THE INCUBATOR 43 



6. Push the lead weight on the lever quite to the left. 



7. See that the needle below the milled head-screw P 

 rests in the depression in the lower end of the screw. 



8. Withdraw the by-pass screw S and the milled head- 

 screw P three or four turns, then turn on the gas both at 

 the service and under the lantern, and light it. 



9. With one hand lift the lever D as high as it will go 

 comfortably, but without puttiag any strain upon it. With 

 your other hand turn the screw S in again until the flame 

 is reduced to less than the size of an ordinary pea. 



10. Eelease the lever, and as it falls the gas will suddenly 

 rise to its full height. 



11. Turn the milled head-screw P in the direction to 

 raise the lever, and continue to do so until the flame is 

 reduced to the same size as it appears when you hold the 

 lever up with your hand. 



12. Now give the milled head-screw P one half-turn back- 

 wards, and the gas will again rise to its full height. 



13. By means of the cock below the lantern, reduce the 

 flame to about the size of the bowl of an ordinary egg- 

 spoon. 



14. Shut the doors of the incubator and gently lower 

 the thermometer down the brass-bushed hole near the 

 Excelsior valve. 



15. Put on the short glass chimney to protect the flame 

 from draughts. 



16. The flame in the lantern will now remain constant 

 until the lever is pushed up by the expansion of the 

 capsule. 



17. When this is the case, the flame will decrease auto- 

 matically until it is reduced to that size which shall supply 

 just the amount of heat required to keep the interior at the 

 temperature now indicated on the thermometer. 



18. If after a lapse of some hours it is found that the 



