fresh-air entrance channel, thus supplying a larger heating area for the entering air. The terra-cotta stoves in Herbert Hospital are of this description.

A very cheap and improved fresh-air cottage grate has been devised by Mr. Penfold of London. It is composed of well burnt fire-clay, with a chamber at the back, as in Galton's stove, in which the fresh air can be heated and discharged into adjoining rooms. This plan of supplying adjoining rooms with heated air was first introduced by Cardinal Polignac in 1713.

In order to secure the combustion of the smoke, several grates have been invented. One of the most recent, and which has been well spoken of, is that patented by Messrs. Young Brothers of Cheapside. The coals are introduced into a trough fixed to the lower portion of the front of the grate, then, by means of a right and left handed screw worked by a ratchetwheel, the burning fuel is raised, and the contents of the trough emptied into the cavity.

Of the numerous stoves intended to economise fuel, it will be sufficient to notice only a few of those which have been found to work more or less successfully as ventilating stoves.

1. The Goldsworthy-Gurney Stove. This consists of a plain iron cylinder, surrounded by a series of upright gills or flanges, and placed in a water pan, in order that the heat rendered latent by evaporation may be carried to the distant parts of the room in the moistened currents of air which proceed in all directions from the stove. The fresh air enters through a channel opening beneath the stove, and is heated by the warm flanges surrounding it. As the water in the pan is steadily

evaporated by the heat of the stove, the air in the room never becomes burnt or over-dried.

2. Musgrave's Slow Combustion Stove.-This resembles the Gurney stove in being surrounded by rows of flanges or ribs, but is more complicated in its internal arrangements. The receptacle for the fuel is lined with fire-clay blocks, and is large enough to contain the fuel necessary for twenty-four hours' consumption. As the fire is lighted from beneath, and the stove is charged through a sliding-door at the top, the fire may be kept burning for a whole year without requiring re-lighting, provided it be regularly fed and the ashes not allowed to accumulate. Before escaping through the smoke-flue the smoke and other products of combustion are forced through two auxiliary spaces in the stove, and impart almost the whole of their heat to the stove with its appendages during their passage. The fresh air to be heated is supplied by a special channel.

3. Pierce's Pyro-pneumatic Stove-Grate. In this stove the fuel is burned in an open grate, surrounded by fire-lumps, which impart their heat to the fresh air entering beneath.

4. The Calorigen Stove, lately invented by Mr. George, is adapted for burning gas, or as an open fireplace. The body of the stove is made of thin rolled iron, and contains a coil of wrought-iron tubing, which is open at the top of the stove, and communicates with the external air beneath. The fresh air is warmed during its passage through the coil, and enters the room at a moderate temperature. Connected with the gas stove is a cylinder placed outside the wall, and furnished with two pipes which communicate with the interior of the stove.

This cylinder is open at the top, and admits

the air necessary for the combustion of the gas, which is warmed to a certain extent by the products of combustion passing along the upper horizontal tube and issuing through the same opening (see fig. 5). Waste of heat is thus prevented, and any communication between the furnace of the stove and the air of the room is avoided. In the other stove the air of the room supplies the fire (see fig. 6). According to Mr. Eassie, C.E., 14 lbs. of coal burned in this stove will suffice to heat a room of 15 feet square for 16 hours. There is no doubt, therefore, that the Calorigen is economical, and as it affords equable warmth with good ventilation, it has been highly commended.

A-the interior of the room; B-exterior of the Building; C-Wall; D-the Calorigen; E-a Cylinder; F-Pipes communicating to supply air for combustion, and carry off product; G-Pipe for passage of Cold Air to Calorigen; H-outlet for ditto after being made warm; I-Gas-burner; J-Door.

The great objection to many of the commoner kinds of stoves depends on the fact that their over-heated surfaces dry the air to a very unwholesome extent, even

when the fresh air is conveyed by a special entrance channel. Numbers of them, however, are put up without providing any such channel, so that the air not only becomes dry and burnt, but exceedingly close and unpleasant. Evaporating dishes placed on the stoves will assist in remedying this evil, but it is much preferable, and in the long run more economical, to have a good ventilating stove erected in the first instance.

For all ventilating stoves it is necessary that the fresh-air channels should be removed from all sources of contamination, such as drains, closets, stables, etc. And it is advisable to protect the external openings by perforated bricks or gratings. The size of the stove, and the sectional area of the air-channel, must of course be regulated by the size of the space which is to be warmed and ventilated.

Stove smoke-flues may be either ascending or descending, but in the latter case a pilot-stove or rarefier ought to be fixed at the base of the upright chimney which receives the flue, otherwise the draught may prove Soot doors should be provided at all the bends, wherever practicable.

faulty.

With the ordinary grate, the ventilation of a room may be very greatly improved by providing an entrance into the chimney near the ceiling, and to prevent reflux of smoke, the opening should be valved, as in Dr. Arnott's chimney ventilator. One or more openings for the entrance of fresh air could be obtained by inserting perforated bricks or Sheringham valves in the outer walls, also near the ceiling, but at a distance from the fireplace.

Instead of an opening leading directly into the chimney for an outlet, a much better plan is to have a flue

running alongside the chimney, the entrance to the flue being situated near the ceiling. The hot air in the chimney warms the flue, and there is thus a constant upward current established without any risk of reflux of smoke. But this is an arrangement which can only be attended to in the original plan of a building; it cannot be applied as an improvement afterwards.

Some architects recommend that all the rooms in a well-constructed house should be supplied with warm air from the hall and staircase. In Mr. Ritchie's plan the air is heated to about 70° Fahr., and enters the various rooms through longitudinal openings over each door. After being diffused through the rooms it then passes up the chimneys and through flues reaching from the ceiling to the wall-heads under the roof.

Large and compact buildings, such as hospitals, asylums, and prisons, can be very efficiently warmed and ventilated by a suitable arrangement of hot-water pipes. The fresh air, as it enters through openings properly distributed throughout the building, is warmed by passing over the pipes, while the vitiated air may be extracted by means of other coils of heated pipes situated in extraction-shafts.

Another mode of ventilation by extraction, and one which is frequently used in prisons, consists in having a large foul-air extraction shaft or shafts, heated by a furnace at the bottom, and into which foul-air flues, leading from all parts of the building, are conducted. The workmanship in this case requires to be very perfect, so as to prevent any large currents of air reaching the shaft except through the flues.

By a combination of these two methods-viz. heating the fresh air before entering by hot-water pipes,