And the enriched coal gas would, therefore, cost 1s. 3/4d. per thousand, the extra 11/2-candle power having been gained at an expense of 3/4d. or 1/2d. per candle.

Tabulating these results we have - Cost of enriching a 16-candle gas up to 17.5 candle power per 1,000 cubic feet by cannel coal, 4d.; by Maxim-Clarke process, 2-6/10d.; by Lowe or Springer water gas, 11/2d.; by Van Steenbergh water gas, 3/4d.

In reviewing this important subject, and bringing a wide range of experimental work to bear upon it, I have, as far as is possible, divested my mind of bias toward any particular process, and I can honestly claim that the fact of the Van Steenbergh process showing such great superiority is due to the force of carefully obtained experimental figures, corroborated by an experienced and widely known gas chemist, and by the chief gas examiner of the city.

In adopting any new method, the mind of the gas manager must to a great extent be influenced by the circumstances of the times, and the enormous importance of the labor question is a main factor at the present moment; with masters and men living in a strained condition which may at any moment break into open warfare, the adoption of such water gas processes would relieve the manager of a burden which is growing almost too heavy to be borne.

Combining, as such processes do, the maximum rate of production with the minimum amount of labor, they practically solve the labor question. Requiring only one-tenth the number of retort house hands that are at present employed, the carbureted water gas can be used for enrichment until troubles arise, and then the gas can be used pure and simple, with a hardly perceptible increase in expense, while the rapidity of make will also give the gas manager an important ally in the hour of fog, or in case of any other unexpected strain on his resources.

One of the first questions asked by the practical gas maker will be: "What guarantee can you give that as soon as we have erected plant, and got used to the new process of manufacture, a sudden rise in the price of oil will not take place, and leave us in worse plight than we were before?" and the only answer to this is that, as far as it is possible to judge anything, this event is not likely to take place in our time. A year ago the prospects of the oil trade looked black, as the output of American oil was in the hands of a powerful ring, who seemed likely also to obtain control of the Russian supplies; but, fortunately, this was averted, and, at the present moment, the Russian pipe lines are flooding the market with an abundant supply, which those best able to judge tell us is practically inexhaustible, so that prices may be expected to have a downward rather than an upward tendency. But even should a huge monopoly be created, I think I have found a source of light at home which will hold its own against any foreign illuminant in the market.

For a long time I have felt that in this country we had sources of light and power which only needed development, and the discovery of the right way to use them, in order to give an entirely new complexion to the question of carbureting; and now by the aid of the engineering skill and technical knowledge of Mr. Staveley, of Baghill, near Pontefract, I think it is found.

At three or four of the Scotch iron works the Furnace Gases Co. are paying a yearly rental for the right of collecting the smoke and gases from the blast furnaces. These are passed through several miles of wrought iron tubing, diminishing in size from 6 feet down to about 18 inches; and as the gases cool, so there is deposited a considerable yield of oil.

At Messrs. Dixon's, at Glasgow, which is the smallest of these installations, they pump and collect about 60,000,000 cubic feet of furnace gas per day; and recover, on an average, 25,000 gallons of furnace oils per week, using the residual gases, consisting chiefly of carbon monoxide, as fuel for distilling and other purposes, while a considerable yield of sulphate of ammonia is also obtained. In the same way a small percentage of the coke ovens are fitted with condensing gear, and produce a considerable yield of oil, for which, however, there is a very limited market, the chief use being for lucigen and other lamps of the same description, and for pickling timber for railway sleepers, etc.; the result being that, four years ago, it could be obtained in any quantity at 1/2d. per gallon, while since that it has been as high as 21/2d. a gallon, but is now about 2d., and shows a falling tendency. Make a market for this product, and the supply will be practically unlimited, as every blast furnace and coke oven in the kingdom will put up plant for the recovery of the oil, and as with the limited plant now at work it would be perfectly easy to obtain 4,000,000 or 5,000,000 gallons per annum, an extension of the recovery process would mean a supply sufficiently large to meet all demands.

Many gas managers have, from time to time, tried if they could not use some of their creosote for gas producing, but on heating it in retorts, etc., they have found the result has generally been a copious deposit of carbon, and a gas which has possessed little or no illuminating value. Now, the furnace and coke oven oils are in composition somewhat akin to the creosote oil, so that at first sight it does not seem a hopeful field for search after a good carbureter, but the furnace oils have several points in which they differ from the coal tar products. In the first place, they contain a certain percentage of paraffin oil, and in the next, do not contain much naphthalene, in which the coal tar oil is especially rich, and which would be a distinct drawback to their use.

The furnace oil as condensed contains about 30 to 50 per cent. of water, and in any case this has to be removed by distilling; and Mr. Staveley has patented a process by which the distillation is continued after the water has gone off, and by condensing in a fractionating column of special construction, he is able to remove all the paraffin oil, a considerable quantity of cresol, a small quantity of phenol, and about 10 per cent. of pyridine bases, leaving the remainder of the oil in a better condition, and more valuable for pickling timber, which is its chief use.

If the mixed oil so obtained, which we may call "phenoloid oil," is cracked by itself, no very striking result is obtained, the 40 percent. of paraffin present cracking in the usual way, and yielding a certain amount of illuminants, but if this oil be cracked in the presence of carbon, and be made to pass over and through a body of carbon heated to a dull red heat, then it is converted largely into benzene, the most valuable of the illuminants, and also being the one to which coal gas owes the largest proportion of its illuminating power, it is manifestly the right one to use in order to enrich it.

On cracking the phenoloid oil, the paraffins yield ethane, propane, and marsh gas, etc., in the usual way, while the phenol interacts with the carbon to form benzene -

Phenol.		Benzene.
CHHO + C	=	CH + CO.

And in the same way the cresol first breaks down to toluene in the presence of the carbon, and this in turn is broken down by the heat to benzene.

A great advantage of this oil is that the flashing point is 110, and so is well above the limit, thus doing away with the dangers and troubles inseparable from the storage of light naphtha in bulk.

In using this oil as an enricher, it must be cracked in the presence of carbon, and it is of the greatest importance that the temperature should not be too high, as the benzene is easily broken down to simpler hydrocarbons of far lower illuminating value. This fact is very clearly brought out by a series of experiments I have made, in which the phenoloid oil was cracked by passing it through an iron tube packed with coke and heated to various temperatures, the hydrocarbons being much more easily broken up under these conditions than if mixed with diluents, such as water gas:

RESULTS OBTAINED ON CRACKING PHENOLOID OIL.
	I.	II.	III.
Temperature.	600° C.	800° C.	1,000° C.
Volume of gas per gallon.	41.6 c.f.	76.8 c.f.	121.6 c.f.
COMPOSITION OF THE GAS.
Hydrogen.	34.0	36.0	37.0
Methane.	20.0	26.0	49.0
Olefines.	11.0	5.0	Nil.
Ethane.	16.0	9.0	Nil.
Carbon monoxide.	13.0	15.0	12.0
Carbon dioxide.	2.0	4.0	2.0
Oxygen.	2.0	1.0	Nil.
Nitrogen.	2.0	4.0	Nil.

This analysis shows that if the temperature is allowed to reach a cherry red, complete decomposition of the illuminating hydrocarbons is taking place, and a gas of practically no illuminating value results. The power of regulating the temperature and the body of carbon as a cracking medium in the Van Steenbergh water gas plant especially fits it for using this oil, and removes the objections which could have been urged against the lighter naphthas.

This oil is at present not in the market, but given a demand, it can be produced in four months, at the latest, in very large quantities, as the apparatus is very easy and cheap to erect, and the crude material can be plentifully obtained.

If this oil becomes, as I think it will, an important factor in the illumination of the future, it will mark as important an era in the history of our industries as any which the century has seen, as, by using it, you are giving smoke a commercial value, and this will do what the Society of Arts and the County Council have failed in - that is, to give us an improved atmosphere. If I were lecturing on an imaginary "Hygeia," I should point out that the smoke of London contains large quantities of these oils, and they, by coating the drops of mist on which they condense, give the fog that haunts our streets that peculiar richness which is so irritating and injurious to the system, and, further, by preventing the water from being again easily taken up by the air, prolong the duration of the fog. Make this oil a marketable commodity, and another twenty years will see London without a chimney; underground shafts will be run alongside the sewers; into these shafts by means of a down draught all the products of combustion from our fires will be sucked by local pumping stations, and the oil condensing in the tubes will serve in turn to illuminate our streets, instead of performing its former function of turning day into night and ruining our health; but as I am not at all sure of the engineering possibilities of such a scheme, I will leave its discovery to some other abler prophet than myself.

(To be continued.)

[1] Lectures recently delivered before the Society of Arts, London. From the Journal of the Society.