The inside walls are hung on double hinges so that the slightest upward motion of the moulds releases the post.

The "Bailey" Post Machine is made of cast metal. The sides taper and are hinged at the top. A hinged bottom plate holds the sides together. To release the post, the hinged bottom plate is removed and the sides spread.

The "Scott" Concrete Fence Post Machine is made of steel and makes a post with a U-shaped cross-section. This machine differs from the other in that it must be turned over to release the post.

The "Luck" Cement Post Mould is made in two sections of heavy galvanized iron, held together by clamps on the flange. The

posts are octagonal in shape and are cast in a vertical position, using wet concrete. It is practically the only post mould in which the post is cast in a vertical position.

Methods of Reinforcement.-Various methods of reinforcing fence posts are in use and recommended by the various manufacturers. The advantages of some of these systems of reinforcement are more fanciful than real, and in some cases the reinforcement recommended would materially increase the cost of the post. For ordinary conditions, plain rods, wire, etc., may be used and entirely satisfactory results obtained. Scrap steel may frequently be used to advantage. The matter of reinforcement should depend entirely on what is most easily and economically available. For posts

where a dry concrete is used, however, some sort of mechanical bond between the reinforcing and the concrete would be advisable.

TABLE XIV.-QUANTITY OF MATERIAL FOR FENCE POSTS.* All posts are 4 X 5 inches at top; all posts are 5 × 6 inches at bottom. One-half small single load † of sand required per barrel of cement; one small single load of screened gravel or stone required per barrel of cement. Proportion: part "Atlas" Portland cement; 2 parts sand; 4 parts gravel or stone.

Methods of Fastening Fence to Posts. Various methods of fastening the fence to the post are in use at the present time, a few of which follow.

FIG. 45.

Method of Fas

tening Fence to Post.

Removable pins in the moulds form holes through the concrete posts, which holes receive long wire staples which clinch at the back of the post. These staples can be replaced at any time.

Another method consists of a tie wire passed around the post and then twisted tightly around the longitudinal fence wire. This method would appear to be particularly satisfactory where the face of the post is corrugated.

A variation of the above in which one continuous binding wire is used instead of a number of short pieces.

The advantage of this and the above method is that the position of the ties does not have to be determined in advance, but may be readily shifted to suit any position of the fence wires.

In another method, holes are made in the concrete into which wires are inserted. These wires

* From "Concrete Construction Around the Home and on the Farm," published by the Atlas Portland Cement Co.

are then carried to the front of the post and wrapped tightly around the fence wire.

In the "Monarch" Fasteners and Spring Steel Staples, the fastener is inserted in the post while same is being manufactured.

The staple is inserted in the fastener by means of a pair of pliers made especially for the purpose.

The "Tautwire" Fence fastener is moulded into the post when

TABLE XV.-QUANTITY OF MATERIAL FOR CORNER POSTS.* One-half small single load of sand required per barrel of cement; one small single load of screened gravel or stone required per barrel of cement. Proportions: I part "Atlas" Portland cement to 2 parts sand to 4 parts gravel.

* From "Concrete Construction Around the Home and on the Farm," published by the Atlas Portland Cement Co.

same is being manufactured. To hold the fence a common wire staple is driven into the fastener.

In all wire fences considerable tension must be put on the wires if a satisfactory fence is to result. To resist this tension occasional fence posts should be braced, and in no case should this bracing be omitted at the corner posts, and the post in many cases should be made heavier than the posts in the rest of the fence.

SECTION IV

PRINCIPLE OF DESIGN AND CONSTRUCTION IN REINFORCED CONCRETE

CHAPTER XVI

ESSENTIAL FEATURES AND ADVANTAGES OF REINFORCED CONCRETE

REINFORCED Concrete is the term applied to that combination of concrete and steel wherein each element of the combination lends a helping hand to make up for the deficiency in strength of the other. The proverb that "In Union There is Strength," was never more exemplified than in the combination of two materials, different in so many respects yet acting together as a unit in resisting any influences that tend to disrupt the structure built therefrom.

Beginning with the building of flower pots by a French gardener 40 years ago, the business of reinforced concrete had a haphazard growth for over twenty years, owing to unfamiliarity with the nature of the materials, distrust on the part of consumers and antagonism of union labor. Through the establishment of safe, rational, and scientific methods of design, made possible by tests and studies carried on consistently by men like Melan, Hennebique, Ransome, Considère, Hyatt, Thatcher, Thompson, and others, confidence has given place to distrust and what only ten years ago was looked upon with suspicion is now hailed as a blessing. The fire at Baltimore and the earthquake and fire at San Francisco have removed the last lingering doubt, and constructors are now agreed that in point of fireproofness, and the ability to withstand severe shock and strains, reinforced concrete has no equal among structural materials.