204 ON SUPEEHEATED STEAM. 



and lastly, if hydrogen did form, it would only 

 occupy tlie same space, and have the same force, 

 and obey the same expansive laws as sub- saturated 

 steam. A gentleman who works one of the vul- 

 canizers put on to it a pressure-gauge, thinking 

 I had not done so. He said he found the pressure 

 to be 50 or 60 lbs. to the square inch. I told him 

 to try the experiment with 2 lbs. to the inch. 

 That, he found, spoiled his work. Another gen- 

 tleman said it was not superheated steam if it 

 were 60 lbs. to the inch ; and asked, would it not 

 be just as dangerous as a boiler ? I had to refer 

 him to the fact, that steam could be superheated 

 at high as well as at low pressure, and that, with 

 sub-saturated steam, no explosion of the vul- 

 canizer, as fitted, could take place. 



It remains to be mentioned, that the thermo- 

 meters should, in all kinds of such apparatus, have 

 their tubes to extend at least one third of their 

 length into the apparatus, and that the tube should 

 be filled with mercury or oil. Thermometers with 

 the bulb inserted a very short length, I have found 

 indicate 15° less than the heat of one inserted a 

 longer length. 



In conclusion, I would just speak of patents 

 connected with this subject, as dentists, like all 

 other people, prefer to have all the advantage 

 without the drawback, and patents are great 

 drawbacks. I for one, although having had a 

 great deal to do with patents, both of my own and 



