U8 REPORT — 1853. 



of Bath, each invented a pneumatic machine to act upon the manual valves, and, sin- 

 gular to say, they were both on the same principle, both had the same defects ; viz. 

 after the key was pressed down, a moment of time was lost before the corresponding 

 pipe emitted any sound ; this, in rapid music, although an apparent trifling diffi- 

 culty, must account for its not becoming in general use for large organs. The model 

 by Mr. Hamilton was exhibited before the members of the British Association at their 

 meeting in Birmingham in 1831. Mr. Barker (now resident in Paris) took out a 

 patent for his machine in France, since which he has made several improvements to 

 it ; further improvements have been made to it by the Chevalier Cavallee. 



The improvements now offered consist of a regulating screw and ball-valve, by 

 which means a more certain and instantaneous action is acquired ; also a perfectly 

 new system of centring the action, which is applicable to other parts of the mechanism 

 in organs, and by which means the friction is reduced to a nominal amount, and 

 noise entirely obviated. 



By the use of a peculiarly formed drill, where two pieces of wood are to be attached 

 together by means of a centre to form a moveable joint, the part that works in the 

 mortice has the surface completely cut away, with the exception of a small por- 

 tion, where the wire-centre passes through, which stands up rather proud, like a 

 small washer, on either side of the tenon; thus the large surface of the tenon is pre- 

 vented rubbing in the mortice at every movement of the joint. This drill (made 

 either for large or small work) may be used with very great advantage in the whole 

 of the mechanism of our organ, where two pieces of wood form a moveable joint. 



The next improvement is the introduction of a small stud, by which each lever or 

 square connected with the keys can be fixed separately; the old system is to pass a 

 wire through a range of from fifty to sixty squares or levers, which wire is secured to 

 a bar of wood by means of staples driven in fast. Should an accident occur to a 

 lever in a range or set, the whole of the machinery would have to be detached to get 

 to the damaged part, and this, in some instances, at a loss of several days' labour ; 

 whereas, by the new or improved system, the damaged part would be removed by 

 taking out a single screw, and replaced in as many hours as the old system would 

 occupy days. 



The next improvement is a new pedal-valve for large pedal pipes, to which I have 

 given the name of the " universal pedal-valve," in consequence of its being applicable 

 in any position in a simple box or wind-trunk, thereby doing away with the necessity 

 of a pedal sound-board with grooves. The advantages of this pallet is the large quan- 

 tity of wind it will allow to escape when open, and, being a ball-valve, the resistance 

 of the wind is in a great measure obviated : the expense of making it is less than the 

 old pedal-valve. 



On t/ie Steam- Engine Indicator. 

 By Joseph Hopkinson, Engineer, Huddersfield. 

 The indicator is a quarter of a square inch, and each tenth of an inch on the index 

 represents one pound pressure to the square inch on the piston of the engine. The 

 spring compressed is the steam pressure, and distended, is the atmospheric pressure 

 upon the piston of the indicator. This spring is so adjusted as to meet the require- 

 ments of the pressure as it increases. When the steam exceeds twenty-five pounds 

 to the square inch above the pressure of the atmosphere, there is an additional 

 spring enclosed in a case for higher pressure up to seventy-five pounds to the 

 square inch or any other pressure required, to be screwed on the top of the casing. 

 The piston rod of the indicator passes up the centre of the spring and comes in 

 contact with the top attached to the second spring, so that instead of the resistance 

 of only one spring, there is a resistance of two springs for high pressure steam. On 

 the scale for high pressure the distances are marked thirty to the inch for steam above 

 twenty-five pounds, and one-thirtieth of an inch represents one pound pressure to the 

 square inch on the steam side. The scale on the vacuum side is ten to the inch, 

 or one-tenth of an inch represents one pound pressure to the square inch, as before 

 with high or low pressure steam ; there is a hole in the side of the tap ; when the tap 

 is open the hole is turned with its perfect side against the plug ; but when the tap 

 is closed, the hole communicates with the piston of the indicator and allows the 

 pressure of the atmosphere to the piston. The paper is fixed round the body of the 

 instrument so as to be firm ; the pencil holder is then parallel with the cylinder, so that 



