4JI 



PERSri.l'MUIIYnHOCYANIC ACID. 



rr.isrviAX 





projection of a, to this transferred vanishing point, will cut / pro- 16S. Drew line* through I' and through the ohli.pie j.r.." 

 doo*d in /', the oblique projection of the luminary on the plane of the a', V, c, if. S, *<-., inU-mecting each *uch line by tin- luminous ray 

 shadow, 'a, *t, *r, 4c., in the ahadowi a", V, e", &c., of the angles of the cube, 



O* ,< PI 



and these points being joined, the figure thus produce'.! will be the 

 image of the shadow of the cube on the plane as proposed. 



164. The oblique projecting lines a a', tc., were assumed parallel to 

 the picture and its auxiliary plane, simply for facility of construction, 

 or else the points a, b, r, r,f, &c. t might, as well as the luminary, hare 

 been projected on the plane of the shadow by lines in any direction, 

 provided these lines were parallels according to the above principle 

 (158). 



165. Draw lines through * and p., p,, and <J, the vanishing points of 

 the sides of the cube; then the images, as a"b", c"d", e"jT, of the 

 shadows of the parallel lines of the original solid will meet in a point 

 in the corresponding line drawn through * and the vanishing point of 

 those originals. For the planes passing through * and the parallels 

 ab, ed, /, ftc., must intersect in a common line, passing through * 

 and parallel to those originals : this common intersection will there- 

 fore have the game vanishing point, p,, as those originals ; the line * p, 

 represents that common intersection. Now the shadows a" l>", cfif, e"f" 

 are the intersections of the before-mentioned planes by another, namely, 

 by the plane of the shadow, and these intersections, a"6", c f 'd" f &c., 

 must meet each other in a point in * p, the common intersection of the 

 plane* pasting through * and the original lines. The same reasoning 

 applies to the other shadows of the corresponding parallel sides of 

 the cube. 



PER8ULPHOHYDROCYANIC ACID. Synonymous with hydro- 

 pemdphoryanic arid. [CYANOGEN.] 



PEBSULPHOMOLYBDKNIOlCID. [HOI.TBDEXUH, Sulphide* o/.] 



PBBTURBATIOXa [URAVITATIOX.] 



PKRTUSSIS. [Hoopl.xo-CouoH.] 



PERUVIAN A1JCHITECTURE. Uemains of ancient Peruvian 

 buildings are dispersed over the western parts of South America, from 

 the equator to 15* S. lat., especially over the Montana. Nothing 

 certain w known of their date, but the oldest is attributed to Man 

 Capac, the tnulition.il founder of ancient Peruvian civilisation, who 

 b said to have flourished about three centuries before the conquest of 

 Pern by the Spaniards, or 1 200 A.D. These remains are characterised 

 by simplicity, symmetry, and solidity. There arc no columns, pilasters, 

 or orchen, and the buildings exhibit a singular uniformity and a com- 

 plete want of all exterior ornaments. The structures, whether mere 

 walls or buildings, are all of stone ; the blocks in some instances being 

 squared and laid in horizontal courses, in others consisting of huge 

 polygonal ma*ms; whilu in Imth the doorways and openings for 

 light are formed of jambs inclined toward* the top, and covered with a 

 large stone as a lintel ; being, in foci, in all respecU almost the exact 

 counterpart of the Pelasgian masonry of Greece and Italy [PKI.ASOIAN 

 ARCHITECTURE] a circumstance the more remarkable since, if Peruvian 

 tradition be not altogether at fault, some eighteen centuries must have 

 elapsed between the latest example of Pelugio construction in Europe 

 and the earliest in Peru. 



The great road of the Incas, which runs from Quito to Cuzco and 



the table-land of the Ucsaguadero, \n made of enormous masses of 

 porphyry, and it is still nearly perfect in several parts of the Moi 

 Humboldt obtained an ancient Peruvian cutting instrument, which 

 had been found in a mine not far from Cuzco : the material consisted 

 of 94 parts of copper and 6 of tin, a composition which rendered it 

 hard enough to be used nearly like steel. With instruments made of 

 this material the Peruvians cut the enormous masses of which their 

 buildings were composed. Some of the buildings near Cuzco contain 

 stones 40 feet long, 20 feet wide, and nearly 7 feet thick. These 

 stones are fitted together with great skill, and, as it was supposed, 

 without cement. But Humboldt discovered in some ruins a thin layer 

 of cement, consisting of gravel and an argillaceous earth; in other 

 edifices, he says, it is composed of bitumen. These stones are all 

 parallelopipedons, and worked with such exactness that it would be 

 impossible to perceive the joinings if their exterior surface were quite 

 i level ; but being a little convex, the junctures form slight depressions, 

 which constitute the only exterior ornament of the buildings. The 

 doors of the buildings are from 7 to 84 feet high. The sides of the 

 1 doors are not parallel, but approach each other towards the top. The 

 niches, of which several occur in the inner side of the walls, have the 

 j form of the doors. 



The walls of Cuzco are formed of huge polygonal blocks of limestone, 

 from 8 to 1 feet in length, and the same in width, and admirably 

 fitted to each other without cement, precisely like those shown in the 

 cut of the Walls of Epirus in PKI.ASGIAN ARCHITKCTUBE ; but it is 

 remarkable that not only is the masonry almost perfect of its kind, 

 but that the walls are planned as fortifications with a degree of skill 

 that excites the highest admiration of the military engineer. 



The oldest known building in Peru is that called the house of Manco 



Canac, which stands on an island in the lake of Titicaca. It is built of 



rather small irregular polygonal blocks of stones ; is curvilinear in plan 



and has small rude towers. The interior is divided into small square 



' rooms, which are lighted only from the doorways. Not far fnun it in 



j a later and less rude building of two stories, known as the House 



j of the Virgins of the Sun. It is nearly square in plan, ami is 



1 divided into twelve small square rooms on each story, those on 



1 the ground-floor being lighted by the doorways, and those- 



mostly by very narrow windows, but some are without any opening 



or li ght. 



Th most extensive Peruvian buildings occur in the table-land of 

 Cuzco, which was the most ancient scat of the monarchy of lh< 

 There are also ancient remains within the boundaries of the | 

 lepublii-of I'ViM.lor. Near the ridge called Chisinelie. not. f... 

 the volcano Cotopaxi, are the ruins of a large buildin ; 

 Palace of the Incas. It was a square, of which each side was 

 80/yards long, and it had four doors. The interior was divided into 

 eight apartments, three of which are etill in tolerable i 

 Not far from the mountain-pass of Assuay is a building called Ingap. 

 pilca, or the Fortress of Canar, consisting of a wall of very large stones, 



