(under the class definition) Subject matter operated by steam from a receptacle charged with hot water under pressure, as distinguished from those in which pressure is generated within a boiler by the application of heat.
(1) Note. The charge of this subclass must come from an external supply and not be that collected in storage vessel or accumulator permanently a part of a heat operated plant to accommodate fluctuations in demand. For this subject matter see subclasses 652 and 659.
