6 PHOTO-MICROGRAPHY 



neatly compiled that with their permission we repeat them at length, as they apply 

 almost equally well to any other form of mixed jet. 



" I. Always work up the light by increasing the hydrogen side first, then 

 increasing the oxygen until the best light is obtained for that amount of hydrogen, 

 and repeating this until the jet very slightly roars. Then reduce by turning the 

 oxygen down first very slightly, then the hydrogen until the light is at its best and 

 perfectly silent. 



2. — Always work the taps very slowly and steadily when it is important to get 

 the highest results. 



3. — Attend carefully to the distance of the lime from the nipple of the jet, and do 

 not forget that the more gas you turn on the greater the distance must be between 

 the lime and the nipple, or you will get a black spot on the centre of the lime instead 

 of a bright one. This is done after you have adjusted your taps by working the lime 

 backwards and forwards until you have the light at its best. Roughly speaking, 

 for a low pressure about |- inch will not be far off, gradually increasing the distance to 

 f or J inch, as you open the jet taps more and more to increase the light. 



4. _For the most powerful fight, rack the lime up until the jet plays almost 

 upon the bottom of the lime cylinder, which should be rendered incandescent right 

 up to the top, and where it is imperative to maintain light for a long time at the 

 utmost power, it will be preferable to remove lime with the tongs and invert it 

 rather than lower the level very much, so that no portion of its incandescent spot may 

 be sacrificed. 



5. — For the greatest light use large limes of medium hardness, but when only a 

 moderate light with extreme economy of gas is required, it will be far better to use a 

 medium-size lime ; very large hard limes do not yield such a rich light with a very 

 low pressure of gas as a moderately hard medium-size Hme ; on the other hand, such 

 limes must be turned frequently when used with full pressure of gas, and when 

 working the jet at its utmost power. The smaller the bore of the nipple the quicker 

 the pitting of the lime. 



6. — Do not forget to rime out the hole in the lime until it will drop easily upon 

 pin ; if limes are forced down slightly upon the jet pin the expansion of the pin when 

 heated must crack or burst the lime. 



7. — If the jet becomes unduly hot by firing back it is probably leaking some- 

 where. Test the tap and front tube carefully : a very slight leak will cause trouble 

 with a tV bore nipple. 



8. — The Gwyer Jets will dissolve perfectly with a nipple even up to bore if the 



