CATALOGUE OF THE MECHANICAL ENGINEERING COLLECTION. 19 



Prints of James Watt's Steam-Jacketed Single-Acting Cylinder. Photome- 

 chanical Print from the Model in South Kensington Museum. Two 

 Views. 



The engine consists of an external cylinder closed at top and 

 bottom, and an internal cylinder closed at top but opened at the 

 bottom and fitted with a piston. The steam entering the latter would 

 fill the part of the cylinder below the piston, also the space between 

 the two cylinders, hence the inside cylinder is a steam-jacketed cyl- 

 inder. A pipe connects the external cylinder to the separat con- 

 inder. A pipe connects the external cylinder to the separate con- 

 denser. Both the external and internal cylinders were made of tin 

 plate roughly soldered up. Watt complained from first to last of its 

 being leaky, and an experiment showed, as he expected, that it took as 

 much steam from the boiler regardless of whether it was working or 

 not. This model is presumed to be a very early one and may have 

 been Watt's first attempt with a steam- jacketed cylinder kept hot and 

 separate condenser kept cold. Cat. No. 180,623 U.S.N.M. 



Print from a Model in South Kensington Museum of a Two-Cylinder En- 

 gine for Double Action, 



In the patent of 1782- Watt states that there are various arrange- 

 ments that may be made of the several engines. 



A model in the South Kensington Museum is supposed to show a 

 transition state, or an attempt to produce a double-acting engine, by 

 two single-acting cylinders connected together by a chain over a 

 pulley. 



The print shows two single-acting vertical cylinders, their upper 

 ends connected by a passage without valves, their pistons having 

 single-acting valves opening upward, the eduction pipes entering 

 the bottom of each cylinder and having conical valves. Within the 

 eduction pipes is a small pipe terminating in a jet for injecting cold 

 water, thereby converting it into a condenser. There are also air 

 pumps for removing the water and air. Its action is as follows: 

 While the steam in the left cylinder is being condensed, it is also 

 entering the right cylinder, and, passing through the valve in its 

 piston and the connecting passage between the upper end of the 

 cylinders, it forces the left piston into the vacuum. When this 

 piston arrives at the end of its stroke, the steam and injected water 

 is reversed, a vacuum is formed under the right piston, and the steam 

 enters the left cylinder, etc. The drum or pulley over which the 

 chain passes is given a reciprocating motion which is communicated 

 to a beam or connecting rod by a long pin on the drum. 



Cat. No.180,627 U.S.N.M. 



