568 
Implement Shoio at Manchester. 
covering should be compared as to durability and cost with that of irou and 
felt, in order to explain the grounds of the adjudication of the second prize of 
5Z. to the felt roofing in preference to that of iron. Slate roofing being familiar 
to all persons, it is unnecessary to describe the mode of construction adopted 
by Mr. Jackson, which professes no specialty. The cost per square of ground 
covered (10 feet by 10 feet) may betaken at .5Z. Os. lOd, or rather over Is. per 
foot. Messrs. Morton's example of galvanized corrugated curved iron roofing on 
wrought iron framing was tied together by the ordinary wrought iron rods 
with king-post-rod and key. The cost per square of ground covered is stated 
to be 3?. 18s., or nearly ^\d. per foot, including wall-plates. Tiie felt roofing of 
Messrs. McTear and Co. of Belfast, was in the form of an arc of a circle, of 
^vhich they state the pitch should be Ij inch per foot, preserved in its shape 
by a girder formed of " bows and strings," with lattice work between them 
tied by a solid web of timber equal to one-fifth of the span, to give extra 
strength to the bearings. These lattice girders are from 8 to 10 feet apart ; 
on these are purlins 22 inches apart, covered with a sheeting of half-inch 
boards in long lengths, and from 9 to 15 inches broad, upon which is laid the 
felt, which is again covered with tar or varnish properly prepared. Messrs. 
McTear and Co. state that they have covered spaces 75 feet in width with 
perfect satisfaction, and will undertake to cover a width of 100 feet without any 
intermediate supports. The cost per^square of gi'ound covered, including wall 
plates, is stated to be 11. 12s., or nearly 4(i. per foot. The period of durability of 
slate roofing may be stated to be at least fifty years, that of iron twenty-two 
years, and that of felt eight years ; the first requiring no other act of mainte- 
nance than ordinary repairs, the second requiring strict attention in painting 
to preserve it from the corroding effects of uprising vapours, and the third, in 
addition to repairs, requiring a coat of tar or prepared varnish every other year 
to preserve it from the effects of the sun and weather. The question of 
economy is not therefore determined by the first cost, but must have special 
reference to the periods of duration of each description of material ; for as the 
roof will require to be replaced at the termination of each period, it is necessary 
that the principal money first expended should be repaid within such periods. 
The true state of the case as respects economy will be understood, therefore, 
by comparing the annual amounts per square of ground covered, which must 
be gained to repay the cost within the periods mentioned, and calculating the 
value of money at 5 per cent, interest they are as follows : — 
Each is liable to ordinary repairs, iron and slate requiring very little indeed, 
and felt requiring more. 
Tliatch-suhsiitute. — Messrs. Morton and Co. exhibited a very ingenious 
arrangement for the use of galvanized corrugated iron for covering hay and corn 
stacks, which they have named the " Thatch Substitute." The corrugated cover- 
ing is made in slieets of difierent lengths and widtlis, the width varying from 2 
to 2^ feet, and the length accoi-ding to the size of the stacks in ordinary use, 
two lengths extending from ridge to eave. It is intended that all the sheets 
required for the covering of a stack should be of one size, and capable of being 
packed in a box and stored away. They arc connected together by twisted- 
iron lashing-cords threaded through eye-bolts, which connect the sheets with 
longitudinal strips of wood, which are laid on the stack where the covering- 
sheets join. Along the ridge there is galvanized capping, which is connected 
also by the same eye-bolts through which the cord runs. The cords arc long 
enough to reach to the ground on each side of the stack, where they are 
fastened to anchored winders, which strain the cords and keep the whole tied 
Slate 
Iron 
Felt 
s. d. 
5 6 
5 10 with painting once in 3 years. 
4 11 with tarring once in 2 years. 
