Hollow Brick Roofs. 
183 
cutting tlicm deep into the slone springers, and bedding them 
in the same with Portland ce- 
ment ; tlie opening made in the 
stone should fit correctly the 
external outline of the triangle 
on the end of the tie-rods. The 
tie-rods may be placed from 6 
to 10 feet apart, according to 
circumstances. 
In the section of arch with 
stone springing, thb parapet and inside gutters are dispensed 
with, and may be so with stone ; but with the cast-iron spring- 
ing, the parapets and inside gutters are indispensable. 
The gutters inside the parapets are formed with Portland 
cement, and made with a fall of 6 inches to the outlet. A fall 
of 6 inches might suffice for a length of from 40 to 50 feet, 
wliicli would require only one down-pipe for the water, for from 
80 to 100 feet. 
mi 
Mi 
1.0N(;iTUUINAI, SECTION. 
Twelve incliCB long. 
SECTIONS OF HOLI,OW BRICKS. 
