The temperature is lowered, fresh air appears, and oxygen is rapidly taken up by the finely divided iron, each particle heating so rapidly as to give a red heat to the mass. As carbon is able to overcome quite strong chemical affinities, and will reduce the oxide under strong heat, theoretically it is possible, and the authorities all tend to prove it. Considering all the points bearing upon hot water and steam pipes, also heating flues, an explanation is found of the great number of fires occurring at the approach of winter, and which are reported as from defective flues, supposed , incendiary origin, or causes unknown. Steam pipes packed in sawdust or shavings to retain the heat while steam is conveyed to a distance have given fires. One peculiar and important instance is on record of a fire from steam pipes. In the drying room of a woollen mill, a pine board was placed some 3-4 in. above the steam pipes to prevent wool from falling upon them. A fire followed, and after being put out, a careful examination determined to the satisfaction of all, that the heat of the pipes had distilled the pitch from several knots in the pine board, and this dropping on the pipes had ignited and caused the fire.

The illustration needs no comment, as the lesson is too plain to need pointing out. (Dr. Tanner.)

Fireproof. Whitewash. - It is found that a most effective composition for fireproofing exterior surfaces may be formed by slaking a sufficient quantity of freshly burned quicklime of the best grade, and when the slaking is complete there is added such an amount of skim-milk, or water in its absence, as will make a liquid of the consistency of cream. To every 10 gal. of this liquid are added, separately and in powder, stirring constantly, the following ingredients in the order named: 2 lb. alum, 24 oz. subcarbonate of potassium or commercial potash, and 1 lb. common salt. If white paint is desired, no further addition is made to the liquid, though the whiteness is found to be improved by a few oz. plaster of Paris. Lampblack has the effect of giving a number of shades from slate-colour to black. Whatever tint is used, it is incorporated at this stage, and the whole, after being strained through a sieve, is run through a paint-mill. When ready to apply, the paint is heated nearly to the boiling point of water, and is put on in its hot condition.

It is found that the addition of a quantity of fine white sand to this composition renders it a valuable covering for roofs and crumbling brick walls, which it serves to protect.

Fireproof Floors

At a meeting of the Society of Engineers, a paper was read on the above subject by G. M. Lawford. After alluding to the concrete floors and roofs of the Romans, the history of fireproof flooring was briefly traced, showing how the brick arch gradually gave way to the different applications of concrete and wrought iron now in general use. The objects of fireproof flooring were stated to be as follow: -

(a) To divide the building into a complete series of fire-resisting compartments.

(6) To gain strength, and in so doing to avoid lateral thrust on the walls, and to distribute the weight equally over them.

(c) To render the floors soundproof, as well as fireproof, and

(d) To secure the building from both dry rot and damp.

Detailed descriptions were then given of the following types of construction as instances of modern practice: -

(1) The concrete arch floor, illustrated by Dennett's and Wilkinson's systems.

(2) The flat, or suspended concrete floor, illustrated by Dawnay's, Lindsay's, and Gardner's systems.

(3) The arch block, or American floor, illustrated by the Doulton-Peto system.

' (4) The flat brick, or French floor, illustrated by Homan and Rodgers' system.

(5) The solid wooden floor, illustrated by Evans and Swain's system.

Several other systems were briefly described, as having been introduced from time to time with varying success, including those now in vogue in French and American practice.

After contrasting the individual floors, and the different types of construction, the two leading features for consideration were stated to be: -

(1) Which system gave most protection to the iron work supporting the floor?

(2) Which of the different materials employed gave most resistance to fire?

On the first question, the solid wooden floor (Evans and Swain's), requiring no iron work for spans up to 30 ft., was considered to be the best; but next to it, and certainly in advance of the others on this point, was placed the Doulton-Peto floor, the hard burnt clay blocks, with their overlapping bases, forming a most efficient protection to the joist. There was little to choose between the arched and flat concrete floors, as in the former there were comparatively few joists dependent on a plaster covering, while in the latter there were 4 to 6 times the number of joists, but completely encased in concrete; except in the case of Homan and Rodgers' floor, in which both T-irons and joists depended on a plaster covering. On the second question a comparison was made between concrete in the different forms employed, brick work, terra cotta, and solid wood, and it was stated that for fire-resisting* concrete, broken brick was preferable to coke breeze, as the action of intense heat tended to make burnt clay harder still, while coke breeze would calcine and burn away.

The flat brick and terra cotta floors were both open to the objection that the floors were constructed in layers of materials differently affected by heat; but the terra cotta floor, giving better protection to the iron work, was entitled to the preference, while the solid wooden floor, though inflammable by nature, would probably give as much resistance as either brick, concrete, or terra cotta floors. A floor of the flat brick type, designed and patented recently by William Lindsay, jun., deserved recognition, as apparently fulfilling the two requirements laid down by the author; but as it had not yet been used, criticism would be premature. It was, however, observed that the cost and weight were less than those of any of the similar floors in the appended table. The conclusion arrived at finally was, that although the floors described were capable of giving great resistance to fire, retarding its action by confinement, and in this way giving greater chances of extinction, a brick arch was the only absolutely "fireproof " floor, and that it would be more correct to describe the others as " fire resisting."

The houses of the fireproof towns of the River Plate are built as follows, the material being brick. Each floor, and the roof (which is flat), is supported by joists of hard wood, about the same distance apart as in this country; across these are laid flat rails of the same, and the spaces between these are bridged over by thin bricks 13 1/2 in. long, their ends resting on the rails;.

Table Giving Relative Cost, Weight, And Safe Load Of A Floor

Table giving Relative Cost, Weight, and Safe Load of a Floor, 12 ft. Bearing, in the Different Systems Described Above: -

Arch construction.

Cost rer sq. yd.

Weight per sq. ft

Exclusive of Joists.

Inclusive of joists.

Exclusive of Joists.

Inclusive of Joists.

Safe load per sq. ft.

Length of arch.

Span.

s.

d.

s.

d.

lb.

lb.

cwt.

ft.

ft.

Dennet

. 6

9 .

. 9

3

. 50 .

. 54 .

• 2

12

10

Doulton

. 0

6 ,

,. 9

0

. 30 .

. 34 .

. 2 .

12

6

Wilkinson .

. 6

0 ,

. 7

6

. 50 .

. 52 .

. 2 .

12

10

Flat construction.

Bearing ft.

Dawnay

• •

. 7

0

• • ' •

. 40 .

. 2 .

12

Immaterial.

Gardner

.

. 7

0

• • •

. 46 .

. 2 .

12

",,

Homan and Rodg

. 7

0

• • ^" - •

. 35 .

• 2 . •

12

,,

Lindsay

■ •

.

. 7

0

• • •

. 44 .

. 2 . •

12

,,

Evans and Swain

. 10s.

6d.*

. 20

lb.

. 7 .

12

,,

* No Joists required. (G. M. LAWFORD).

another layer of bricks is then laid with lime, and generally on this a layer of flat tiles. The roof is exactly the same, but has a slope of about 1 in 30. Then the doors and windows have no boxes, but simply frames, which are set up on building the walls, and built in. There is no lathing, nor wainscot, nor skirting of the bottom of the walls. And all the wood is of the hard and hardish kinds, slow to ignite Thus the houses are, as already said, absolutely fire-proof. (T. Gibson.)