300 Sh' John Robison on the best Method of 



When the seat for the disk is turned out, the inside space be- 

 tween the inner and outer walls of the burner should be turn- 

 ed true for a quarter of an inch inwards, and no more shoul- 

 der should be left than just enough to support the disk in its 

 place. The disk should then be put into its seat, but not finally 

 fixed. The requisite number of holes should then be drilled 

 in it, and slightly counter-sunk to take off the barb. The disk 

 should then be reversed (that is to say, the counter-sunk face 

 should be put inwards), and finally fixed in its place. The 

 blaze which may have been pushed through with the drill will 

 now be on the outside, and may be easily removed by the file, 

 or by a slight counter-sinking, which is the preferable man- 

 ner, as the smooth-edged holes will keep longer clean than 

 those with a sharp arras, the application of an old tooth-brush 

 being sufficient to keep them in good order. 



The above observations apply chiefly to the illumination of 

 the interiors of buildings, and it may be proper to notice the 

 circumstances which require to be attended to in lights which, 

 being placed externally, are in some degree exposed to the 

 weather. The most important of these are the street lamps. 

 These may either be arranged at considerable distances, and 

 be fitted with powerful burners, or the intervals between them 

 may be smaller, and only a single jet be allowed for each. 

 Various local considerations must determine this, as well as 

 some other points ; but it should be kept in mind, that the 

 best small light is either the single jet of three inches and a 

 half or four inches high, or the fish-tail jet of three inches 

 high, and that for more powerful lights the argand is 2^>'e- 

 ferable \to all others. The large bat-wing, so much used in 

 large public lamps, is wasteful, smokes the lantern, and does 

 not give light in proportion to its expenditure. 



In most towns, framed square lanterns are used for street 

 lamps, as it is said that globes are apt to be obscured in cold 

 weather by the deposition of the water generated by the com- 

 bustion of the gas. It is no doubt true, that if proper precau- 

 tions be not taken, this inconvenience would be felt, and the 

 water which would trickle from the aperture in the bottom of 

 the globe would be liable to freeze in severe weather, and so 

 to close up the access for air, that the lamp would smoke or 



