Page:An Encyclopædia of Cottage, Farm, and Villa Architecture and Furniture.djvu/1133

 ARCHITECTURAL FITNESS. 1109 ductor," says Mr. ilurray, " is altogether unique, and without its couritcrp-jrt in Europe, as far as I know. It is constructed on principles deduced by me not merely from electrical phenomena developed by artificial experiments, but from repeated and careful inspection of the effects of lightning. It consists of copper gas-piping in lengths of about ten feet, screwed into sockets. The conductor terminates at the summit, in a pyramidal form, inserted by a joint into the hollow pipe ; the lightning therefore finds a ready entrance, not only by the sharp point, but by the angles of the copper pyramid. The pipe immediately beneath this joint is perforated, so that the lightning may be diffused over both sui-faces, internal as well as external, and the facilities of escape to the earth will be further increased by the wet that penetrates the tube during the rain which falls during the storm. This lightning rod is secured from oxidation by ribands of zinc attached at specific distances, which operate on galvanic principles ; and the conductor, thus constructed, enters the earth at a slight angle, and terminates in a stone trough, which will be supplied with sufficient moisture by the pipe. Here it is split in two, and its ramifications pass over the edge of the tank into the subsoil. Perhaps this con- ductor is not only the cheapest but the best ever constructed. The first, because, from a hollow pipe being employed, the weight of the copper, and consequently the expense, is materially diminished ; and the second, because in these conditions all the principles of security are provided. Copper is the best conductor of lightning, and, as lightning does not penetrate a good conductor to any appreciable depth, an extensive and an ample con- ducting surface is provided, and facilities both for its reception and final transfer to the earth fully supplied. Add to these, last not least, in the train of securities, there is no interruption whatever, from beginning to end, in the channel by which it descends from its elevation. A conductor on these principles has also been attached to a private house in the vicinity of Huddersfield." 2191. The Construction ~of Fireplaces and Chimney-flues in dwelling-houses is still very imperfectly understood ; very little having been added to our stock of knowledge on this subject since Franklin's Letter, &c., was written in 1785 ; or Count Rumford's Essays, a few years afterwards. The principal requisites to insure the di'aught of a chimney appear to be, a considerable height in the flue, such a construction at the fire- place as will allow as small a quantity as possible of air which has not passed tlirough the fire to ascend the chimney, and a free supply of external air to the room in which the fire burns. This supply should be obtained directly from the exterior atmosphere, either by having the windows not to fit too tightly, by letting down the upper sash at the top, or by having a tube of several inches in diameter, from underneath the fire-grate to an under-ground drain of ample dimensions. Clavering, Chadley, and Hiort agree in recommending circular or oval flues, as being more suitable to the motion of the smoke, and being more easily cleaned, than square ones. They also agree in recommending a zigzag or bending direction for flues, as preventing the wind from blowing down the smoke by the resistance offered by the bends ; and, according to Chadley, even improving the draught, which, it appears to us, they can only do, by producing a greater quantity of heated material in the sides of the flue, in proportion to its direct vertical height, than can be done in a flue earned up straight. It may also be observed, that the smoke, in a perpendicular flue, ascends in a column composed as it were of straight lines, like water running along a straight brook ; whereas, in a circuitous or zigzag flue, it ascends in cursed lines, or curls, or what may be called eddies, like water in circuitous brooks. In the first case, it is evident that the wind, strikingr down on the smoke, when it escapes the top of the flue, would produce such a pulsation as would force it out into the room ; whereas, in the other case, the force of the stroke of the wind would have to counteract all the different eddies, before the pulsation could reach the fireplace. In general, by attending to these desiderata, those unsightly objects, chimney-pots, may be avoided ; and indeed, oixr opinion is, that every one who employs an Architect or builder ought to engage with him, under a heavy penalty in case of failure, to arrange his design and its execution in such a manner that no chimney-pots shall ever become requisite. Thick walls for containing the chimney-flues, and for keeping them warm ; placing these flues as much as possible in the interior walls ; having lofty and winding flues, circular or oval in their section ; and having a supply of air to every hearth, or the back part of every fireplace, from air drains of large capacity, seem to us to be the prin- cipal means of insuring bright fires and freedom from smoke. Such fireplaces as iIethley's and Silvester's are also eminently favourable for this end. Methley's fire- places, by having the breast or upper part beveled downwards towards the fire, not only greatly diminish the quantity of cold air which enters what is called the throat of the" chimney; but, this beveled space being of metal, must necessai-ily raise the temper- ature of such air as does enter. In short, we do not know of any form of fireplace so well calculated for preventing a chimney from smoking, unless indeed it be that ot Sylvester, fig. 1844, of which, however, we have only had a few weeks' experience ;