SCIENCE— ADYEBTISEMENTS 



A NEW FORM OF 



ORGAN PIPE 



Special Features Suggested by PROFESSOR LUNN, University of Chicago 



No. 3268. — DEMONSTRATION ORGAN PIPE. All Metal. Making it possible to teach a larger 

 number of the fundamental principles of organ pipes. 



The usual method of varying the length of a closed pipe is by a sliding piston. Frequently in 

 demonstrating this by sliding the piston it is found that one of the overtones will become more marked 

 than the fundamental and the pipe apparently changes pitch. This may sometimes be delayed by blow- 

 ing either more or less vehemently. But it has been proven that with the range of lengths usually used 

 in class demonstration work, it is impossible to make an organ pipe that will not emphasize some over- 

 tone at some length. To produce the fundamental at different lengths the mouthpiece must be changed 

 in construction. 



This instrument has an adjustable mouthpiece. By operating the two sliding cylindrical sleeves the 

 amount and direction of the air jet may be changed and also the size of the opening between the 

 resonance column and the outside air. 



By this method a demonstration of the law of lengths may be made witliout producing overtones 

 — by adjusting the mouthpiece while operating the piston. 



Further, the overtones, first, second, third, etc., may be produced at will, without changing the pres- 

 sure of the blast of air or the length of the resonance column. In this design of organ pipe these 

 overtones are brought out by altering the position of the sleeves over the windway. This demon- 

 strates one of the most technical problems in the art of organ building, and also shows very forcibly 

 the reason for so-called "lip-positions" in many wind instruments. 



The piston is provided with graduations so that the exact length of air coluirm may be readily 

 known at all times. The air column length is a little more than 40 cm. Therefore the pitch range 

 will be from about C up to very high pitches determined by how short the air column may be made 

 to resonate. The pitch obtained at any length varies by overtone steps depending upon the positions 

 of the sleeves about the windway. The lowest note that can be sounded is produced by pulling the 

 piston all the way out and making an open tube, and is of course an ottave lower than the lowest note 

 for a closed pipe. The height of the mouth will be found to be required to be less when the pipe is 

 an open pipe than when it is a closed pipe. 



Handsomely Nickel 

 Plated. About 60 cm. 

 long. 



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 of other new developments 

 in Scientific Apparatus. 



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W. M. WELCH SCIENTIFIC COMPANY 



1516 Orleans Street 



Manufacturers, Importers and Exporters of 

 Scientific Apparatus and School Supplies 



Chicago, m., U. S. A. 



