NavList:

   

Reply

This topic is out of the scope of the list
but I want to correct some statements.
First of all, Thomson's name was William
(not David!) and this is the same Thomson
who later became Lord Kelvin.

After the first cable failed, the scientific
consultant was replaced by Thomson.

The main reason of the first cable poor characteristics
was its design. Physicists and engineers of that time
poorly understood physical and mathematical principles
involved, and even Faraday supported the wrong views
on this cable design.

The necessary theory contained in the book of Joseph
Fourier, published around 1830. W. Thomson was one
of the few physicists/applied mathematicians who
read and understood this book.

I do not want to include mathematics here,
but a good sorce for the whole story (of the transatlantic
cable design) is the
book of T. Korner on Fourier Analysis.

I lecture on this from time to time to
my students and plan to add this lecture to my
web site sometimes.

Alex.

On Wed, 1 Jun 2005, Lu Abel wrote:

> Gentlemen:
>
> The first cable was plagued with inadequate insulation, resulting in
> frequent bouts of not quite short circuits but signal losses so great
> that telegraphic characters were often simply not received at the far
> end.  It was this that led to it requiring "several hours" to transmit a
> telegram.
>
> "Spreading" of electrical signals takes place when a medium (such as a
> cable) can not transmit the high frequency portion of a signal.  An
> on-off pulse, such as a telegraphic character, theoretically includes
> signal components of very high (indeed, infinite) frequencies.   But the
> speed of transmission is still the speed of light.  Thus a nice sharp
> pulse transmitted on one end of the cable might arrive as a smeared-out,
> possibly unrecognizable mess -- but it would travel across the Atlantic
> (and therefore arrive) in a fraction of a second.
>

   

Reply