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refers to the smoke (a) more particularly—that is the carbon, or soot.

Anticipating, we may assume that the danger arising from the carbonic acid gas will be greatly reduced by the diffusion of gases, and if a nuisance injurious to health arising from the combustion of coal in the form of carbonic acid gas (although the smoke was consumed) was proved to exist, proceedings might be taken under the head of an offensive trade.

A nuisance of this description will be rare, being prevented by the beautiful law of the diffusion of gases just referred to.

Returning, then, to the process of the combustion of coal, we find that an insufficient supply of air causes the carbon to pass into the chimney in the form of soot or smoke, whereas with a sufficient supply of air it forms carbonic acid gas.

Whether carbon as smoke, or carbonic acid gas, is the most injurious to health, is a question for abler men than myself to decide. It is, however, apparent that we must accept one or the other, or portions of each.

Our duty under the Act appears to be to have the smoke prevented. It is, therefore, of the utmost importance for the inspector to become acquainted with the principles of smoke preventing, so that he may (although not specially called upon by the Act so to do) give information to tradesmen who are anxious to carry out the requirements of the law, but who are

(a) As to smoke nuisance in the metropolis, see section 19 of Sanitary Act, 1866.

gases to

pass up the

often wandering about among the many patents like a child in a fog, not knowing which to adopt.

When speaking of smoke consuming, we must bear in mind that it is really smoke preventing that requires our attention. That smoke can be prevented there is no denying the fact. In carrying this into effect there are two objects to attain :--1st, to regulate the supply of oxygen to the requirements of the combustion going on inside the furnace, bearing in mind that too little allows the carbon to go up the chimney in the form of soot and smoke, and that too much oxygen reduces the temperature so low as to cause the chimney without becoming ignited, and thus causing smoke; 2nd, to make provision by which the gases may be subjected to a high temperature, and for such a length of time as to ensure their ignition, and thus cause the carbon to become carbonic acid gas instead of assuming the form of smoke.

As to the best methods of preventing smoke, we must first take into account the supply of oxygen, which is a most essential feature. For every 100 lbs. of coal there should be passed into the furnace 178 lbs. of oxygen, which will of course require 740 lbs. of atmospheric air. The mode of supplying this oxygen is also a matter of importance, inasmuch as to have fixed openings in the door for the admission of air in sufficient quantities would be a great waste of fuel, as the cold air would, after the smoke was consumed, reduce the heating power without attaining any object essential. For the purpose of obviating this waste of heating power several patents have been brought out. For the purpose of explanation, I will make reference to the one known as “Broadbent's Self-acting Smoke Preventer and Fuel Economiser,” which is an automatic apparatus fixed to the boiler front, by which certain openings are opened and shut as the oxygen is required, which is done by the opening and shutting of louvres.

One of the peculiarities of these louvres is in the arrangements of the laths, which are so mounted upon their pivots that upon being drawn back to their full extent, which takes place upon the closing of the doors, they only admit one-half the quantity of air of which they are capable, but upon the gradual falling of the weight the louvres open to their full extent.

A continuation of the same motion, however, eventually closes them, in which position they remain until the door is again opened.

The admission of air in the above proportions coincides, as nearly as possible, with the requirements of perfect combustion. It is much more effectual, and certainly more economical, than the usual plan of admitting the full quantity on first charging the furnace, when it is not required, and having a deficient supply when it is most needed.

There is, however, another object to be gained in conjunction with the preceding one: that is, as before stated, to subject the gases evolved during combustion to a high temperature, and for such a time as to ensure their ignition, without which, it must be remembered, the gases go up the chimney in the form of smoke. I may here remark that if the reader will observe for himself, he will generally find those chimneys smoke most where the furnace and chimney are close to each

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other, without any length of flue, which is accounted for in this way, that so soon as the gases are evolved from the coal they are hurried up the chimney, whereas. in a large or long flue the gases have to travel for some time through what might be termed a hot oven, thus subjecting the gases to a high temperature for a considerable time, and thereby ensuring their ignition.

Where it is found the flue is too small or too short, a hot air chamber, or oven, should be constructed between the furnace and the chimney, with its inlet and outlet so arranged as to detain the gases for a short time in their passage to the chimney.

If the principles here recommended are properly carried out, I am confident that the smoke will be so far prevented that no nuisance will arise, and that no legal proceedings could be sustained against the owner of a furnace.

Out of London the sanitary inspector gives notice to abate smoke nuisances under section 91 of the Public Health Act, 1875.

CHAPTER VII.

DETECTION OF DISEASED MEAT (a).

THE detection of diseased and unsound meat and food is one of the most important and sometimes difficult duties that the inspector is called upon to perform. He must, therefore, make minute and close observations in all cases which come before him in his earlier experience, so that, with a little practice, he will have full confidence in himself when called upon to give his. decision, which will often occur in large towns.

Decomposed meat or food will come under the term unsound or unwholesome, and may generally be detected by the smell. The inspector in these cases will be guided by the stage of decomposition at which the article has arrived, and is recommended not to attempt to draw the line too fine, unless supported by the opinion of the medical officer.

With diseased meat the case is somewhat different ; if he is in a position to prove that the carcase is that of a diseased animal the case may be considered clear, inasmuch as the section of the Act, 117, c. 55, is definite upon the point as to diseased meat being condemned. I may, however, remark that at the hearing

(a) Seizure of meat in the metropolis : see section 2, Nuisance Removal Act Amendment Act, 1863.

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