716 ANNUAL REPORT 
set. Narrow iron tampers are used to tamp the concrete into the mold. 
The top of the block is troweled smooth before removing it from the form. 
After three or four hours, or as soon as the concrete has sufficiently set, 
the blocks are wet down, water being applied twice a day for three or 
four days. The blocks are allowed to set ten days or more before being 
laid in the wall. 
Four men can lay about 60 blocks a day, equal to about 2,200 to 
2,500 bricks, or 112% square feet of wall surface. 
The concrete is made of 1 part Portland cement and 5 parts coarse 
sand. ‘Tests made upon such blocks at four months of age have shown 
80,000 pounds compressive strength. Figure 23 shows the Palmer ma- 
chine which is about two feet wide, three feet long and three and one-half 
feet high. Figure 24 shows the various shaped blocks and the purpose 
for which each is made. Figure 25 shows a residence under construction 
near Indianapolis, Ind. Figure 26 is from a picture of a residence in 
Springfield, Illinois. 
Fig. 24.—Palmer Concrete Hollow Blocks. 
Mr. Palmer claims that each standard block.takes the place of forty 
bricks; that each block can be made for twenty-two cents and hence 
economically replaces brick at $5.50 per one thousand. And further, that 
these blocks can be laid much more rapidly than brick, saving something 
also in labor. 
An Estimate of the Cost of Making the Palmer Block.—Assume 
cement to cost $2.00 per barrel, sand, $1.60 per cubic yard, common labor, 
$1.50 per day, with the foreman’s wages $2.25 per day, the estimate to be 
based upon the work of one machine using four men. The regular block 
contains 14 cubic feet of material and weighs about 165 to 170 pounds. 
Assuming the weight of cement at 80 pounds and that of sand at 100 
pounds and assuming that four men can make 100 blocks per day of eight 
