i:\TKKlN. : 



IUL CRIMINAL COURT. 



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bridge executed of Ute years, the engineer, Mr. Harrison, mp|>orted 

 the centra by means of four temporary piers erected in the water wy 



' J 



Centre of Chester Bridge. 



of the river ; and he was thus enabled to place the struts of his fram- 

 ing o aa to receive the whole of the weight thrown upon them, in a 

 direction but slightly oblique to their axes. Telford, in erecting the 

 Gloucester bridge, did somewhat the same thing, for he supported his 



Centre of Gloucester Bridge. 



centre* upon intermediate pile* driven into the bed of the river ; and 

 the engineer of the great bridge over the Dora Riparia, at Turin, intro- 

 duced an intermediate support in the modification of the Ncuilly 

 centre he employed. In fact the danger of subsidence in a centre of 

 large span must be so great, that the greatest precautions must be 

 adopted to guard against it ; and as such precautions necessarily in- 

 volve great money outlays, it iniut evidently be preferable to diminish 

 the necessity for them by diminishing the opening to be temporarily 

 spanned. The execution of such triumphs of engineering skill as the 

 centres of London Bridge, is too costly to bo repeated of tenor than 

 may be absolutely necessary. 



In Kontana's great work, published at Borne, 1694, ' II Tempio 

 Vatican'),' the centre* used by Michel Angelo for the execution of 

 the dome, and of the long vault* of that building, are very faithfully 

 given in the plates opposite pp. 820 and 412; and they may still be 

 referred to as models notwithstanding the progress of modern science, 

 and even notwithstanding Dr. Kobison's faint praise. In the con- 

 struction of part of the dome of the Pantheon of Paris, Rondelet made 

 every ring of voussoirs complete in itself , so that the centre he em- 

 ployed, which is given in his ' Art de Batir,' Paris, 1848, had but, 

 comparatively speaking, little to do in supporting the weight of the 

 masonry, in those portions at least ; but when the rings of vouseoirs 

 war* interrupted to receive the openings of the windows, a more com- 

 plicated centre was required. The reader would do well to study this 

 portion of Kondalet's work, for it contains SOB* of the most valuable 

 practical aad scieaoUc reasoning, on the aetioa of arches upon their 

 centres, to be found in uy existing work OB architecture: excepting, 



perhaps, the first volume of Robison's 'System of Mechanical 1'liilo. 

 sopliy,' Edinburgh, 1822. 



It has been already mentioned [BRIDGE], that the system < 

 porting the extremities of centres had been, until a very recant period, 



Centre of Viaduct on Grand Junction Railway. 



to place them upon a series of wedges, which wi-re diiveu hack when 

 it was tin Right advisable to release the arches ; and in the cases of 

 London, Blackfriars, and Waterloo bridges such wedges were used. 

 But it often happens that the grains of the woods used for the wedges, 

 and the inclined ways, are driven l>y the superincumbent load iuto one 

 another to such an extent that it is not possible to move them; and 

 under such circumstances, it has occasionally been found necessary to 

 cut away the points of support of the centres, an< ! m full, 



perhaps, abruptly. Even when the wedges move, the blows they 

 require are likely to jar the masonry ; and it was with a view of 

 obviating this serious practical evil that the use of the sand-bags, 

 described as having been applied on the Tours and Bordeaux Railway 

 bridges (in the ' Annals des Fonts et Chausse'es '), was introduced. It 

 seems, however, that there are occasional difficulties attending the dis- 

 charge of the sand from the vessels placed at the feet of the centres ; 

 and as under any circumstances it is preferable to employ centres with 

 intermediate points of support, added subsequently to the placing of 

 the great framing resting upon the springing^, it may be sufficient to 

 trust to the loosening of the centres by the gradual removal of the said 

 intermediate supports. 



In small centres, in centres for brick, concrete, rubble, or groined 

 arches, the frames, which are usually spaced at intervals of about live 

 feet, are covered with what is technically called " close boarding ; " in 

 centres for large openings, wherein ashlar masonry is employed, the 

 courses of stones are supported upon " laggings," placed at right 

 to the axis of the structure. In both cases precautions must be taken 



nt .my lateral movement of the frames or trusses by !>< 

 iluetion of a system of cross braces, which should be designed in such 

 wise as to distribute the partial weights in as general a manner as 

 possible over the whole system of framing. 



In addition to the works quoted above, see Tredgold's ' Kl. 

 Principles of Carpentry,' Lond., 1840; Kmy, 'Traitc de la cl 

 terie,' Paris, 1841; Kraft, ' L'Art <le l.-i ( 'liarponte,' Paris, 1805; 

 Sillowayji ' Handbook of Modern Carpentry,' New York, 1868. 



CENTIGRADE means divided into one hundred degrees. The 

 centigrade thermometer of Celsius divides the interval between the 

 freezing and boiling points into 100 degrees. Thus 100 centigrade 

 degrees are equivalent to 180" of Falir. ; and to turn the reading of a 

 centrigrade thermometer into that of Fahrenheit, proceed as follows : 

 Multiply by 2 and 20, subtract, divide by 10, and add W. Tl. 

 78 centigrade 



78 

 2 



166 

 1560 



1404 . . . 140-4 

 82 



172-4 Kahr. 



CENTRAL CRIMINAL COURT. This is a court established in 

 1884, by 4 & 3 Win. IV. c. 80, for the trial of Irea/wim, murders, 

 felonies, and misdemeanours committed within the city of Lond< 



n| Middlesex, and part* of Essex, Kent, and Surrey. By . 22 



