The lime-holder of the oxyhydrogen jet is made to slide, so as to be capable of being moved towards or away from the point of the jet. This adjustment is necessary to rectify any slight difference in the diameter of the lime cylinders, for, in order to obtain the full amount of light, the face of the lime cylinder requires to be brought as close to the point of the jet as it can be without being in contact with it. In addition to this movement, the stem on which the lime cylinder is supported is also made to revolve, in order to provide a fresh surface of lime to be presented to the action of the flame. The heating power of the flame of the oxyhydrogen gases is so intense that a cavity is soon burnt in the face of the lime cylinder, and if this part of the cylinder were to be allowed to continue opposite to the jet, the light would be greatly diminished and the general effect marred. To provide against this, the stem of the lime-holder is made with a screw at its lower end, this screw working in a corresponding socket, so that by turning the stem of the lime-holder round on its axis a second motion in a perpendicular direction is also given to it. By this means the face of the lime passes before the point of the jet in a spiral direction, and consequently the same part of the lime cylinder is not brought a second time under the action of the flame. In order to facilitate the rotation of the lime cylinder, the screw is sometimes set in motion by clockwork; but the better plan is to turn the lime by means of a horizontal rod with bevel wheels.
Having described the various forms of apparatus constructed for producing the lime-light by means of oxygen and hydrogen gases, a few general observations will not be out of place. It should be borne in mind that oxygen gas is a supporter of combustion, and is neither explosive nor inflammable. The hydrogen gas will ignite, but will only do so in the presence of oxygen. With the oxycalcium lamp and oxycalcium jet, there is complete safety from explosion. In the oxyhydrogen jet there is also complete safety if care is taken not to fill up the hydrogen-bag with oxygen, and _vice versâ_. Such an admixture is explosive, and nothing can prevent an explosion when a light is applied. The contents of one bag will not pass into the other during an exhibition, and even if the weights were to fall off the bags, the only effect would be to put the light out.