There have been many discussions on the reason for these balls and spires, also known as finials, however they seem to overcomplicate the matter by suggesting they were filled with mercury or some other kind of substance. I believe there may be a simpler function that is being overlooked.
Cavity Resonance.
Build a cavity with a set shape and funnel and it will create a specific frequency when vibrated.
So how was it vibrated? That's where St. Elmo's fire comes in. St. Elmo's fire is a corona discharge induced by a high difference in potential, or voltage. For anybody who isn't already aware and is reading this thread. The voltage in the atmosphere increases about 100v for every meter.
With a tall spire and a good ground, that's quite a lot of potential difference. The potential difference can be increased further with a good ground and many older churches and cathedrals were built over aquifers and wet ground is a much better conductor than dry ground. The potential difference in the atmosphere may have been even higher when the buildings were originally built. You don't need that much to induce a corona discharge depending on the geometry of the shape at the top of the spire such as having sharp points.
So with a corona discharge, or St. Elmo's fire, you now have a have a source of vibration. If you've heard St. Elmo's fire it can create quite a hiss even if there isn't enough voltage to make it visible. The finial acts as a band-pass filter only allowing a specific specific frequency through. Underneath the cavity resonator is a horn shape to amplify the frequency coming out.
Understand that any modern instance of these is going to be a skeuomorph, that is they are simply ornamental as people have forgotten, or were made to forget, their original function but knew that this is the shape that you put on top of a spire to finish it off. So I doubt there is any working example on any church or cathedral as they have all been replaced or tampered with.
This ties in with the theory that cathedrals and churches were places of healing. They created frequencies and the building was designed to reverberate that frequency. Some may have had different frequencies such as St Basil's cathedral as can be noted by the different sizes of the resonators. Perhaps each room was used to heal different problems? The fact is people knew these were places of healing even after Christianity took over and the original reason was forgotten.
This website can help with understanding how the frequency can be calculated: Cavity Resonance
Cavity Resonance.
So how was it vibrated? That's where St. Elmo's fire comes in. St. Elmo's fire is a corona discharge induced by a high difference in potential, or voltage. For anybody who isn't already aware and is reading this thread. The voltage in the atmosphere increases about 100v for every meter.
So with a corona discharge, or St. Elmo's fire, you now have a have a source of vibration. If you've heard St. Elmo's fire it can create quite a hiss even if there isn't enough voltage to make it visible. The finial acts as a band-pass filter only allowing a specific specific frequency through. Underneath the cavity resonator is a horn shape to amplify the frequency coming out.
This ties in with the theory that cathedrals and churches were places of healing. They created frequencies and the building was designed to reverberate that frequency. Some may have had different frequencies such as St Basil's cathedral as can be noted by the different sizes of the resonators. Perhaps each room was used to heal different problems? The fact is people knew these were places of healing even after Christianity took over and the original reason was forgotten.
This website can help with understanding how the frequency can be calculated: Cavity Resonance
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