LOSS OF LIGHT BY GLASS SHADES.
You will see on one of the lights I have here, a new swivel joint, which has been patented only within the last few days. The peculiarity of this swivel is that the body is made of two hemispheres revolving on each other in a ground joint. It will be made also with a universal movement; and its special advantage, either for gas, water, or steam, is that there is no obstruction whatever to a free passage—in fact, the way through the swivel body is larger than the way through the pipes with which it is connected. It can easily be made to stand any pressure, and if damaged by grit or dirt it can be reground with ease as often as necessary without deterioration, whereas an ordinary swivel, if damaged by grit, has to be thrown away as useless.
For meals, where a steam-kettle is not used, it is the best policy to have a cistern holding about 1½ pints for each man, and to boil this with a gas-burner. The lighting of the burner at a specified time may be deputed to a boy. If the men's dinners have to be heated, it is easy to purchase ovens which will do all the work required by gas at a much cheaper rate than by coal, if we consider the labor and attention necessary with any coal fire. Not that gas is cheaper than coal; but say we have 100 dinners to warm. This can be done in a gas-oven in about 20 minutes, at a cost for gas of less than 1d.; in fact, for one-fourth the cost of labor only in attending to a coal fire, without considering the cost of wood or coals. Gas, in many instances, is an apparently expensive fuel; but when the incidental saving in other matters is taken into consideration, I have found it exceedingly profitable for all except large or continuous work, and in many cases for this also. I only need instance wire card-making and the brazing shops of wire cable makers to show that a large and free use of gas is compatible with the strictest economy and profitable working.
Of all the tools in a workshop, nothing saves more time and worry than two or three sizes of good blowpipes and an efficient blower. I have seen in one day more work spoilt, and time lost, for want of these than would have paid for the apparatus twice over; and in almost every shop emergencies are constantly happening in which a good blowpipe will render most efficient service. Small brazing work can often be done in less time than would be consumed in going to the smith's hearth and back again, independently of the policy of keeping a man in his own place, and to his own work. The shrinking on of collars, forging, hardening, and tempering of tools, melting lead or resin out of pipes which have been bent, and endless other odd matters, are constantly turning up; and on these, in the absence of a blowpipe, I have often seen men spend hours instead of minutes. Things which need a blowpipe are usually most awkward to do without one; and men will go fiddling about and tumbling over each other without seeing really what they intend to do. They are content, as it all counts in the day's work; that it comes off the profits is not their concern. It will, perhaps, be new to many of you that blowpipes can easily be made in a form which admits of any special shape of flame being produced. I have made for special work—such as heating up odd shapes of forgings, brands, etc.—blowpipes constructed of perforated tubes formed to almost every conceivable shape; these being supplied with gas from the ordinary main and a blast of air from a Root's or foot blower. I have here an example of a straight-line blowpipe made for heating wire passed along it at a high speed. The same flame, as you no doubt will readily understand, can be made of any power and of any shape, and will work any side up; in fact, as a rule, a downward vertical or nearly vertical position is usually the best for any blowpipe. As an example of this class of work, I may instance the shrinking on of collars and tires, which, with suitable ring-burner and a Root's blower, could be equally heated in five minutes for shrinking on; in fact, the work could be done in less time than it would usually take to find a laborer to light a fire. When the rings vary much in size, the burners can easily be made in segments of circles. But then they are not nearly so handy, as each needs to be connected up to the gas and air supply; and it is, in practice, usually cheaper to have separate ring burners of different sizes. Of course, you will understand that a ½-inch gas-pipe will not supply heat enough to make a locomotive tire red hot, and that for large work a large gas supply is necessary. Our own rule for burners of this class is that the holes in the tube should be 1/8 to 1/10 inch in diameter, from ¼ to ½ inch pitch; and the area of the tube must be equal to the combined area of the holes. The gas supply-pipe must not be less than half the area of the burner-tube. Those of you who wish to study this matter further will, I think, find sufficient information in my paper on "The Construction of High-Power Burners for Heating by Gas," printed in the Transactions of the Gas Institute for 1883, and in the papers on the "Use and Construction of the Blowpipe" and "The Use of Gas as a Workshop Tool."
No doubt many of you have been troubled with the twisting of some special light casting, and will, perhaps, spend hours in the risky operation of bending an iron pattern so as to get a straight casting. A ladleful of lead and tin, melted in a small gas-furnace, will, in a few minutes, give you a pattern which you can bend and adjust to any required shape. It enables you to make trials to any extent, and get castings with the utmost precision. There is also this advantage, that a soft metal pattern can be cut about and experimented with in a way which no other material admits of. Awkward patterns commence with us with plaster, wax, sheets of wet blotting paper pasted together on a shape or wood; but they almost invariably make their appearance in the foundry after being converted into soft metal by the aid of a gas-furnace. I refer, of course, to thin, awkward, and generally difficult castings, which, under ordinary treatment, are either turned out badly or require a great amount of fitting. As an illustration of the use of this system of pattern-making, I have here two castings of my own, from patterns which, under the ordinary engineer's system, would be excessively costly and difficult to make as well as these are made. The surface is a mass of intricate pattern work and perforations. To produce the flat original, as you see it, a small piece of the pattern is first cut, and from this a number of tin castings are made and soldered together. From this pattern, reproduced in iron for the sake of permanence, is cast the flat center plate you see. To produce the curved pattern I show you, nothing more is necessary than to bend the tin pattern on a block of the right shape, and we now get a pattern which would puzzle a good many pattern-makers of the old style.
I will now show you by a practical utilization of the well known flameless combustion, how to light a coke furnace without either paper or wood, and without disturbing the fuel, by the use of a blowpipe which for the first minute is allowed to work in the ordinary way with a flame to ignite the coke. I then pinch the gas tube to extinguish the flame, allow the gas to pass as before, and so blow a mixture of unburnt air and gas into the fuel. The enormous heat generated by the combustion of the mixture in contact with the solid fuel will be appreciable to you all, and if this blast of mixed air and gas is continued, there is hardly any limit to the temperatures which can be obtained in a furnace. I shall be able to show you the difference in temperature obtained in a furnace by an ordinary air blast, by a blowpipe flame directed into the furnace, and by the same mixture of gas and air which I use in the blowpipe being blown in and burnt in contact with the ignited coke. In each case the air blast, both in quantity and pressure, is absolutely the same; but the roar and the intense, blinding glare produced by blowing the unburnt mixture into the furnace is unmistakable. The heat obtained in the coke furnace I am using, in less than ten minutes, is greater than any known crucible would stand. I am informed that this system of air and gas or air and petroleum vapor blast, first discovered and published by myself in a work on metallurgy issued in 1881, is now becoming largely used for commercial purposes on the Continent, not only on account of the enormous increase in the heat, and the consequent work got out of any specified furnace, but also because the coke or solid fuel used stands much longer, and the dropping, which is so great a nuisance in crucible furnaces, is almost entirely prevented; in fact, once the furnace is started, no solid fuel is necessary, and the coke as it burns away can be replaced with lumps of broken ganister or any infusible material. Few, if any, samples of firebrick will stand the heat of this blast, if the system is fully utilized. You will find it a matter of little difficulty, with this system of using gas, to melt a crucible of cast iron in an ordinary bed-room fire grate if the front bars are covered with sheet iron, with a hole (say) three inches in diameter, to admit the combined gas and air blast. The only care needed is to see that you do not melt down the firebars during the process. I will also show you how, on an ordinary table, with a small pan of broken coke and the same blowpipe, used in the way already described, you can get a good welding heat in a few minutes, starting all cold. In this case the blowpipe is simply fixed with the nozzle six inches above the coke, and the flame directed downward. As soon as the coke shows red, the gas pipe is pinched so as to blow the flame out, and the mixture of gas and air is blown from above into the coke as before. With this and a little practice, you can get a weld on a 7/8 inch round bar in 10 minutes.
There is one use of gas which has already proved an immense service to those who, in the strictest sense, live by their wits. In a small private workshop, with the assistance of gas furnaces, blowpipes, and other gas heating appliances, it is a very easy matter to carry out important experiments privately on a practical scale. A man with an idea can readily carry out his idea without skilled assistance, and without it ever making its appearance in the works until it is an accomplished fact. How many of you have been blocked in important experiments by the tacit resistance of an old fashioned good workman, who cannot or will not see what you are driving at, and who persists in saying that what you want is not possible? The application of gas will often enable you to go over his head, and do what, if the workman had his own way, would be an impossibility. When a man is unable or unwilling to see a way out of a difficulty, a master or foreman has the power to take the law in his own hands; and when a workman has been met with this kind of a reply once or twice, he usually gives way, and does not in future attempt to dictate and teach his master his own business. In carrying out this matter, it is not necessary that a specimen of fine workmanship shall be produced. A man usually appreciates the wits which have produced what he has considered impossible. In purely experimental work I think I may fairly state that the use of gas as a fuel in the private workshop and laboratory has done incalculable service in the improvement of processes and trades, and has played an important part in insuring the success and fortunes of many hundreds of experimenters, who have brought their labors to a successful issue in cases where, in its absence, neither time nor patience would have been available. I need only to call to your mind the number of new alloys which, for almost endless different purposes, have come into use during the last eight or ten years. I think the use of small gas furnaces in private workshops and laboratories may fairly be said to have enabled the experiments on most, if not all, of these alloys to be carried out to a successful issue.