of this modus operandi would be that fuel to be converted into gas is introthe illuminating gas supplied, say in duced through a hopper, and the cinder London, from Newcastle coal, would and ashes work out through the open probably exceed 20-candle power, instead orifice at the bottom. of 16, as at present, whereby the objectionable results of gas lighting would be greatly diminished, and there would be, say, an equal volume of heating gas available, consisting for the most part of marsh gas, which, although greatly inferior to olefiant gas in illuminating effect, would be actually more suitable for heating purposes, because less liable to produce soot in its combustion.

The total cost of production would not be increased by this separation of the gases, and the price might, with advantage both to the supplier and to the consumer, be so adjusted that the latter, while paying for his illuminating gas an increased price proportionate to the increase of illuminating power, would be furnished with a heating gas at greatly reduced cost; for the heating gas would be reduced in price in a much larger proportion than the illuminating gas would have to be raised, because it would not require the same purification from sulphur which renders illuminating gas comparatively costly. The enormous increase of consumption would moreover enable the gas companies to reduce prices all round very considerably without interfering with their comfortable reve

nues.

Instead of a grating for the introduction of atmospheric air a current of heated air is brought in, either through the hopper or through the orifice at the bottom, and is discharged into the center of the mass of fuel; the effect is the generation of a very intense heat at that point. The fuel, after its descent through the hopper, arrives gradually at this region of intense heat, and when subjected to it, parts with its gaseous constituents. At the point of maximum heat coke is consumed, producing carbonic anhydride, which, in passing through the considerable thickness of fuel surrounding this portion, takes up a second equivalent of carbon and becomes changed into carbonic oxide. Here also the earthy constituents are for the most part separated in a fused or semi-fused condition, and in descending gradually reach the orifice at the bottom, whence they are removed from time to time. Air enters through the bottom orifice to some extent, causing the entire consumption of the carbonaceous matter, which may have got past the zone of greatest heat; water is also here introduced in a hollow tray, and after evaporation by the heat of the hot clinkers, passes upwards through the incandescent mass, and is converted by decomposition into carbonic oxide and hydrogen gas. The exit orifices for the gases are placed all round, near the circumference of the chamber, ascending upwards into an annular space, whence they are taken through pipes to the furnace or other destination. The advantages connected with this modus operandi consists in the intensity of the heat produced within the center of the mass, whereby the whole of the fuel is converted into combustible gases, with the least amount of nitrogen. The hydrocarbons formed in the upper portion of the apparatus have to descend through the hotter fuel below, and in so doing, the tar and other vapors mixed up with them are decomposed, and furnish combustible gases of a permanent character.

For large applications of heating gas to the working of furnaces and boilers, simpler means than the retort can be found for its production. I constructed a gas producer many years ago in connection with my regenerative gas furnace, which I need not now describe in detail. In it all the carbonaceous matter of the coal is converted into combustible gas, the solid carbon yielding a supply of carbonic oxide; the resultant mixture of combustible gas contains a very large proportion, averaging 61.5 per cent., of nitrogen, which swells its volume with out in any way contributing to its heating power. It has been my endeavor for some time to construct a gas producer which, without losing the simplicity of the first, should be capable of yielding a heating gas of superior calorific power. The orifice at the bottom of the appaThis producer consists of a wrought- ratus may be enlarged and so arranged cylindrical chamber, truncated down that, instead of ashes only being prowards, and lined with brickwork. The duced, coke may be withdrawn, and in

and myself had to endure. The change from the use of solid to gaseous fuel would be the prelude probably to another, and still more important change, namely,

boiler. We are already in possession of gas engines working at moderate expense as compared with small steam engines, even when supplied with the comparatively expensive gas from our town gas mains, and all that will be required is an extension of the principle of operation already established. The realization of such a plan would, of course, involve many important considerations, and may be looked upon as one of those subjects the accomplishment of which may be left for the energy and inventive power of the rising generation of engineers.

this way a continuous coke oven may be constructed, which is at the same time a gas producer, or, in other words, an apparatus in which both the solid and gaseous constituents of the coal are fully the entire suppression of the steam utilized. The intense heat in the very center of a large mass of fuel has for its result a very rapid distillation, and thus one gas producer does the work of two or three gas producers of the type hitherto employed; this more concentrated action will moreover allow of the introduction of gaseous fuel, where want of space and considerations of economy have militated hitherto against it, and in favor of the ordinary coal furnace. It has been already proved that steam boilers can be worked economically on land with gaseous fuel, and there is no reason that I know of why the same Before leaving this branch of the submode of working should not also be ap- ject, I wish to call attention to a favorite plied to marine boilers. 'The marine suggestion which I had occasion to engine has within the last fifteen years make some years ago. It consists in been improved to an extent which is placing gas producers at the bottom of truly surprising; the consumption of the coal mines themselves, so that incoal, which at the commencement of that stead of having to raise the coal by meperiod was never less than 8 lbs. per chanical power, the combustible gases horse power, has been reduced by ex- ascending from the depth of the mine to pansive working in compound cylinders the surface would acquire by virtue of to 2 lbs. or even less per actual horsepower. The mode of firing marine boilers has, however, remained the same as it was in the days of Watt and Fulton. In crossing the Atlantic one may see a considerable number of men incessantly employed in the close stoke hole of the vessel opening the fire doors and throwing in fuel. Each charge gives rise to the development of great clouds of black smoke issuing from the chimney, to the great annoyance and discomfort of the passengers on deck. If, instead of this, the fuel could be discharged mechanically into one or more gas producers, the gaseous fuel produced would maintain of the daily traffic. the boilers at a very uniform heat, with- I now approach another and the last out necessitating the almost superhuman portion of my address, the attainment toil of the firemen; no smoke or dust of very intense degrees of heat either would be emitted from the chimney, and for effecting fusion or chemical decoma large saving of fuel would be effected. position. Although by means of the This change would be specially appre- combustion of either solid or gaseous ciated by the numerous tourists visiting fuel heats are produced which suffice for the Western Highlands. Speaking from all ordinary purposes, there is a limit my own experience on one occasion, I imposed upon the degree of temperamay say that the pleasure of a trip on ture attainable by any furnace dependthe beautiful Loch Lomond was very se- ing upon combustion. It has been riously marred in consequence of the shown by Bunsen and by St. Claire Defumigation which my fellow-passengers ville, that at certain temperatures the

their low specific gravity such an onward pressure that they could be conducted in tubes to distances of many miles, thus saving the cost of raising and transporting the solid fuel. Glasgow, with its adjoining coal fields, appears to me a particularly favorable locality for putting such a plan to a practical trial, and the well-known enterprise of its inhabitants makes me sanguine of its accomplishment. When thus supplied with gaseous fuel, the town would not only be able to boast of a clear atmosphere, but the streets would be relieved of the most objectionable portion

pounded charcoal or other bad conductor of heat. A hole is pierced through the bottom of the crucible for the admission of a rod of iron, platinum, or dense carbon, such as is used in electric illumination. The cover of the crucible is also pierced for the reception of the negative electrode, by preference a cylinder of compressed carbon of comparatively large dimensions. At one end of a beam supported at its center is suspended the negative electrode by means of a strip of copper, or other good conductor of electricity, the other end of the beam being attached to a hollow cylinder of soft iron free to move vertically within a solenoid coil of wire, presenting a total resistance of about 50 units or ohms. By means of a sliding weight the preponderence of the beam

chemical affinity between oxygen on the one hand and carbon and hydrogen on the other absolutely ceases, and that if the products of combustion CO, and H.O be exposed to such a degree of temperature they would fall to pieces into their constituent elements. This point of dissociation, as it is called, is influenced by pressure, but has been found for CO, under atmospheric pressure to be 2600 C, (or 4700° Fahr.). But long before this extreme point has been arrived at, combustion is greatly retarded, and the limit is reached when the losses of heat by radiation from the furnace balance its production by combustion. To electricity we must look for the attainment of a temperature above that of dissociation, and we have evidence of the early application of the electric arc to such a purpose. In 1807 Sir Humphrey Davy suc- in the direction of the solenoid can be ceeded in decomposing potash by means varied so as to balance the magnetic of an electric current from a Wollaston force with which the hollow iron cylinder battery of 400 elements, and in 1810 he is drawn into the coil. One end of the surprised the members of the Royal In- solenoid coil is connected with the posistitution by the brilliant electric arc pro- tive, and the other with the negative pole duced between carbon points through of the electric arc, and, being a coil of the same agency. Magneto-electric and high resistance, its attractive force on dynamo-electric currents allov of the the iron cylinder is proportional to the production of the electric arc much electro-motive force between the two more readily and economically than by the use of Sir Humphrey Davy's gigantic battery, and Messrs. Huggins, Lockyer and Liveing, and other physicists, have taken advantage of the comparatively new method to advance astronomical and chemical research with the aid of spectrum analysis.

electrodes, or, in other words, to the electrical resistance of the arc itself.

The resistance of the arc was determined and fixed at will within the limits of the source of power, by sliding the weight upon the beam. If the resistance of the arc should increase from any cause, the current passing through the My object is now to show that the solenoid would gain in strength, and the heat of the electric arc is not only avail- magnetic force overcoming the counterable within a focus, or extremely con- acting weight, would cause the negative tracted space, but that it is capable of pro- electrode to descend deeper into the cruducing such larger effects as will render cible; whereas, if the resistance of the it useful in the arts for fusing platinum, are should fall below the desired limit, iridium, steel, or iron, or for effecting the weight would drive back the iron such reactions or decompositions as re- cylinder within the coils, and the length quire for their accomplishment an in- of the arc would increase, until the baltense degree of heat, coupled with free-ance between the forces engaged had dom from such disturbing influences as been re-established. Experiments with are inseparable from a furnace worked long solenoid coils have shown that the by the combustion of carbonaceous material. The apparatus which I employ to effect the electro-fusion of such material as iron or platinum consists of an ordinary crucible of plumbago, or other highly-refractory material, placed in a metallic jacket or outer casing, the inter- This automatic adjustment of the arc vening space being filled up with is of great importance to the attainment

attractive force exerted upon the iron cylinder is subject only to slight variation within a range of several inches, which circumstance allows of a working range to that extent of nearly uniform action. on the electric arc.

of advantageous results in the process ble might be interfered with through the of electric fusion; without it the resist- detachment of particles from the dense ance of the arc would rapidly diminish carbon used for the negative pole, alwith increase of temperature of the though its consumption within a neutral heated atmosphere within the crucible, atmosphere is exceedingly slow. and heat would be developed in the dy- prevent this I have used, both in this connamo-electric machine to the prejudice nection and also in the construction of of the electric furnace. The sudden electric lamps, a water pole, or tube of sinking or change in electrical resistance of the material undergoing fusion would, on the other hand, cause sudden increase in the resistance of the arc, with a likelihood of its extinction, if such self-ad. justing action did not take place.

copper, through which a current of water circulates, so that it yields no substance to the arc. It consists simply of a stout copper cylinder closed at the lower end, having an inner tube penetrating to near the bottom for the passage of a current of water into the cylinder, which water enters and is discharged by means of flexible india-rubber tubing.

material, and its sectional area small, the escape of current from the pole to the reservoir is so slight that it may be neglected. On the other hand, some loss of heat is incurred through conduction, with the use of the water pole, but this loss diminishes with the increasing heat of the furnace, inasmuch as the arc becomes longer, and the pole is retired more and more into the crucible cover.

Another important element of success in electric fusion consists in constituting the material to be fused the positive pole of the electric arc. It is well known This tubing being of non-conductive that it is at the positive pole, that the heat is principally developed, and fusion of the material constituting the positive pole takes place even before the crucible itself is heated up to the same degree. This principal of action is of course applicable only to the melting of metals and other electrical conductors, such as metallic oxides, which constitute the materials generally operated upon in metallurgical processes. In operating upon In the experiments which I shall now non-conductive earth or upon streams of place before you the current which has gases, it becomes necessary to provide a supplied the one electric lamp in the non-destructible positive pole, such as is center of the hall will be diverted by supplied by the use of a pool of fused means of a commutator through the elecplatinum, or iridium, or by a plumbago tric furnace. After it has been active crucible. In working the electric fur- for five minutes to warm the crucible, I nace, some time is taken up in the first shall charge it with 8 lbs.of broken steel instance in raising the temperature of files, which I shall endeavor to melt and the crucible to a considerable degree, pour out into an ingot mould before your but it is surprising how rapidly an accu- eyes. By some obvious modifications mulation of heat takes place. In using of this electric furnace, it can be made a pair of dynamo-machines capable of available for a variety of other purposes producing seventy webers of current where intense heat is required, combined with an expenditure of 7 horse-power, with immunity from disturbing chemiand which, when used for purposes of cal actions. By piercing a number of illumination, produce a light of 12,000 radial holes through the sides of the candles, a crucible of about 8 inches in chamber, and introducing the ends of depth, immersed in a non-conductive wires through the same, an excellent material, has its temperature raised to a means is provided of heating those wire white heat in fifteen minutes, and 4 lbs. ends very rapidly, without burning them, of steel are fused within another fifteen for the purpose of welding them tominutes, successive fusions being effected gether. The electrical furnace will also in somewhat diminishing intervals of be found useful, I believe, in the hands time. The process can be carried on on of the chemist, to effect those high tema still larger scale by increasing the perature reactions between gaseous bodpower of the dynamo-machines and the size of the crucibles.

The purely chemical reaction intended to be carried into effect within the cruci

ies which require the employment of temperatures far exceeding the hitherto available limits, and will thus increase the area of available reactions at his dis

posal for the attainment cf either scien- neglect the economical and sanitary contific or practical ends. ditions under which those ends were I have endeavored to compress within accomplished. The exhibition, which the limited space of a single lecture sub- has lately been held in this city, of apject matter that might occupy the close pliances for heating and illuminating by attention of the student for weeks or means of gas and electricity, in which months; and I may, therefore, be par- your President, my esteemed friend, Sir doned if I have failed to convey to you William Thomson, took so prominent a more than a very rough outline of what part-as he does in everything tending may be accomplished by the judicious towards the advancement of human use of gaseous fuel, and of the electric knowledge and well being-proves how current, as heating agents. The one deep is the interest felt amongst you in purpose that has been foremost in my those very questions with which I have mind in preparing this lecture has been had to deal this evening. And so I to make war upon the smoky chimney- thought you might not be disinclined to which, so far from being a necessity un- give attention once more to a particular der any circumstances whatever, should view of the question, which happens to be regarded only as a remnant of that be the result of the independent labor stage of our industrial and social pro- of one who may claim, at any rate, to gress which, satisfied with the attain- have given a life-long attention to the ment of certain ends could afford to subject.

THE EFFECT OF PUNCHING ON STEEL AND IRON PLATES. From "The Engineer."

WE referred recently to certain experi- drilled subsequently, or it can be first ments made by the Board of Trade on drilled, and then punched. The value of steel plates for boilers and ships. The all the three first-named systems has most prominent feature in Mr. Trail's been repeatedly tested, but no one has report is the absence of information on tested the fourth, and yet it appears to those points which most perplex en- have much to recommend it. It is well gineers and shipbuilders; and before we known that when a plate is punched the have done we hope to make this fact hole is always a little conical, and this very clear, in the hope that others will conical shape is of much value, because take new ground, and quit the beaten it relieves the rivet head or point to path of experiment, which, it may now some extent of strain, and even though be safely said, cannot lead us to a knowl- the head should fly off the rivet is still edge of that which we wish to know. It useful. Drilled holes are not conical, will be remembered that all the plates and this is admitted to be a serious tested were pulled asunder by Mr. Kirk- objection to them, and besides they are aldy, and the results obtained, although expensive. Now, if plates requiring in many respects new to many persons, such holes were first drilled to, say, in., are just what were anticipated by those and then punched up to the proper who have made steel a special subject of dimensions, say 1 in., the cost of drillstudy. But, although this is true of ing would be reduced, and the conical most of the results obtained it is not punched hole would be obtained. It true of all; and some of them are op- remains to be seen whether under such posed in a small degree to those obtained conditions the plate would or would not by other inquirers. It is of the utmost be weakened by the punching; as on importance that the effect produced on a this point we possess no information we plate by making holes in it should be must content ourselves with suggesting understood very plainly. There are to any one about to test steel the advisfour ways in which a rivet hole may be ability of trying what would be found a made. It can be punched, or it can be very simple experiment. As regards the drilled, or it can be punched first and other three systems, the Board of Trade