16 Transactions Texas Academy of Science. [ 62 ] 
mill on the San Marcos river. The dam is ninety feet long and is built 
of timber frame work and rock, like that of J. W. Teller’s, a few miles 
above. A wing of timber sheeting two feet higher than the dam joins it 
to the bank opposite the mill. The dam in its normal condition gives a 
head of six feet on the turbines, but this can be increased to eight feet 
by a system of flash boards that are' raised above the dam when needed 
and taken off when they are not required. These flash boards consist 
merely of 2x4-inch pieces two feet long that are bolted to transverse tim- 
bers in the top of the dam (spaced about six feet), and which, can bo 
raised nr lowered at will. The 'under, sides of these 2x4 pieces are 
notched, and when raised are propped np by means of sticks in these 
notches that rest upon the apron of the dam at the toe. Planks 2x12 are 
then placed against these 2x4 props thus held upright, and raise the water 
up to the required eight feet. The power is derived from one 66-inch 
Morgan Smith turbine, which gives thirty-five horse power with a six 
foot head and fifty-five horse power with an eight foot head. This is 
utilized in operating a gin, corn mill, and small waterworks and electric 
light plant. The machinery consists of seven Munger gins, two Meyer’s 
pumps of about 200 gallons capacity, one 1 1 5-volt direct-current dynamo, 
a com mill, and a fifty horse power Atlas engine and boiler. The engine 
is required when the mill and gin are run to their full capacity, and is 
connected directly to the turbine shaft. The entire cost of the plant was 
about $10,000, and it was built in 1879. 
At the town of Prairie Lea is located the gin and corn mill of J. J. 
Jones. His dam is 120 feet long, eight feet high, and is constructed of 
timber frame work filled in with stones. It was built in 1896. The 
power is derived from one 61-inch iVlcot turbine, which produces forty- 
five horse power under the seven foot head obtained. This is utilized in 
operating a gin, corn mill, and one 110-volt Wiley dynamo. The total 
Cost of the plant was about $2400. 
Three and one-half miles north of Luling a dam of timber cribbing, 
filled with rocks, about 120 feet long, is constructed across the San Mar- 
cos river. The power obtained by it is used in operating a saw mill, gin, 
grist mill, and the Luling electric light plant. A head of about nine 
feet is obtained and one 50-inch Sampson turbine produces about sixty- 
seven horse power. The dam was first built about thirty years ago, but 
has been repaired from time to time, and has, therefore, been practically 
renewed at least once since then. The foundation is the muddy bed of 
the river. 
Farther down stream and nearer the town is the dam of F. Zedler, 
which furnishes power for the operation of a cotton gin, grist mill, and 
-the water supply machinery of the town. The dam is about sixty feet 
long and is constructed of timber cribbing backed with stone and gravel. 
It is built in the form of two cribs, placed one upon the other, resting on 
