"The audible has been conquered in my instruments to that extent which brings me into sympathetic contact with the inaudible, the vitalized conditions of which as regards sympathetic union with the terrestrial are the pure and only essentials necessary towards establishing the sensitive link, between the instrument and terrestrial chord-masses, in order to run sympathetic machinery. But there is still before me a vast region to be explored before the keystone of this sympathetic arch is set in position to carry the high order of sympathetic transfer that I aim at. I have every reason to hope that when I have mastered these mechanical difficulties I shall be able to control this most subtle of Nature's forces. When this is done, the commercial engine will soon follow. There is no truer nor quicker way to reach that end than the one I am now pursuing. My obligations on this line once fulfilled, I shall be at liberty to turn my attention to the consideration of the mental forces associated with the physical, and in fact the solution of the mechanical problem is one and the same in principle, as is the physical and mental. When one is solved all is solved. The convolutions which exist in the cerebral field are entirely governed by the sympathetic conditions that surround them.
" [Keely, Vibratory Physics - The Connecting Link between Mind and Matter
The word "arch" is encountered in Keely's Acoustic Charts.