50
ly difficult in the tropics to maintain such roofs watertight,
exposed as they are to extremes of temperature.Guttering and
down pipes should be designed for excessive falls of rain, on
one occasion three inches an hour for three consecutive hours
has been measured in Hong-Kong, and, sixteen inches in 7 hours
and 27 inches in 24 hours.
13. Granite of excellent quality is plentiful
in the Colony, and though the cost of dressed granite masonry
is about double that of brickwork, it would be desirable to use
the former largely for the facing at least of the buildings.
14. Special material for the covering of the
dome will have to be obtained from England and should he de-
signed and specified by the architects.
15.
The thickness of tiled roofing including
the row of mortar with which the joints of the adjacent rows
of tiles are covered is 9 inches. The tiles are 9 inches wide
and the common rafters or battens on which they are laid are
spaced 9 inches centre to centre. The weight of the tiling
when wet is 42 lbs per square foot and when dry 31 lbs.per
square foot. The strength of the timber, such as would he used
for purlins or common rafters is nearly equal to that of teak
as given by Molesworth in his value of K (co-efficient of rup-
ture) for rectangular heams,
(98.) R.D.ORMSBY,
16.11.98.
Dir. of Public Works.