134 Mr Russell on the Construction of Buildings 



the line AX must fall below AY, so as to leave the space 

 Y a:' = 18 inches =Zy. 



Let us now apply this formula to every individual place in 

 the room or interior of the building, and we shall have the form 

 required to satisfy the auditors. Let vis also assume 2^ feet as 

 constant, and as representing the distance of one spectator behind 

 the other measured horizontally, and 1^ feet as the clear space, 

 measured on the vertical line for the mean range of comfortable 

 vision for each. If the level of the floor, that is of the lowest 

 seats, be already determined, the form of the interior accom- 

 modation may be thus described. AY, the height of the 

 speaker; YX, the level floor. From At/ take Y^=:4feet. 



Fig. 2- 



3 4 5 6 7 8 X 



Draw yx parallel to YX. Take Ay to ycc as 1;^ to S|, that 

 is, as h, the range of position of the spectator, to d the distance 

 between the seats. Take horizontal distances 1,2, 3, 4, &c. 

 = 2A feet; prolong A.r toa^i, then the height .r, to Z= 1| feet. 

 Join Al and ])rolong it to x-j, and take a distance a.2 to m z= 1 ^ \ 

 through m draw A m, and prolong it x^, and take 5^3 n= li 

 feet ; through n draw A 71, prolong it to x^, and take XiO = 1^ 

 feet. Continue this process on in the same manner to p, q, 

 r, s, t, &c., and you will find points which are the successive 

 places which the heads of the auditors should occupy. The 

 bottom of the seats must rise by the same quantity. 



But it is not only in receding that the back seats must rise; 

 we have already noticed that the seats which are too far forward 

 are also unpleasant, — they are too low ; they also should be 

 raised, but this must be done so as not to interrupt those who 

 are behind. This, too, may be accomplished in a similar way ; 

 for, as formerly set off, 1, 2, 3, 4, 5, 6, &c.=: 2^ feet. 1 is the 



