274 THE BUILDING NEWS. Apri 5, 1872. GQWQ5uu350ewaeeeeSe of Fig. 66, especially where the roof is much exposed. For roofs without boards, No. 15 or 16 zinc ought to be used. The style of roll at Fig. 63, and the over- lap at T, Fig. 66, are something similar to the manner in which lead is put on for flats, &c., in many parts of Englard and Ireland, but neither can for a moment compare to the style of roll shown by Fig. 27, p. 199. I would, therefore, respectfully recommend the style of laying lead on'flats described at p. 199 as being much better than the styles where wood is used for rolls, The gutters for these zinc-coyered roofs may be of many patterns similar to those we have already described ; and, in addition, we have the zinc eave-gutter (Fig. 68) which may contain various enrichments in stamped zinc ; the boundary-wall gutter (Fig. 69); the plain “‘box-gutter” (Fig. 70),or the same with sloping sides, as per Fig. 71, for centre-gutter on double roofs. Fig. 72 is the common style of centre-gutter on double roofs in south-west of Scotland. In using zine for roofs there are two situations in which it does not stand so well—viz., quite close to the sea- side and where it is much exposed to the fumes from chemical works; but these are ex- ceptional situations. In the article on “ Zinc” in Gwilt’s “ En- cyclopdia of Architecture,” we are told that zinc is much more used in France than in England, and it goes on to say :—‘‘ Zinc, though subject to oxidize, has this peculiarity, that the oxide does not scale off as that of iron, but forms a permanent coating in the metal, impervious to the action of the atmosphere, and rendering the use of paint wholly unnecessary. Its expansion and con- traction is greater than those of any other metal; thus, supposing 1:0030 to represent the expansion of it, 1:0019 is that of copper, and 1-0028 that of lead; hence, in use, proper attention must be paid to this circumstance, or a substantial and durable covering of zinc will not be obtained. The method of accomplishing this is, of course, by always allowing plenty of play in the laps. The tenacity of zinc to lead is as 16-616 to 3°328, and to copper as 16:616 to 22-570; hence a given substance of zine is equal to five times the same substance in lead, and about three-fourths of copper.” The gauges of zinc recommended for roof- ing purposes are Nos. 13, 14, 15, and 16. The following table of a number of the various gauges, and their corresponding weights, may be useful. The weights given are not absolutely correct, there being slight variations in the weight of sheets of the same gauge, some being a little heavier than as given in the table, others a little lighter :— Sheet-zinc Weight per Weight of sheet gauge. sq. foot. 8ft. by 3ft. No. oz. dr. Ib. 8 ene 9 0 0 13} 9 = 10 13 . 164 10 % 125 5 183 ul ce 15 0 4 224 12 see 17 0 te 253 18 ove 19 5 ' 29 14 Be 21 12 82¢ 16 one 24 0 36 16 oo 26 0 39 Parties wishing further information about the use of zine for roofing purposes, in con- nection with the walls and timbers, &c. (as zine is lighter than slates thinner walls and slighter roofs may often serve) may obtain it from the architects specially retained by the Vieille Montagne Zinc Co.—viz., James Edmeston, Esq., 5, Crown-court, Old Broad- street, City ; or Messrs. J. and R. Fisher, 17, Great George-street, Westminster. I may here say a few words about drips for gutters, and in the first place I have to thank the various gentlemen who have taken part in the correspondence which has taken place in the pages of the Buitp1nc News upon the subject, and trust they will, as opportunity occurs, continue to favour us with their re- marks. At page 171, 3in. drips were re- commended, the reason being that where that depth is given capillary attraction is
prevented by cutting off the upper lead lin. from sole of lower gutter, as per U, Fig. 73. In doing so 2in. of perpendicular overlap is left, which is quite sufficient, and better than if it were 3in., and so made to come into contact with sole of lower gutter. When the depth of drip is so little as only lin. or 1}in., then the upper lead is brought over the lower, as per Fig. 74, or, still worse, as per Fig. 75; the workman thinking that the half-inch margin at V, Fig. 75, is an improvement upon Fig. 74, and also makes a capital job, whereas it only shows his own ignorance of the principles which should govern his work. Instead of guarding against capillary attraction, the style of drips at Figs. 74 and 75 actually encourages it, more especially the latter. The lead which goes up sides of lower gutter at drips should be turned in, or doubled over a little, so as to form a small roll, the line of said roll being keptinside line of drip ; this tends to prevent any water coming down roof getting in side- ways over drip. The sides of upper gutter at drips should be left projecting out before drip about 3in. or thereby. The depth of drips on lead or zine-covered flats should be from about din. to 5in., according to size of rolls; those at Z Z, Fig. 41, with 2in. roll- caps should be about 44in. deep. With 1Jin. roll-caps, as per Fig. 50, drips 4in. deep would do, and less for Fig. 63. In answer to the question—W hat should be done if zine- covered flat, such as is described at page 212, were 23ft. broad instead of 15ft.? I may say that in sucha case about 4ft. should simply be added, on each side of centre-block, to tops of sheets, the first sheets extending from edges of flat W W, Fig. 76, up 7ft. 9in. to X X, and the two 4ft. pieces extending from X X to centre-block Y. There being an overlap of lin. at X X, which overlap has to be soldered all the way across sheet and and up upstand, thus, if I may so speak, transforming the 8ft. sheets of flat at page 212 into sheets 12ft. long; and still keeping each sheet by itself, and not attaching it in any way to the others on its right or left. « (To be continued.) — THE CAUSES AND PREVENTION OF FIRES.* IRE originates either spontaneously or by direct communication of flame or a strongly heated body to combustible substances. Spontaneous in- flammation is usually caused by the action of air on vegetable or animal oil exposed on fibrous, woven, or other highly porous material. Coals, also, which contain much sulphur, if stored in large quantities when damp, or if the heaps become damp, not un- frequently catch fire without external application of flame. Finally, fire has been developed by the friction of machinery. These are the only important forms of spontaneous combustion. This variety of fire occurs the more readily the higher the tempera- ture ; hence it occurs more frequently in summer than in winter, and in the vicinity of heated pipes and stoves than in cooler places. Fires caused by direct communication of flame or highly-heated matter originate—(1) in a manner which cannot well be foreseen or expected; (2) by the thoughtlessness or want of intelligence of uneducated or even educated persons; (3) by carelessness; (4) wilfulness. 1. Under the first head come fires starting from a beam running into a chimney, from floor-joists carried under the hearth of a fireplace, from boards under gas-stoves, and other stoves placed on wood floors without intervening layers of air and metal, and from wood wedges or shelf supports driven into the shallow brickwork of flues; also fires started by flame momentarily in contact with wooden beams, shelves, or boards which have become highly inflam- mable through being desiccated by constant proxi- mity of large gas chandeliers ‘‘ sun-burners,”’ heated flues, &c, These fires—and those caused by pro- longed contact of over-heated stoves, flues, and ovens, with adjacent woodwork—occur more especially in factories, bakehouses, churches, chapels, theatres, and other public buildings. Fires originat- ing in the ignorance of persons respecting the ready inflammability of mineral oils have been treated of in
- From a letter by Jo“n ATTFIeLD, Professor of Practical
Chemistry to the Pharmaceutical Society, London. Analyst to the Fire Insurance Offices. Inthe Times of April 3, 1872.
one of my former letters to the Times. 2. Fires
which originate through a lack of intelligent
forethought are of the following character :—
Roof fires, where wood, thatch, or tarred felt are so
arranged that sparks from a chimney are likely
to fall on and ignite these materials ; clothes fires,
where clothes-horses are so insecurely placed before a
grate that a slight touch or puff of wind causes
them to fall on the burning coals; fires caused by
candles or lamps being placed where they are likely
to be upset, or jointed gas-brackets so hung that
they are liable to be pushed beneath a wood shelf,
against curtains or other drapery, or among ribands
and such goods in a shop window; fires in farm
buildings and ricks originating from sparks blown
out of the furnace funnel of a portable steam-en-
gine; lastly, fires caused by lightning, where the
owner has neglected to protect buildings by a con-
ductor. 3. To actual heedlessness is to be traced
avast number of fires. he careless use of matches
in England alone is said to result in the loss of
£30,000 worth of property annually. They are
dropped about unlighted, and subsequently ignited
by friction of the boot of a person walking over
them ; after use they are thrown away in a glowing
or even a flaming condition, and falling among com-
bustible materials smoulder and presently cause a
conflagration ; children are allowed to gain access to
them; servants, after raking the kitchen grate at
night, place them on hobs to dry, probably with
several bundles of firewood, even after being warned
that the heat remaining in the stove may be suffi-
cient to cause such things to catch fire after some
little time. Prairie fires, and the grass fires and
stubble fires which occur on farms in England dur-
ing a hot summer, have been known to originate in
the careless use of matches end fusees by smokers.
Similar consequences have been traced to a sports-
man allowing a gun-wad to smoulder on the turf.
Plumbers and other workmen who have occasion to
use braziers or portable furnaces often exhibit great -
want of care in placing their apparatus where
sparks, red-hot cinders, or heated irons may ignite
woodwork. 4. Deliberate incendiarism has been
practised for the sake of the petty rewards given to
those who first call the engines to a fire; sometimes
also maliciously; but the desire to hide theft or
forestall bankruptcy or fraudulently to obtain money
from insurance offices is the commoner motive.
Fire extends from article to article in an apart-
ment, from room to room in ahouse, from house to
house in a block of buildings or warehouses, and from
block to block across streets and open spaces, by
tongues of flame, by the glowing fragments of
burning materials carried by currents of air, or by
the heat radiated from a mass of burning matter. The
rapidity with which fire extends among goodsin a
chamber of a warehouse is often greatly increased by
an injudicious classification and storage of the con-
tents. I haye seen jute and other fibres, as well as
boneblack and other porous materials stored beneath
casks of oil; oil stored where, should it catch
light, it would flow under doorways from one floor
to another, or on the surface of water among
shipping, igniting all combustible articles on its
way; spirituous liquids stored in warm _ places;
sulphur packed next to nitre and chlorate of petas-
sium; and, in short, goods of all kinds stored in
ships, railway trains, and warehouses without the
slightest discrimination as regards their relation to
fire. The extension of fire from room to room in @
private house ismuch facilitated by the wooden or
semi-wooden partitions which separate one room from
another, by the combustible character of floors,
staircases, and roofs, and by long jets of gas
escaping froma melted or broken gas-pipe. The
risk of extension of fire from house to house in a
row or terrace, or from one chamber to another in
warehouses, is considerably augmented by beams,
girders, rafters, and other timbers being carried
through without break from one house or wareroom
to another.
With regard to the prevention of fires, the tables
of trite suggestions for avoiding fires which have
been published from time to time are long, yet in-
complete, but would be useful if they could be found
when wanted or fixed on the memory. Instead of
offering such a list of precautions against fire, the
writer of this letter would now endeavour to bring
before your readers the really considerable experience
respecting fire and its properties which every grown
person possesses, methodically arrange such infor-
mation, and then leave its owner to apply his know-
ledge at the proper time with whatever amount of
skill, courage, and presence of mind he may be able
to command.
After what has been stated concerning fires which
arise spontaneously, it will be obvious that manu-
facturers, warehousemen, supercargoes of ships,
goods managers of railways,and others cannot with im—
