plumber, who will soon discover and remedy the defect. If the pressure at the burner is too great, check this by turning the tap at the meter, and if the number of lights varies considerably, it will be desirable to fix an automatic regulator, which will ensure an even pressure at the burner whatever it may be in the mains. There are many such regulators sold-good, bad, and indifferent -probably more of the latter than the former, but one of the good ones which may be named is Stott's, this having gained, amongst others, the prize medal at the recent Crystal Palace Exhibition, 1882-3.

A common objection to gas is that it makes a room unhealthy, and that it destroys our books and pictures. This is frequently so, but the same objection applies to any other illuminant yielding the same quantity of light, if proper ventilation is not provided. It is well known that people are ordinarily satisfied with less light from lamps or candles than they would be from gas. Let us suppose four wax candles in the drawing-room, and four fairly good gas burners in the library. The light from the four burners will be sixteen times that afforded by the four candles, and if we treat ourselves in the library to so much extra light we must be prepared to put up with the proportionate ill-effects necessarily resulting from its production.

Let me not for a moment be understood as saying that impure gas is not injurious to health, or even to book bindings and pictures. It is undoubtedly so, but the injury generally arises from excessive heat, caused by the large quantity of gas used and deficient ventilation.

As in heating, so in lighting, the inventions and patented improvements are innumerable, and as these are usually said to give more light with less gas than others, we may not unreasonably expect shortly to have light from burners so improved that they will require no gas at all.

The efficiency of gas lighting does, however, depend to a considerable extent upon the burner and other appliances used. The steatite and porcelain have taken the place of metal burners, and flat flames have superseded ratstail and round flames. A moderate-sized burner, moreover, will yield a better light than a number of smaller ones burning the same quantity of gas. For example, a burner consuming five cubic feet per hour will give more light than five similar burners, each consuming but one cubic foot, and an efficient pressure regulator will secure to the burner

its proper quantity of gas for ensuring under all conditions a good and steady light.

Globes and shades interfere materially with the radiation of light. It is thought by many that they render it softer and more equable, but this is questionable, and it is certain that they absorb and waste a large percentage of light, amounting in some cases to as much as 50 per cent.

About ten feet of atmospheric air is required to mix with one foot of gas to ensure perfect combustion. The quantity varies of course with the quality of the gas, hence the difficulty of constructing a lamp which shall be equally good under all circumstances. A deficient supply of oxygen means little heat, and a low degree of luminosity. A sufficient supply gives a maximum of both, and an excess produces the same amount of heat, but less light. The Bunsen burner illustrates the latter example. A large proportion of air is mixed with the gas previous to its ignition, and the result is a sickly blue flame, with a concentrated heat, equal to, but not greater than, the radiant heat given off by the pure white flame. In the one case it is concentrated, and in the other diffused by radiation in all directions, hence in cooking appliances the Bunsen burner is the most effective for boiling, and the white flame, from a proper burner, most desirable in an oven, as the products of combustion in this case are less offensive.

The introduction of the " Regenerative burner" marks a new era in gas lighting. Dr. F. Siemens, one of the earliest inventors, says:"Under the Regenerative system the products of combustion are continuously returned by a downward current to the interior of the burner itself, and there utilized to heat fresh gas and air prior to use. The result is that combustion is absolutely perfect." The Grimston, Clark, Wenham, and other so-called "Regenerative" lamps in many respects resemble Siemens', and the favour with which these have been received by the public tends to show that they possess advantages over the ordinary burners. The Siemens' Patent Gaslight Company say that by their system the consumption of each cubic foot of gas gives a light equal to at least 50 per cent more than the light afforded by the old burners, and some of the other inventors claim even more.

An erroneous opinion prevails in regard to the action of these lamps, and the cause of their increased efficiency. The statements of some of the patentees even have tended to foster the illusion, one declaring that the high results are obtained simply

by an ingenious application of the regenerative principle, whereby the gas and air are raised to a high temperature by the heat of the flame underneath. The fallacy lies in the idea that perfect combustion requires the aid of extraneous heat, as such is not the case,

B B-Semi-globular glass hinged,
G G-Reflector. HH, K K-Air holes.

CC-Lamp top. D D', E E'-Concentric tubes
R-Burner.

and the greater efficiency is undoubtedly due to the larger quantity of air which the heated chambers of the lamp cause to be mixed with the gas as it issues from the burner.

The judges of the International Gas Exhibition, 1882-3, stated that Grimston's burners gave a light equal to 483 candles, and

Clark's burner a light equal to 4'76 candles per cubic foot of gas, whilst the best Argands gave from 313 to 363 candles only. "The results," they remark in reference to Clark's, "obtained with this burner, in all the positions, are remarkably good, and we are disposed to consider it the best burner tested."

In most of these Regenerative lamps some difficuty is experienced in lighting them, as, until a draught is created, the flame will scarcely survive, owing to a deficiency of air.

Mr. Schulke attempts to remedy this in his lamp by forming a combustion chamber immediately above the burner, and a special flue therefrom communicating with the main chimney above.

Another advantage of these lamps is the facilities they afford for ventilating the rooms.

VENTILATION.-We now approach the most difficult branch of our subject-difficult on account of the varied circumstances and conditions under which it is required, yet simple when viewed in reference to fundamental principles. We cannot overrate the importance of ventilation, neither can we thoroughly comprehend its urgency until we know exactly what it means. Literally this is "fanning," but as commonly understood, it means substituting fresh air for foul air. Nature has provided a perfectly healthy atmosphere, but man pollutes it both by himself and the agents he employs to minister to his comforts. This is more especially consequent upon combustion, and life itself may be called combustion. We have already seen that in an ordinary fire oxygen is required to mix with the carbon of the fuel, after which we have carbonic acid gas and earthy matter in the form of ash. So in the human frame, the food is the fuel, and the body is the grate where the carbon is consumed. Heat is generated in this slow combustion stove, carbonic acid gas is given off, and in place of smoke we have an imperceptible, but not less impure, gaseous vapour emitted by perspiration as well as respiration. So also in the case of a lamp or a gas burner, oxygen is abstracted and poisonous gases take its place, which, with the other products of combustion, so vitiate the air as to render ventilation an absolute necessity.

The human frame is, however, something more than a combustion stove, and may not inaptly be described as a regenerative furnace. Some writer has remarked that "the moment we begin to live that moment we begin to die," and to sustain life we must have a continuous re-vivifying of the materials composing the frame itself, but the process produces emanations and exhalations

which are offensive in themselves and injurious to the system if again inhaled, and we have therefore not only deleterious gases but effete and invisible solid particles of organic matter-the result of decay and decomposition-to get rid of.

It is generally admitted that foul air is fatal to health. "Doctors differ" is an old adage, but in this they do not differ, and to the medical profession above all others the public are indebted for a persistent advocacy of fresh air. The difficulty lies not so much in satisfying people that impure air is hurtful as in convincing them of its presence. They cannot see it, and in most cases cannot even smell it, consequently they will not believe in its existence, and hence their apathy.

We can no more exist without air than fish can live without water, and just as they are poisoned by polluted water, so are we by impure air. The evil is in proportion to the degree of impurity. A little produces listlessness; still more, headaches, and possibly fainting; and in extreme cases, suffocation, as in the oftquoted case of the Black Hole at Calcutta.

Professor Hosking makes this very pertinent remark: "People who would revolt at the idea of drinking out of the same cup or glass with a stranger, or even with a guest, suffer no annoyance from, and feel no disgust at, inhaling what has already passed through the lungs of those who may be shut up in a room with them, however close the room may be."

Chemists tell us that pure air is composed of 21 parts of oxygen and 79 parts of nitrogen, and that any alteration of these proportions implies deterioration. If, therefore, we take away a certain proportion of oxygen, and more especially if we substitute some other compound, such as carbonic acid gas, we necessarily destroy its health preservative properties. In that state it is a foe to health, we cannot cope with it at close quarters, and we are forced either to escape from it or compel its escape from us.

Ventilation implies movement-a current of foul air passing out, and an equal current of fresh air coming in. We, therefore, require an outlet and an inlet, and these should, as far as possible, be independent of both doors and windows. Under ordinary circumstances we find the temperature near the ceiling many degrees higher than at the floor level. Respiration, radiation from the fire and the gas lights primarily warm the lower stratum of air, but as this becomes heated it rises, and colder air from the immediate locality takes its place in like manner to be heated and