SCIOPTICON MANUAL. 



157 



None of the accidents or annoyances above enumer- 

 ated have ever happened with the jet herein described. 

 Its characteristic flat mouth, small cavity, and ready 

 adjustments are in its favor, but may not be relied on 

 in spite of bad conditions. It will be observed that 

 this possibility of evil in the mixed jet, as distinguished 

 from Nos. 1 and 2, arises from the necessity of having 

 two gases in bulk, and from mixing them before coming 

 to the outlet. 



Ho. 1. 



No. 2. 



No. 8. 



THE THREE JETS presented above, side by side, show 

 what is peculiar to each. The oxygen tube of each is 

 screwed down upon its lead washer, so as to present its 

 flat mouth to the lime, as shown in "No. 3. 



When a very strong current meets with roughness at 

 the mouth of a jet, or strikes some impediment, or an 



