LIMELIGHT 95 



3. To transmit blue light A =4360 A.U., and also the 

 violet lines 4070 and 4050 A.U. 



Copper sulphate . . . .1 gram. 

 Distilled water .... 225 c.c. 

 Ammonia -880 . . . .75 c.c. 



LIMELIGHT. Limelight is so largely used among 

 lanternists that many who take up photomicrography will 

 have it at hand, and will find the ordinary lantern jets 

 quite satisfactory for the purpose, when used with hard 

 limes. There are three types of jet, "Blow-through," 

 "Mixture," and "Injector." The blow-through are the 

 simplest, but the mixture jets give the most powerful 

 light ; the latter require both the oxygen and hydrogen 

 under pressure in cylinders, and the gases mix in a chamber 

 in the jet. The Gwyer is an excellent mixture jet and 

 gives a brilliant light. For most purposes the blow-through 

 jets are preferable because of their greater safety and 

 simplicity ; hydrogen is seldom used with them, as coal 

 gas from the mains is an efficient substitute, and requires 

 no cylinder. Oxygen is always obtained under pressure 

 in cylinders, which should be fitted with a regulator. 

 The oxygen is connected to the inner jet of the blow- 

 through burner, and the coal gas to the outer annular 

 tube. The coal gas is first lighted and turned fairly well 

 up to play over the lime, the tap connecting the oxygen 

 cylinder to the regulator is then opened slightly more 

 than will be needed to supply a sufficient current of 

 oxygen. The regulator having thus been put in connec- 

 tion with the cylinder, the tap connecting it to the jet is 

 opened, and then the tap of the jet itself, which last is 

 used to regulate the flame. Efficient regulation cannot 

 be obtained if the oxygen is admitted straight through to 

 the jet without previously connecting the cylinder to the 

 regulator. If coal gas and hydrogen are unobtainable an 

 ether saturator may be used in connection with a blow- 



