GAS-PRESS URE REG ULA TORS. 127 



and the therm o- regulator. This apparatus has for its 

 object the maintenance of a constant pressure of the 

 gas going to the therrao-regulator. There are several 

 instruments of this form in use, but they do not accom- 

 plish the object for which they are designed. 



The instrument most commonly employed, the appa- 

 ratus of Moitessier (Fig. 30), is based on somewhat the 

 same principles as the large regulators seen at the 

 manufactories of illuminating gas. Such apparatus act 

 very well when employed on the large scale, as one sees 

 them at the gas-works ; but when applied to the limited 

 and sudden fluctuations seen in the gas coming from an 

 ordinary gas-cock, are practically useless. They are too 

 gross in their construction, and act only under compara- 

 tively great and gradual fluctuations in pressure. If a 

 good form of thermo-regulator be employed there is no 

 necessity for the use of any of the forms of pressure- 

 regulators thus far introduced. 



