Development of the Phonograph at Alexander Graham Bell's Volta Laboratory

record on the electro-type in the Smithsonian package is of the other form, where the vibrations are impressed parallel to the surface of the recording material, as was done in the old Scott Phonautograph of 1857, thus forming a groove of uniform depth, but of wavy character, in which the sides of the groove act upon the tracing point instead of the bottom, as is the case in the vertical type. This form we named the zig-zag form, and referred to it in that way in our notes. Its important advantage in guiding the reproducing needle I first called attention to in the note on p. 9-Vol 1-Home Notes on March 29-1881, and endeavored to use it in my early work, but encountered so much difficulty in getting a form of reproducer that would work with the soft wax records without tearing the groove, we used the hill and valley type of record more often than the other.

In 1885, when the Volta associates were sure that they had a number of practical inventions, they filed applications for patents