ioo SCIENTIFIC APPARATUS. 



monochord of Pythagoras we have an early machine which still 

 remains of value. The " Pythagorean comma " is in frequent 

 reference to this day, and his division of the string, followed by 

 Euclid in the " Sectio Canonis," laid a foundation to the mathe- 

 matical theory of music. 



The Organ, whether in the hydraulic or pneumatic form, is the 

 only other instrument involving scientific and mechanical con- 

 struction which dates back to classical times. In the Hydraulic 

 Organ, the principle of which is exhibited, fluid pressure was used 

 to compress the air. 



Whilst the monochord has, from the earliest times, illustrated 

 the laws of strings, pipes have had no corresponding representa- 

 tive among scientific apparatus. 



The organ itself, however, is essentially a great collection of 

 apparatus whereby the tones of other instruments are imitated. 

 We can easily recognise the characteristics of flute, trumpet, horn, 

 voice, or string. Thus, while analysis of tone is- modern, the 

 artificial composition of tone has long been practised in organ 

 pipes, and may still be advantageously studied in them ; indeed, 

 the mixture stops, known as " cornets " in old organs, were really 

 an instinctive anticipation of Helmholtz's discoveries as to quality 

 or timbre. 



The materials of a pipe are either wood or metal, according to 

 the form desired wood being clearly suited for rectangular pipes, 

 and metal for those of rounded or conical outlines ; the material 

 being selected more for the sake of solidity than for its influence 

 upon tone. 



Pipes fall into one of two great classes flue and reed pipes 

 according to the mode in which the column of air is excited. 



In flue-pipes the exciting cause is a sheet of wind passing over 

 a mouth, exemplified in the case of a common whistle, which is. 

 in fact, the representative of all flue-pipes. 



Pipes, like whistles, form three groups, according as they are 

 stopped at the end, half stopped, or entirely open. Each of 



