THE COTTAGE GARDENER AND COUNTRY GENTLEMAN, Ejebmurt 1, I860. 
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strength of small beams, girders, or purlines, much more 
than that of girders of any practical dimensions whatever. 
A square log, of eighteen inches on the side, placed as 
breastsummers,—technically, “ brace-hammers,”—would 
hardly carry more weight, securely, than this kind of 
truss, which is fastened at both ends, near the upper 
corners of the two ridge boards, by nuts'and screws. 
From the shoe, or fastening points (t and si, fig. 4), the 
iron truss comes down to the lower edges of the nine-inch 
boards, each at one-third the length of the ridge ; and 
then two iron bolts, an inch thick, are 'put between the 
upper edge of the iron-bar truss and the, two lower edges 
of the ridge board. The nut is then screwed on to the 
end of the truss, at si, and turned till the pressure of the 
centre of the truss against the two cross bolts is strong 
enough, to hold up the ridge. The ridge is then capped, 
and you see nothing but the plain bar just outside the 
lower edge of the ridge in the middle—the part which 
is left out in fig. 4, to give room. 
Various ways of applying this suspension trussing are 
given in Herbert’s “ Engineer’s and Mechanic’s Ency¬ 
clopedia,” vol. I., pp. 158—161; but Mr. Macrostie is 
the first who has applied it successfully to the ridges of 
span-roofed houses, so as to need no support. The rest 
of fig. 1, such as the side walls, is in one half wood and 
the rest glass. The fancy ridge finish, and the style of 
the end, tell their own tale ; but any one may alter them 
to suit his own taste, without infringing on the principle 
of construction. 
Fig. 2. The section of the same house, and the only 
part wanting explanation. The lights are here seen in 
the usual way—the short ones (f f) at the top, to slide 
over the long one. But that is not the way at all. There 
is no sliding: the upper part of the short light is hinged 
to the ridge, and it opens up by a cord over a pully. All 
the short lights on one side might open with one more, 
on the principle of sympathetic movement. These short 
lights are only three feet, and the sides of the bottom 
lights run up under them to the ridge, where they are 
fastened. When they are putting up one of these roofs, 
the ridge is the first thing fixed; then all the bottom 
lights, without the ventilator lights. The sides of the 
lights stand one inch apart all over the roof—that is, the 
side of light No. 2, stands one inch apart from the side of 
No. 1. That inch opening is where the rafter ought to be, 
and there is such an opening where each rafter should be. 
In the section, you only see one side of light No. 2, and 
the one which corresponds with it on the other side of 
the span. Each of these sides looks like an archer’s bow, 
the string being the side of the light—the upper line, 
and the bow is bent in the line n. From the bow, it, to 
the string are two cross pieces, or legs. At the bottom 
of the bow, at d (tho same as m, fig. 4), is a screw, and the 
top, at f (or l, fig. 4), is an eye. n is the truss rod, which 
is only half an inch in diameter, but does the work of a 
rafter. The top and bottom of the truss rod come in be¬ 
tween the sides of each of the two lights, and arc fastened 
there, at the top, by means of the eye. An iron bolt, 
half an inch in diameter and three inches long, passes 
through the eye, and enters a hole in the side of each 
light; and the bottom being a screw, a nut is worked on 
it, which nut embraces the bottoms of the two lights. 
Then, by screwing up this nut, the rod (n) is brought to 
a tension, or full stretch, and the two cross bolts, or legs, 
from it, press up agamst the sides of the light by means 
of a T end. Now, screw up the nut, and these two legs 
will push up the sides of the lights to the right pitch of 
a rafter, or higher still, till the sides of the lights break, 
if they yield before the truss rod would snap by the 
tension. When the truss rod is stretched to the right 
pitch for the lights, any extra weight put on the roof,— 
say, a deep fall of snow from above, or an enormous crop of 
Grapes from below,—the effect on the roof is the opposite 
to that which would affect a rafter : an extra weight 
would cause the rafter and the lights to sag,—technically, 
to deflex,—but an extra weight on the truss would cause 
the roof to heave upwards. A span roof, or a lean-to roof, 
thus trussed, will not cause a sideways pressure to the 
walls, or glass sides, on which it is placed: it will not only 
not cause lateral pressure, but by fixing it with screws, one 
in the middle of each light, to the plate, at d, it keeps the 
sides, either on the perpendicular, or at an easy angle, if 
that is required. The power of the truss is perfectly 
astounding, when compared with the size of the truss 
rod. Place a lath between two chairs, and a weight of a 
few pounds, put on the middle, will break it, because both 
ends are free ; but block up, or nail, the two ends, and it 
will require from twenty to thirty times the weight put 
on it to snap it: that is the first degree in trussing. Now 
join the two ends of the lath by means of a truss like 
ours, and put two short pieces (as at n, fig. 2) at the 
“ necessary points,” and the lath will carry 400 times the 
weight. The “ necessary points ” are as essential to 
know as the property of the truss. 
For all practical purposes, in hothouse building, the 
length of a truss should be in three equal divisions. 
They are all so at the Crystal Palace, every part of 
which, galleries, girders, ridges, valleys, and all about 
it, are on the trussing system, which is the secret of 
its enormous strengh against all weathers. Every truss 
about that Palace is twenty-four feet long, in three 
divisions of eight feet each; then eight and sixteen 
are the “ necessary points” for the legs, or cross-pieces,—- 
as seen, at n, in our section,—for their trusses. And so 
with ours, and all in our line. Thirty-four feet, I believe, 
is the longest length that Mr. Macrostie has yet done 
in trussing, without a truss: that is the exact length 
of Messrs. Jackson’s new trussed-house. That house 
is twenty-two feet wide, and the roof rests on two old 
walls, which would bulge out at the least lateral strain ; 
but the pressure of the trussed roof falls so perpendicularly 
upon them, that they cannot budge from under it. The 
truss rods for that house are not more than half an 
inch in diameter, and the ridge i3 in two flitches, or 
boards, an inch and a half thick, and nine inches deep, or 
wide, just the same as in the house of which the view 
is given. That house is at Surbiton, but I must not 
say where, as, although our readers arc respectable 
people, some others might hear of it who have brass 
enough to truss a pyramid; and they would be sure to 
bother the owner of the house to death, asking to see 
it, every hour of the day, and every day in the year, 
Sundays and all. But, supposing the virtue of one truss 
to end at thirty-four feet,—I put it at forty on scale, 
the length that is proved,—still we can double thirty- 
four, and have no prop for the ridge in portable houses. 
Surely, another such house of thirty-four feet stretch, 
placed against the end of the one in Kingston Nursery, 
would stand, and bo as firm as the present one. Then, 
you have a house sixty-eight feet long, and twenty-two 
feet wide ; but you may rely upon one seventy feet long, 
and thirty feet wide, if that is a comfort on “flitting 
day,” as they say in Dingwall, when a tenant is leaving 
a place. You may place it on the green sward, or on 
wheels to go that way from place to place, or, better 
still, on a stretch of rail instead of a sill. I once saw a 
house of about that size going and coming on rails, just 
like a locomotive engine. It was a wooden house, 
thatched, to run off and on, for covering an Orchid- 
house, at Cliatsworth, and Mr. Eyles, who is now at the 
Crystal Palace, was the guard on that occasion. 
The gardeners at the Experimental Garden are de¬ 
lighted with the new houses there, which are fixed,but with¬ 
out anything in the way of stays across, or supports, to 
keep them from tumbling down. One house, the new 
greenhouse, is a double house, and a lean-to, if that can be 
understood. But this is how it : s. It leans against the 
back wall of a house belonging to the offices, but the 
office of which is removed elsewhere : tnat house stands 
to the north aspect, and was tho principal house for 
