24-feet bay between the columns into three 8-feet bays by half columns of
wood, between which is placed boarding, held in its place by iron clips and
bolts; a plinth, four feet high, is formed immediately above the floor by
frames, filled with what are commonly called louvre-blades, which are hung
on pivots, and of which a large number can be moved simultaneously for the
admission of air; similar ventilating-frames, three feet deep, are
introduced at the top of each storey round the entire circuit of the
building, and by this means a ventilating-surface of no less than 40,800
square feet is obtained, or rather more than one acre.
[Illustration: PORTION OF THE LOWER STOREY OF THE PRINCIPAL ELEVATIONS.]
Externally some light arches are inserted, and open panels form the
inclosure for the upper louvre-frames. The details we have been describing
may be readily traced in the engraving of a portion of the lower storey as
seen from the outside. The exit doors occupy one of the 8-feet bays opening
about six feet wide. The inclosure to the upper storeys closely resembles
those of the ground-floor, but glazed sashes are substituted for the close
boarding, and the plinth is omitted. Each storey is crowned externally with
a cornice and cresting ornament, and over the columns posts are carried up,
to which flagstaffs will be fixed.
To return to the interior. The whole of the floor is boarded; that below is
laid with an interval of half an inch between the boards, to allow the
passage of dust from the millions of feet by which it will be trod; the
gallery floor, on the contrary, has iron tongues between the boards to
prevent the dust from coming through on the heads of the visitors below.
The roof of the transept, which we have described as crossing the building
about the centre of its length, differs from that of the other parts, its
general form being semicircular instead of flat, and rising above the rest
of the building so as to show the whole of the semicircle externally. This
roof is supported by arched timber ribs placed twenty-four feet apart, or
one over every column, which forms a socket, into which the foot of the rib
is fitted and secured by iron straps. Between the ribs, timbers are fixed
which carry minor ribs at a distance of eight feet apart, and upon these
the ridge-and-furrow roofing is constructed in the manner that has been
described for the flat roofing, but following the curve of the arched ribs.
At the springing or foot of the arch on either side of the transept there
is a range of louvre-frames to assist in the ventilation of the building,
and on the top of the arch externally a narrow passage is formed to give
access to the different parts of this roof. On the inner side of the arch
diagonal tie-rods are introduced between the main ribs, which, while they
serve to increase the strength of the construction by tying together all
the parts from end to end, produce an agreeable play of lines forming a
kind of network over the whole of the surface.
The ends of the transept are closed in with fan-like tracery, reminding the
spectator of the magnificent wheel windows of our Gothic cathedrals; this
elegant feature is not visible in our interior view, but will be seen in
some of the exteriors.
There is, perhaps, no part of this interesting building in which the great
size and singular lightness, almost airiness, of the construction are so
strikingly displayed as in the TRANSEPT, inclosing as it does a row of fine
old elm-trees, as if to protect them in their venerable age from the smoke
of the thousands of chimneys that have been gradually forming a destructive
circle around them.
The only portion of solid untransparent roofing in the whole of this
building is formed on either side of the arched roof just described, where
there is a lead flat twenty-four feet wide. This was partly required for a
platform to serve for carrying on the works for the arched roof, and was
also exceedingly useful in giving access to the other roofs on either side;
it likewise afforded the opportunity of giving some additional strength at
the springing of the arched ribs to resist any possible tendency they might
have to spread outwards.
[Illustration: View of the Interior of the Transept.]
[Illustration: View of Glass Roof from the Lead Flat.]
As the weight of such lead roofing considerably exceeds that of the glass
ridge-and-furrow covering, it was necessary at the point where it crosses
the wide span of the main avenue to introduce some stronger roof-girders
than those used elsewhere; of these there are two on either side of the
transept, the inner one of which has also to sustain two of the large
arched ribs with their superincumbent roofing, and its strength is
therefore increased in proportion to the additional load placed upon it.
The extra-strong roof-girders are six feet deep, or twice that of the
others; but their general construction is similar, the diagonal ties
forming a kind of latticework, and thus keeping up the same character.
These, like all the roof-girders of large span, are constructed principally
of wrought-iron. Those who visited the building during its erection, and
were among the fortunate few who were enabled to ascend to the "lead-flat,"
must have been very much struck with the singular appearance presented by
the great expanse of acres of glass stretching in long lines of
"ridge-and-furrow" roofing on each side of the centre, while the eye,
penetrating the transparent covering, became lost in endeavouring to follow
the apparently intricate lines of the interior. Such a view might fairly be
said to justify the title of "Crystal Palace," by which this building is so
commonly known; and it would require no great stretch of imagination to
believe that it had been reared by fairy hands, as a votive offering at the
world's jubilee of labour.
But we must descend again to the interior, to point out the arrangement of
the offices for the staff of the Executive. The principal of these are
naturally placed in the centre, on either side of the principal entrance,
where they occupy in two storeys the space underneath the gallery, which is
continued uninterrupted over them. The entrances at the end are also
flanked by offices of less extent. The outer inclosure of these spaces is
formed with glazed sashes, similar to those which are placed on the
exterior of the building, and boarded partitions divide the interior. The
rooms are arranged to be heated and lighted by gas when required, and ample
means of ventilation are provided.
The simplicity of the construction renders it very easy to extend or
contract the accommodation much more readily than would be possible under
ordinary circumstances.
It now remains to notice the arrangements provided for refreshments, which
are introduced in connexion with the open courts left on account of the
groups of trees. These happen to occur towards the ends of the building,
and on the north side of the main avenue; the space at the north end of the
transept, next to the inclosed trees, is also appropriated for this
purpose. The roofing over these parts is a continuation of that over the
rest of the building; and the partitions necessary for inclosing the
different spaces are formed chiefly with glazed sashes, avoiding as much as
possible any solid construction, which would appear out of character. The
open courts are inclosed with sashes and doors, rendered necessary by the
uncertain nature of our climate.
A small detached building which has not been mentioned serves for the
boiler-house, and is placed near the west end of the building. As it had
been determined to afford the means of exhibiting some of the machinery in
actual motion, it was necessary to erect boilers to supply the steam to the
different machines, as it would clearly be inadmissible for each to
generate steam for its own use in the building. The house to contain the
boilers is ninety-six feet long and twenty-four feet wide, and is placed as
near as practicable to the machinery-department; but at the same time it is
quite detached from the main building to avoid risk from the fires. In
appearance it resembles the one-storey portion of the main building, but it
is constructed entirely of fire-proof materials. It contains five boilers,
each to supply steam for twenty-horse power, which is distributed by a pipe
to the different machinery.
[Illustration: General View of the Building from the South-West.]
An ornamental cast-iron railing designed by Mr. Owen Jones incloses the
building, being placed at a distance of about eight feet from it along the
principal fronts, but carried much further off at the ends, so as to
inclose a considerable space, which will thus be available for exhibiting
any large objects that will bear exposure to the weather, if there should
not be sufficient room in the interior of the building. Gates are placed
opposite all the entrances and exits, and these are so arranged that when
closed they are uniform in appearance with the rest of the railing.
[Illustration: EXTERNAL RAILING.]
Having thus given a general sketch of the arrangement and appearance of the
building, we shall proceed to describe somewhat more minutely the various
details of the construction, of which the essential parts are few in number
compared with the great repetition of each individually. To assist in this
multiplied reproduction of the same form, some exceedingly ingenious
machinery has been employed, which will therefore be described in connexion
with the parts it has been used to form; and thus these will be traced
through their various stages, from the raw material to their finished state
as portions of the building. The greater part of this machinery has been
used in shaping out those parts which are of wood, and particularly the
different portions of the roof, with which we will therefore commence.
The Paxton's Gutters.
It has been mentioned that the rafters which span the space between the
roof-girders serve, at the same time, as gutters, for which purpose they
are hollowed out on the upper face, besides having smaller grooves at the
sides to take the condensation-water. The bottom of the gutter is of a
circular form, which is universally considered the best for conveying
liquids with the least amount of friction, and therefore the least liable
to obstruction from an accumulation of dirt.
[Illustration: SECTION OF THE PAXTON'S GUTTER, WITH THE STRONG SASH-BAR.]
[Illustration: THE CIRCULAR PLANING-MACHINE.]
[Illustration: PORTION OF PLANING-MACHINE, WITH THE REVOLVING ARM AND
CUTTERS.]
A section of the gutter, as finished, is shown. To bring it into this form,
after the timbers had been sawn into the requisite general dimensions they
were brought under the action of the planing-machine, where they were
planed on the four sides. This machine is patented by W. Furness, of
Liverpool, and was worked at the Chelsea Wharf Saw-mills. The operation was
effected by cutters (_a_) attached to the ends of an arm revolving with
great rapidity in a horizontal plane; the timbers to be planed were wedged
up into a frame (_b_) traversing on rails, and as this was passed under the
revolving cutters the upper surface was removed by them, at the same time
the timbers were held down upon the frame by a large iron disc (_c_)
pressing upon their upper surface. The disc, together with the revolving
arm carrying the cutters, was capable of being adjusted vertically to the
exact dimensions of the timber. The traversing-frame was slowly propelled
by the machinery, and three widths of timber were operated upon at one
time. On leaving the planing-machine these quarter baulks were passed on to
the gutter-cutting machine. Four different cutters were required to form
the section, as shown above; they were placed one behind the other, so that
the piece of timber, which was presented to their action above the centre
of motion, passed over each of them in succession. The first set, which
revolved in a vertical plane, roughly hollowed out the larger groove to the
section shown in Fig. 1; the two next were counterparts, and formed the
same section in opposite directions; they were set at an inclination to the
upright of about 45 degrees, the one to the right, the other to the left;
and each hollowed out one of the small side grooves, and one side of the
larger gutter, leaving the section of the timber respectively of the forms
shown in Figs. 2 and 3. Fig. 4 shows the form of its section after it had
passed both; the fourth set of cutters again revolved vertically, and gave
the gutter its finished form, as shown above. As the timber passed over the
cutters it was supported at the ends on revolving rollers, and was held in
its place by guiding grooves, being pressed gradually forwards against the
cutters.
[Illustration: SECTIONS OF THE DIFFERENT STAGES OF THE PAXTON'S GUTTERS.]
[Illustration: THE GUTTER-CUTTING MACHINE.]
In this manner forty-two lengths of solid gutter, each twenty-four feet and
a fraction long, were completed in a day of ten hours; and as the machine
was worked double time, a length of more than 2,000 feet was turned out
daily ready for use: this, it has been calculated, would have required the
labour of about three hundred men to be employed for the same length of
time. The absolute necessity for such rapid production will be evident when
it is known that no less than 110,000 feet, or about twenty miles length,
of such gutters were required--very nearly the distance from Buckingham
Palace to Windsor Castle.
Finished as described above, the Paxton's gutters arrived at the building,
where the first operation they underwent was that of cutting them to the
exact length requisite. This was a nice operation, as the smallest
deviation would have caused a difficulty in fitting them into their place,
and to perform it a framework was constructed by which the solid gutter
could be bent to the same curve it would have when fixed; a precaution that
was necessary in order that the ends might be cut off quite vertically so
as to fit together when in their place. At one end of this frame-work was
placed a circular saw, twenty inches diameter, hung with a pulley and
balance weight, so as to be moved up and down by means of a lever. The
gutter being fixed in the frame by means of hinged guage-plates, one end
was cut by the circular saw being brought down upon it; and at the same
time another operation was performed: two cutters, placed in the centre of
the circular saw, were so arranged that when brought down upon the end of
the solid gutter they cut out a semi-circular notch, so that when the ends
of two gutters were afterwards placed together there was a circular hole
left, through which the water passed down into the main gutter. When these
operations were completed at one end of the gutter, the guage-plates were
taken off, and the timber was swung round on a pivot or crutch in the
centre, and the same process gone through as before; the whole scarcely
occupying two minutes. We shall presently have to return to this piece of
machinery, as it was also used in finishing the ridge rafters.
[Illustration: MACHINE FOR FINISHING ENDS OF GUTTERS AND RIDGES.]
The solid gutter was now transferred to the hands of the carpenter, who
fixed at each end, on the under-side, a small cast-iron shoe; and two
struts, nine inches long, were placed so as to divide the whole length into
three equal parts--the struts spread out at the top in order to present a
large surface of pressure against the under-side of the gutter; and tenons
projected upwards, which were fitted into mortices cut into the timber. The
lower end of the struts were formed so as to give them a firm hold upon a
wrought-iron rod, thirteen-sixteenths of an inch diameter, which was passed
under them and through the shoes, where it was screwed up with nuts; and
the struts pressing up against the timber produced the requisite bend or
camber. Twenty-seven notches, to receive the sash bars, were marked with a
templet and cut out on each edge of the upper-side of the gutter; and a
small cast-iron plate having been fitted on the under-side at each end, the
Paxton's gutter was complete and ready for fixing. The under-trussing of
the rafters increased their strength considerably, so that a weight of
one-and-a-half tons was required to break one which was experimented upon.
The Sash-bars.
We will next consider the sash-bars which support the ridge of the roof and
receive the glass. The total length which was required of these amounts to
about two hundred miles; it will, therefore, be easily understood that
mechanical contrivance for cutting them out became an absolute necessity;
this Mr. Paxton appears to have discovered in his works at Chatsworth, as
he mentions in his lecture.
[Illustration: MACHINE FOR CUTTING OUT SASH-BARS.]
The sash-bars are one inch thick and one-and-a-half inches deep, and are
grooved on each side, besides having all the four edges bevelled or
chamfered; all which was done in one passage through the machine. The plank
which was to form the sash-bars was passed in at one end of the machine,
between pressure-rollers; it then passed between cutters placed both above
and below it, which made about twelve hundred revolutions per minute, and
hollowed out the different grooves; and, lastly, it passed between circular
saws which divided it into separate sash-bars, after which they had only to
be cut into their proper lengths.[6] The exact length of each sash-bar when
finished is four feet one inch.
In this state the skylight bars were sent to the building, where they
underwent several finishing operations, necessary to make the ends fit down
into the notches prepared in the ridges and gutters. Thirty of the bars
were first placed together in a horizontal traversing-frame on a saw-table,
on each side of which circular saws were fixed at the distance of the
required length of the sash-bar; the frame was then moved forward against
the saws, so that both ends of the whole set of bars were cut off
simultaneously, and at the same time a cut was made at one end half-way
through the bar, in order to form the shoulder against the gutter. They
were then removed to another bench, where the end of the bar was bevelled
and the shoulder formed by means of a small instrument having a handle with
two projecting jaws fitting into the ends of the glass grooves of the bars;
between these there was a small blade which, being pressed down, cut out
the shoulder which had been sawn through in the other direction, and
another blade was placed at the proper angle to remove the bevelled piece
at the end of the bar.
[Illustration: THE SASH-BAR DRILLING-MACHINE.]
One more process made the sash-bars complete for fixing--this was the
drilling a hole at each end to nail them down on the gutter and ridge; and
this was also done by machinery, to insure all the holes being drilled at
the same angle. On one side of a horizontal bench were placed a set of
four-inch driving pulleys (_a a_), with as many horizontal drills
projecting towards the other side of the bench; a wooden traversing-plate
(_c_) opposite each drill, and working towards it, received one end of the
sash-bar, while the other rested in an inclined position against a wooden
rail (_b_) placed longitudinally above the pulleys, having as many sinkings
thereon as there were drills. The traversing-plate being then pushed
forward, the sash-bar was perforated by the drill; the plate was then drawn
back, and the same operation repeated with the other end of the bar, which
left it ready for fixing.
The action of the traversing-plate (_c_) is shown more distinctly in the
second engraving.[7] One out of every nine of the sash-bars of the roof is
stronger than the rest, to serve for fixing the ridge previous to glazing.
These extra-strong bars are two inches wide and one inch and a half deep,
and were formed by the same machinery already described, by an adjustment
of the different cutters and saws.
[Illustration: PORTION OF SASH-BAR DRILLING-MACHINE.]
The Ridges.
The total length of these required was about sixteen miles. They are cut
out of timber three inches square, in section, and are of the form shown in
the diagram, with a groove on each side to receive the glass. This was also
done by machinery which, with about five-horse power, turned out one
hundred lengths of twenty-four feet in a day of ten hours, allowing the
time for the necessary stoppages. After they had been delivered at the
building, these ridge-pieces were cut to the exact lengths by means of the
same apparatus used for the solid gutters which has already been described.
At each end of the ridge-piece two holes were also drilled to receive
dowells to connect it with the adjoining length. By no other than
mechanical means could the immense number of holes thus drilled have been
placed so exactly that those in the opposite ends of any two ridge-pieces
should correspond precisely.
[Illustration: SECTION OF RIDGE AND ORDINARY SASH-BAR.]
The different essential component parts of the roof having thus been
described, we propose to take the different members of the construction in
succession downwards.
The Glass.
But first it may be mentioned here that the glass used throughout the
building is sheet, on an average about one-sixteenth of an inch thick, and
weighing one pound per foot superficial. This gives an aggregate weight of
about four hundred tons for the whole of the work, the greater part of
which was supplied by Messrs. Chance and Co., of Birmingham. Each square is
forty-nine inches long and ten wide, the greatest length of sheet glass
that has ever been made in this country. The manufacture of this kind of
glass is of comparatively recent introduction into England, though
practised for some time on the Continent; and the rapid progress made by
the manufacturers alluded to must be in a great measure attributed to the
wise removal of the fiscal burden on the article, made by the late Sir
Robert Peel. That lamented statesman, with his usual foresight, doubtless
contemplated that great social benefits would follow from that enactment;
and it is, perhaps, not too much to say that, but for Sir Robert's
enlightened measure, this "huge pile of transparency" would never have been
reared.
The Box Gutters.
It has been mentioned that the triple gutters deliver the water into main
gutters running in the transverse direction of the building; these are
formed of wood, with a bottom piece, into which are grooved two upright
sides, they are firmly bolted down upon the upper flange of the
roof-girders, and where these are quite horizontal the fall in the gutter
is given by a false bottom laid to a slope. Of these gutters there is a
length of about five-and-a-half miles in the building, which, added to the
aggregate length of the Paxton's gutters, makes a total of about
twenty-five-and-a-half miles of gutter.
Roof Girders.
These are of cast-iron, where not more than twenty-four feet long, and the
rest of wrought-iron. The cast-iron ones are precisely the same in
appearance as those used for the galleries, but lighter in metal; a
separate description of them is not, therefore, necessary. The weight of
each of these girders is twelve cwt., and each was proved to nine tons
previously to being used; but it is calculated that the greatest weight
they may have to bear will not exceed five tons: the total number required
was about 470.