86 
GEOLOGY AND MINERAL RESOURCES OF MISSISSIPPI. 
sand and clay, which forms a natural cement. When placed upon a street or railroad the 
rains and constant travel over it cause the material to cement into a rock-like mass. Some 
railroad men object to the gravel from the eastern section of the State because it often 
cements so tightly that it prevents the ties from drying out and makes the roadbed too rigid. 
This cementing quality makes it all the more desirable for common road material. 
When shipped for any great distance over the railroads gravel becomes an expensh e road 
material. In Coahoma County experiments have recently been made in building roads 
with gravel from Tishomingo County. The cost of grading and putting a layer of gravel 8 
inches thick in the center of the road was $5,000 per mile, or $50 per carload. 
The other section of the State where gravel is present is along the western half. This is 
more extensive than the eastern area, but the deposits are much thinner, the gravel in many 
places being but a few inches thick. The gravel of the western area does not possess the 
cementing qualities of the Tishomingo gravel. It is little more than a mass of round, water- 
worn pebbles which when used as a road material are easily pushed aside by wheels of vehi- 
cles and horses' feet. For this reason it has been called "crawling gravel." Where used as 
a railroad ballast it is greatly improved by being mixed with sand and clay. 
BURXED CLAY. 
In some of the later formations of the State there is a bluish-gray to dark-colored tough 
gumbo (lav which has been experimented on for making roads. This clay is found through- 
out the Yazoo delta region, except where it is covered by silts and sands along the streams. 
Some of the citizens of Clarksdale, Coahoma County, have thought forsome time that this 
tough gumbo clay could be burned and utilized for a road material. They accordingly inter- 
ested the National Government in the matter and a man was sent there during the fall of 
1903 to make an experiment with the clay for this purpose. The road was first graded, the 
center of the roadbed raised, and good ditches cut on either side. Two rows of logs 6 to 8 
inches in diameter were placed on either side of the roadbed, parallel to it, and these were 
cross laid with good, solid, dry wood, of sufficient amount when burned to completely 
dehydrate the clay. Enough clay was then thrown upon the wood to make about 8 to 10 
inches of clinker in the center of the roadbed. After the wood is all burned to an ash the 
overlying burned clay settles down on the roadbed and the road is then ready for travel. 
A specimen of the unburned clay used at Clarksdale was analyzed in the laboratory of the 
United States Geological Survey and was found to contain 8.69 per cent of chemically com- 
bined water. A specimen of the burned clay was also analyzed and it was found to be prac- 
tically dehydrated. The following are the analyses of the two clays: 
Analyses of clay used in road experiment at Clarksdale. 
Un- 
burned 
clay. 
till rued 
clay. 
Loss at 107° 
Loss by ignition. 
Per cent, 
5.32 
8.69 
Per cent. 
0.10 
.21 
The road was constructed at a cost of $2,000 per mile. This included grading, fuel, and 
labor. After giving the road a fair test Walter Clark, of Clarksdale, asserts that it has been 
satisfactory. It is easier on the horses' feet and vehicles and does not get dusty or muddy. 
A more thorough test is now being made on another road near Clarksdale. Should the 
experiment prove to be successful the question of road building throughout the delta 
will be solved and the condition of the country greatly improved. 
