be performed 
on platforms of water-tight construction by competent labor, in accordance 
with the following instructions: 
The dimensions of the platforms must be such as to provide an area 
sufficient to allow the entire mixing operations to be done upon them in a 
thorough and complete manner, in accordance with these specifications, and 
will depend upon the yolume of the material used in the batch; in batches 
requiring a full barrel of cement, the dimensions of the platform will not 
be less than ten (10) by twelve (12) feet, or its equivalent area, of suitable 
form, and no larger batches than these shall be made by hand labor. 
The required quantity of sand will be spread upon the board or platform, 
dry, and covered with the cement, in its proper proportion, when the material 
shall be thoroughly mixed and incorporated, by turning it with shovels not less 
than six (6) times. When sufficiently mixed, the mass will be so spread 
and shaped as to form a basin for the water which is to be added to make 
the mortar. The required quantity of water will now be poured into the basin 
thus formed and incorporated with the dry substance, by the use of hoes and 
shovels, so as to prevent any loss of material. The mortar will then be 
spread over the surface of the platform in an even and regular layer, pre- 
paratory to the reception of the stone and gravel, which, having been pre- 
viously drenched, will immediately be deposited and evenly spread over the 
mortar. } 
When. the entire quantity of the aggregate has been deposited and spreaa 
on the platform, as above, the mass shall be thoroughly mixed by turning 
it over with shovels, not less than four (4) times, until every particle of the 
metal has been completely enveloped in mortar; and until every particle is 
so enveloped, to the satisfaction of the Engineer Commissioner or his agent 
the mixing process must be continued. The order of turning must be so 
regulated that the last turn made will place the material in a single pile at 
or near the center of the board, preparatory to its removal to the place for it 
in the work. 
In removing the concrete from the platform care must be taken to pre- 
serve the incorporation, which can best be done by shoveling it from the base 
at the edges of the pile, toward the center of it, and at the same time cutting 
down the apex of the pile with a hoe or shovel, in such manner as to avoid 
an accumulation of loose stones. 
Stone and gravel used in the concrete must not be drenched in the vehicles 
used to deliver it upon the platform, unless proper arrangements are made 
to drain the receptacles, but shall be wetted before they are placed therein. 
Concrete shall not be used after it has shown evidence of beginning to set, 
and no concrete that has once set shall be used as aggregate for a new batch. 
The work of mixing and spreading shall be done as expeditiously as possible. 
Any material condemned as unfit for use, or not conforming to the spec- 
ifications, must be immediately removed from the site of the work. The con- 
tractor must provide suitable facilities to determine the quantities and quality 
of the materials used in the concrete, so that they may be readily ascertained 
at all times. | 
J2, Laying.—Grade stakes of suitable character must be set to determine 
anu regulate the grade for the material as it is deposited in the work, and 
straight edges or other equally efficient devices used to insure a regular and 
