The quantity of gas admitted requires to be regulated to the size of the lamp flame, for if the gas be in excess, the lime will be cooled down and the light diminished. A similar loss of light will result from having too little gas; so that some attention will be required to enable the operator to adjust the apparatus satisfactorily.
The wick should be carefully put into the wick-holder in straight lengths, not twisted together, and not too tightly packed. A slight separation should be made in the top of the wick to allow the stream of gas to pass freely. The point of the jet should be about one-tenth of an inch below the top of the wick, and should not project into the wick. The wick should be kept up close to the point of the _jet_, and not be allowed to bend towards the _lime cylinder_.
The spirit to be used with the oxycalcium lamp is to be alcohol or the best methylated spirit; paraffin spirit will not do. It is best to renew the wick each time the lamp is used.
It is now necessary to describe the other form of oxycalcium light--the oxycalcium _jet_.
The oxycalcium jet is shown at Fig. 6, and it will be seen that the cistern and wick-holder required by the oxycalcium lamp are both dispensed with. There are, instead, two horizontal tubes lying side by side, each having a stopcock at one end, the other end of each tube being turned up, one--the hydrogen tube--at right angles and inserted into the stem of a sort of oblique T-shaped tube. The end of the other horizontal tube--the oxygen tube--is bent into a bow form, so that it may pass through the crosspiece of the oblique T-shaped tube before mentioned. The stopcock of the oxygen tube is to be connected with the bag containing the oxygen gas, and the stopcock of the hydrogen tube is to be attached by a flexible tube to any of the gas-fittings in the room where the apparatus is to be used. By this arrangement a stream of ordinary hydrogen or street gas will pass through the hydrogen tube into the oblique T-shaped tube, and will issue out at its open end, where it is to be lighted. This flame, by the action of the stream of oxygen issuing from the end of the oxygen tube, will be forced against the lime cylinder, and produce, as in the former case, the oxycalcium light. The same attention to the adjustment of the quantity of oxygen gas to the size of the hydrogen flame that was necessary for the oxycalcium lamp is equally needed with the oxycalcium jet, and by means of the two taps this can be managed with the greatest facility. It is usual to drill a hole through the flat part of the key of the oxygen stopcock, so that it may be readily distinguished. It sometimes occurs that the gas-fittings from whence the supply of hydrogen is to be obtained have immovable nipples. In this case it will be found advantageous to connect, by means of a T-piece, two or even more of the nipples with the tube that is to convey the hydrogen to the jet; closing, of course, those that are not thus used.