CONCORDAT 



changed to the "Parish of Concord" in 1765, 

 and the town was incorporated in 1784. In 

 1808 it became the state capital, and was in- 

 corporated as a city in 1853. W.W.T. 



CONCORDAT, kon kawr'dat, in the affairs of 

 the Roman Catholic Church an agreement be- 

 tween the Pope and a secular government for 

 the settlement and regulation of affairs of the 

 Roman Church within that state. It may be 

 proclaimed in the form of a Papal bull, or 

 edict, or it may be by formal treaty. There 

 have been many famous concordats in history, 

 but as the principle of the separation of Church 

 and State has gained ground such instruments 

 have become of less importance; the denuncia- 

 tion of a concordat by a nation does not neces- 

 sarily entail the separation of Church and 

 State in that country, or the rupture of diplo- 

 matic relations with Rome. See TREATY. 



1526 CONCRETE 



Another combination also recommended is 



1 part cement 



3 parts sand 



6 parts gravel or crushed stone. 



The former mixture is suitable for reinforced 

 concrete, the latter for ordinary work. The 

 amount of water varies from about one-sixth 

 to one-fourth the volume of the mixture; that 

 is, four gallons of dry mixture would require 

 about one gallon of water. The strongest con- 

 crete is that in which each particle of sand is 

 surrounded by cement and all the space be- 

 tween the pieces of stone filled with cement 

 and sand. 



Concrete is of a grayish color. When a 

 smooth finish is desired it is covered with a 

 mortar of one part cement and two parts sand. 

 Concrete hardens or "sets" in a few hours, but 

 does not reach its full strength until about two 



A CONCRETE VIADUCT 



This structure connects Pasadena, Cal., with San Raphael Heights. It Is 1,476 feet In length, and 

 the highest span Is 148 feet above the valley below. The cost was nearly $250,000, and It was a year 

 and a half in building. 



CONCRETE, konkreet' , an artificial stone 

 which is now being largely employed for a 

 great variety of building purposes, from tall 

 business blocks and mammoth factories to fine 

 residences and to bridges and culverts. It is 

 made by mixing sand, Portland cement and 

 gravel, crushed stone or cinders and adding 

 sufficient water to wet each particle. For some 

 purposes enough water is added to reduce the 

 compound to the consistency of mortar, but 

 if the mixture is too wet the heavier particles 

 will sink and the lighter ones rise to the sur- 

 face, giving uneven strength to the concrete. 

 The cement binds the other materials together 

 in hardening and forms them into a strong, 

 durable stone. The proportions most gener- 

 ally used, especially for what is known as rein- 

 forced concrete, are 



1 part cement 



2 parts sand 



4 parts gravel or crushed stone 



years after it is laid. After this time it retains 

 its durability and hardness, and for most pur- 

 poses it is more lasting than natural stone. 

 The strength and durability depend upon the 

 quality of the materials used and the care with 

 which they are mixed. Crushed stone makes 

 a stronger concrete than gravel, because the 

 cement, owing to its flat, unpolished surfaces, 

 can bind it more firmly. A poor grade of 

 cement or dirty sand makes a weak concrete, 

 and the best material, when poorly mixed, 

 makes an unsatisfactory product. Concrete 

 should never be made in cold weather. 



Concrete Construction. Concrete is so easily 

 adapted to all sorts of building purposes that 

 within the last few years its use has been 

 widely extended. The farmer can have con- 

 crete foundations for his buildings, concrete 

 graneries, which are fire and vermin proof, and 

 concrete fence posts, if he desires them. 



Engineers are now using concrete for the 



