B R I 



479 



B R I 



this substance, either baked or unbaked, float in 

 water ; and a twentieth part of argil may be added 

 to their composition without taking away their pro- 

 perty of swimming. These bricks resist water, unite 

 perfectly with lime, are subject to no alteration from 

 heat or cold, and the baked differ from the unbaked 

 only in the sonorous quality which they have acqui- 

 red from the fire. Their strength is little inferior to 

 that of common bricks, but much greater in propor- 

 tion to their weight ; for M. Fabbroni found, that a 

 floating brick, measuring 7 inches in length, 4>\ in 

 breadth, and one inch eight lines in thickness, weigh- 

 ed only 144 ounces ; whereas, a common brick weigh- 

 ed 5 pounds 6| ounces. The use of these bricks may 

 be very important in the construction of powder 

 magazines and reverberating furnaces ; as they are 

 such bad conductors of heat, that one end may be 

 made red hot, while the other is held in the hand. 

 They may also be employed for buildings that re- 

 quire to be light ; such as cooking places in ships, 

 and floating batteries, the parapets of which would 

 be proof against red hot bullets. The turrets which 

 were raised on the ships of the ancients, says M. 

 Fabbroni, were perhaps formed of these bricks ; and 

 perhaps they were employed in the celebrated ship, 

 sent by Hiero to Ptolemy, which carried so many 

 buildings, consisting of porticoes, baths, halls, &c. 

 arranged in mosaic, and ornamented with agates and 

 jasper. 



Bricks appear to be of the highest antiquity ; 

 and, as we learn from sacred history, the making of 

 them was one of the oppressions to which the chil- 

 dren of Israel were subjected during their servitude 

 in Egypt. The bricks of the ancients, however, so 

 far differed from ours, that they were mixed with 

 chopped straw in order to bind the clay together, 

 and instead of being burned were commonly dried in 

 the sun. Vitruvius recommended, that they should 

 be exposed in the air for two years before they were 

 used, as they could not be sufficiently dry in less time ; 

 and by the laws of Utica, no bricks were allowed to 



be used, unless they had lain to dry for five years. 

 From Dr Pocock's description of a pyramid in 

 Egypt, constructed of unburnt bricks, it appears that 

 the Egyptian bricks were nearly of the same shape 

 as our common bricks, but rather larger. Some of 

 those he measured were 13* inches long, 6$ broad, 

 and 4 inches thick; and others 15 inches long, 7 

 broad, and 4^ thick. The bricks used by the Ro- 

 mans were in general square ; and M. Quatremere de 

 Quincy observes, that in his researches among the 

 antique buildings of Rome, he found them of three 

 different sizes. The least were 7$ inches square, and 

 1^- thick ; others 1GJ inches square, and from 18 ti. 

 20 lines in thickness ; and the larger ones 22 inches 

 square, by 21 or 22 lines thick. Among the cele- 

 brated buildings of antiquity constructed of brick, 

 were the tower of Babel, and the famous walls of 

 Babylon, reckoned by the Greeks among the wonders 

 of the world ; the walls of Athens, the house of 

 Croesus at Sardis, and the walls of the tomb of Mau- 

 solus. The paintings, which were brought from L.a- 

 cedaemon to Rome, to ornament the Comitium in the 

 edileship of Varro and Murena, were cut from walla 

 of brick ; and the Temple of Peace, the Pantheon, 

 and all the Thermx, were composed of this material. 

 The Babylonian bricks, which are in the possession of 

 the East India company, aud upon which Dr Hayes 

 has lately favoured the public with a dissertation, are 

 inscribed with various figures and characters, and are 

 supposed by some to be a part of that brick work 

 upon which Pliny tells us, that the Babylonians 

 wrote the observations which they made of the stars 

 for seven hundred and twenty years. See Fourcroy 

 et Gallon, Art (lit Tuilicr liriqnctier ; Jars on ma- 

 king Bricks and Tiles; liozier Introduction aux Ob- 

 servations stir la Physique, sur I'Uisloire Nalurelle, 

 et sur les Arts; Bergman's Essays; Nicholson's 

 Journal, vol. ii. p. 498.; Repertory of Arts, vol. iii 

 p. 84. ; and Encyclopedic Melhodiquc. (L.) 



BRIDE. See MARRIAGE. 



BRIDEGROOM. See MARRIAGE, 



Bnck. 



BRIDGE. 



A HERE are few operations of art in which mankind 

 are more deeply interested than in what relates to 

 bridges. The ingenuity and hazard involved in con- 

 structing them ; the numerous advantages derived 

 from them ; their being from objects of utility, in 

 many instances, raised into all the magnificence which 

 science and power can exalt them ; justify us in treat- 

 ing the subject at considerable length, and endeavour- 

 ing to exhibit under one article, most of the material 

 circumstances which are connected with it. 



In order to accomplish this, we shall first, in a 

 cursory manner, trace the history of bridges ; se- 

 condly, state the theory and principles upon which 

 the rules, which ought to guide the engineer, arc 

 founded ; and thirdly, explain what relates to the 

 practice of bridge building. 



HISTORY OF BRIDGES. 



Bridge. 



THE construction of perfect bridges, being a very History, 

 complex operation, cannot have taken place amongst 

 a rude and uninformed people ; and in the course of 

 this discussion it will be seen, that this did not always 

 correspond with the progress of the other arts, even 

 in situations where the intercourse was great. 



The most obvious and simple bridge is that form- 

 ed by single trees thrown across small streams, or, in 

 case of broader streams, by fastening the roots of a 

 tree on each bank, and twisting together their bran- 

 ches in the middle of the stream. These must have 

 frequently occurred by chance, and they fall within 

 the comprehension of the hunter; accordingly Mr 

 Park found even the latter mode practised on rivers 

 ID the interior of Africa. 



