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Account of Experiments on on Conversation tubes*

Nov 10 1793
Account of the Experiments on which hitherto as have been been made for
for the purpose of ascertaining to what distance for conversation may be carried on
practicability carrying on
which the idea of making use of Paper for conversation
with secresy by means of through tubes or tubes of or the betweenby persons stationed at the opposite
at any given requireddistance, must at one oor more stations according
in a low voice through a tube, between two persons stationed at the respective ends.
In the distance has been grounded indicated

Experiments made At the distance of 366 feet a low voice atbelow the pitch of under the tone of
ordinary conversation was distinctly heard. The person whose voice
characteristic tone peculiar tone quality of the voice indicative characteristic
of the speaker was perfectly distinguishable.

The tube was composed of such lengths as were at hand viz:Base | Length Inch | Feet 0 3/4 | 108 1:0 | 222 1:1/4 | 36 Total | 366
* They might be called Telacoustic (τηλε from afar [Greek text] to hear) or cryptacoustic (μουπττον secretly) or Cryptaphonic (φονεο to Speak). Speaking Trumpets, called Stentorophonic, require the voice to be raised, exclude secresy, and serve only for limited distances. Length 3/4 108 1 202 11/4 36 - 366 In this length were included three right angles (three rectangular
junctions) besides
a pretty sharp curved bend.
A very gentle tap, made at one
end with a pencil, was distinctly
heard at the other.

They might be called Telacoustic
from two Greek words
([Greek text] from afar, [Greek text] to hear)
or Cryptophonic [Greek text] secretly [Greek text]
They are to be distinguished from the
Speaking Trumpets called Stentorophonic (to speak)
tubes, which require the voice
to be raised, exclude secresy, and serve only
for limited distances

Through a tube of 80 feet in length being
Through so great a part of the tube thus compounded was of no more than 3/4 inch bore, a
no more that 1/2 an inch in diameter the voice had been found
tube of 1/2 inch bore had been found totallly incompetent to the purpose. AtThrough a length of no more than
totally inaudible, though the two ends of two ends of, both ends of the tube were in the same
80 feet the voice was totally inaudible, though both ends of the tube were in the same
room, and no sudden bend in it the tube. To what degree the audibility
increases with the borediameter of the tube, and where the progressionincrease
stops, would be interesting to know, but has not there yet been triedof course could not be tried without.
considerable expence.
A good deal appeared to depend upon the form given to the tube at
the very exit. This would of course might soon be thoroughly discussed and settled , which it might
soon be, & at small expence.

In the above length of 366 foot were included three right angles
besides three rectangular junctions besides a sharp curved

At that distance of any gentle tap with a pencilmade at one end was distinctly
heard at the other

Cassual Experiment at a Mile's Distance Intimation had been received from good authority, though not from the first hand from Mr Maurice the Mathematical
Instrument Maker of an instance where a Voice to the great surprise of the hearer was accidently heard at the distance
of upwards of a mile by means of an a leaden water pipe of that length. This If the idea
should be thought worth attending to the relation wouldmight be traced out to the fountainhead & the particulars ascertained

---page break---

Identifier: | JB/106/007/001
"JB/" can not be assigned to a declared number type with value 106.


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experiments on conversation





copy/fair copy sheet

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sir samuel bentham



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