THE LIME-LTGHT 61 



rotated by the cog-movement on a screwed pin, It not only 

 has a tendency to stick fast, but it scarcely rises with an entire 

 revolution, and the movement has to be continued for many 

 rapid revolutions to bring a fresh ring of the lime surface into 

 play. Hence a good ' blow- through,' or oxy-gas jet, will often 

 equal the light of such a mixed jet. The performance can be 

 greatly improved by clearing out the gauze to leave a free 

 passage, and attending to the jet as presently described. But 

 more than 350 candles can scarcely be got from such jets, and 

 with this gain in power the inconvenience of adjusting the 

 lime becomes much greater, as it has to be oftener made. 

 A good lime-turning movement should raise the lime 

 sufficiently, at every revolution, to bring the required new 

 zone before the jet. 



What is called the ' improved ' arrangement amongst 

 London opticians answers fairly well, the cog wheel being 

 made to turn a barrel with a square hole, through which the 

 squared lower end of the lime spindle slides freely, whilst a 

 treble-threaded screw on the upper part works in the brass 

 frame of the combination. The mixing-chamber into which 

 the gas-tubes deliver the gases is also rather larger in these 

 jets, which can often be made to give a very good light, 

 especially by taking out the gauze. If they do not, or if more 

 light is desired, or if, as is often the case, they whistle or roar 

 under good pressure, they must be attended to, and it is always 

 worth while to spend a little trouble over a well-made jet. The 

 tap-plugs should be taken out to see that they are not choked 

 by tallow, as is sometimes the case. Whistling or roaring is 

 generally due to some roughness in the nipple, or end of the 

 tube bearing it. To remove this the nipple should be taken 

 off, and a watchmaker's broach twirled round in it, which will 

 smooth out the bore itself ; and any roughness in the larger 

 bore below, or at the end of the tube, should also be cleaned 

 down with a tapered steel rimer. Filially a steel needle should 

 be taken, rather smaller than the bore, and twirled well between 



