7^9 



PLATE XII. 



Fig. 156, The middle areh of Black Friars Bridge, 

 P. 164. 



Fig. 157. A spherical dome, of wliich the lower 

 parts are made thicker, in order that they may be of 

 equal stability throughout. From A to B the dome is 

 of equable thickness : below C and D the thickness can-* 

 not be increased sufficiently to procure an equilibrium, 

 without the application of a chain or hoop, of which 

 tlie section is represented at C, D. If the thickness 

 .were not at all increased, a hoop would be required 

 at E, F, or still higher. P. 165. 



Fig. 158. A section of the roof of St. Paul's Cathe- 

 dral. The section of the dome consists of two circu- 

 lar arcs, of which the centres are a little beyond the 

 axis: it is supported by carpentry, resting on a cone of 

 brickwork. The internal dome is of brickwork only, 

 ■ and is open at the summit. P. 165. 



Fig. 159. A section of the dome of the Pantheon at 

 Kome, P. 165. 



Fig. 160. A Tuscan column, with its pedestal, capi- 

 tal, and entablature. P. 165. 



Fig. 161. A Doric column. P. 165. 



Fig. 162. An Ionic column. P. 165. 



Fig. 163. A Corinthian column. P. 165, 



Fig. 164. A Composite column. P. 165. 



Fig. 163. An elevation of the end of King's College 

 Chapel, Cambridge; showing on one side the buttresses, 

 the tower being supposed to be removed, and on the 

 other the tower, which not only supplies the place of a 

 buttress at the end, but assists also in supporting a 

 considerable portion of the thrust in the direction or 

 the length of the chapel ; the roof, which is of stone, 

 being vaulted in this direction as well as tranversely. 

 There is also a roof of carpentry, covered with lead 

 above the stone roof. P. 166. 



