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STATE GEOLOGIST. 133 
In protecting steel columns or girders, the wire lathing is furred 
out 2 inches or more from the member by specially designed metal clamps 
and bars, the space inside is then filled with cinder concrete before the out- 
side is plastered. 
The concrete used is I part Portland cement, 214 of sand and 6 parts 
cinder. It is never rammed solidly, but allowed to set in porous form. 
It dries out quickly, is light, and the porosity prevents the fracturing of 
the concrete under sudden changes in temperature. Concrete under these 
conditions weighs about 80 pounds per cubic foot. 
Strength of Roebling Arch.—To test the strength of the Roebling 
arch system, the New York Building Department in 1896 made a severe 
test upon a 4 foot arch. It was first subjected to a five hour fire test at 
temperatures ranging from 2,000° to 2,350 F. and then cooled by a | 
stream of water from a fire engine. A section of the arch 4 feet long was 
then cut free from the remainder of the arch and the middle 2% feet 
of this section was loaded with a load of 41,000 pounds, or a load of 2,556 
pounds per square foot over the entire arch, which safely withstood the 
test. The heat of the fire test was sufficient to fuse the brick side walls 
and to cause the surface of the brick to run down the wall like molten 
metal. Figures 68 and 60 illustrate other methods of using the system. 
Expanded Metal System.—lxpanded metal consists in sheet steel 
slit in regular lines and then the strips forced apart forming diamond 
shaped meshes. Sheets of this meta! are then laid over the girders with 
ends lapping and the concrete lightly tamped in around the metal. The 
metal is sometimes sprung in between beams as is done in the Roebling 
system. Expanded metal makes a very strong floor as is shown by a test 
made upon a floor slab for the Larkin Soap Co. of Buffalo, N. Y. 
A 4 foot 10 inch span of floor 3 inches thick and 13 feet 10 inches long was 
subjected to a uniformly distributed load of 2,333 pounds per square foot 
without indicating weakness. The load was then changed to a concen- 
trated load 12 inches wide in the center of the panel extending for full 
panel length. The floor panel broke when the total load amounted to 
4,855 pounds per square foot. Expanded metal is particularly adapted 
to thin partitions where the metal can be tacked to each side of metal or 
wooden studding and cement mortar plastered upon both sides forming 
a very durable solid wall of minimum thickness. 
Melan System.—The Melan system consists of concrete reinforced 
with steel I-beams, bent to conform to the tension surface of the 
structure. In this country it has been principally used in bridges. The 
I-beams vary in size to suit the requirements of the span and load. 
They are set at intervals of two or three feet apart laterally, and the lower 
flange is kept about three or four inches from the bottom face of the 
arch. As the concrete varies in depth from the crown to the haunch of 
