<s>
The	O
Dumaresq	B-Device
is	O
a	O
mechanical	O
calculating	O
device	O
invented	O
around	O
1902	O
by	O
Lieutenant	O
John	O
Dumaresq	B-Device
of	O
the	O
Royal	O
Navy	O
.	O
</s>
<s>
It	O
is	O
an	O
analogue	O
computer	O
that	O
relates	O
vital	O
variables	O
of	O
the	O
fire	B-Application
control	I-Application
problem	I-Application
to	O
the	O
movement	O
of	O
one	O
's	O
own	O
ship	O
and	O
that	O
of	O
a	O
target	O
ship	O
.	O
</s>
<s>
It	O
was	O
often	O
used	O
with	O
other	O
devices	O
,	O
such	O
as	O
a	O
Vickers	B-Device
range	I-Device
clock	I-Device
,	O
to	O
generate	O
range	O
and	O
deflection	O
data	O
so	O
the	O
gun	O
sights	O
of	O
the	O
ship	O
could	O
be	O
continuously	O
set	O
.	O
</s>
<s>
A	O
number	O
of	O
versions	O
of	O
the	O
Dumaresq	B-Device
were	O
produced	O
of	O
increasing	O
complexity	O
as	O
development	O
proceeded	O
.	O
</s>
<s>
The	O
dumaresq	B-Device
relies	O
on	O
sliding	O
and	O
rotating	O
bars	O
and	O
dials	O
to	O
represent	O
the	O
motion	O
of	O
the	O
two	O
ships	O
.	O
</s>
<s>
Normally	O
the	O
motion	O
of	O
the	O
ship	O
carrying	O
the	O
dumaresq	B-Device
is	O
represented	O
by	O
a	O
metal	O
bar	O
running	O
above	O
the	O
instrument	O
.	O
</s>
<s>
The	O
coordinates	O
can	O
be	O
read	O
to	O
directly	O
provide	O
the	O
"	O
range	O
rate	O
"	O
(	O
the	O
component	O
of	O
motion	O
along	O
the	O
line	O
of	O
bearing	O
)	O
and	O
"	O
dumaresq	B-Device
deflection	O
"	O
(	O
or	O
"	O
speed	O
across	O
"	O
,	O
the	O
component	O
perpendicular	O
to	O
the	O
range	O
rate	O
)	O
.	O
</s>
<s>
Based	O
on	O
the	O
time-of-flight	O
using	O
the	O
instantaneous	O
range	O
between	O
the	O
two	O
ships	O
at	O
the	O
time	O
of	O
firing	O
,	O
these	O
two	O
measurements	O
are	O
added	O
to	O
the	O
initial	O
calculation	O
of	O
the	O
firing	B-Application
solution	I-Application
to	O
produce	O
the	O
corrections	O
for	O
motion	O
.	O
</s>
<s>
Because	O
the	O
dumaresq	B-Device
is	O
an	O
analogue	O
model	O
of	O
the	O
relative	O
motion	O
of	O
the	O
two	O
ships	O
,	O
it	O
does	O
not	O
intrinsically	O
favour	O
which	O
of	O
its	O
settings	O
is	O
an	O
input	O
and	O
which	O
is	O
an	O
output	O
-	O
one	O
can	O
use	O
the	O
center	O
bar	O
to	O
represent	O
the	O
enemy	O
ship	O
motion	O
and	O
the	O
moving	O
portions	O
to	O
represent	O
the	O
dumaresq	B-Device
ship	O
.	O
</s>
<s>
To	O
aid	O
the	O
operation	O
of	O
the	O
system	O
,	O
the	O
dumaresq	B-Device
is	O
normally	O
co-located	O
with	O
instruments	O
showing	O
the	O
direction	O
and	O
speed	O
of	O
the	O
ship	O
,	O
while	O
the	O
operators	O
set	O
the	O
enemy	O
bearing	O
,	O
heading	O
and	O
speed	O
based	O
on	O
calls	O
from	O
the	O
rangetellers	O
.	O
</s>
<s>
In	O
some	O
versions	O
,	O
the	O
rotation	O
of	O
the	O
bar	O
is	O
automated	O
through	O
the	O
use	O
of	O
a	O
gyrocompass	O
and	O
selsyn	B-Algorithm
,	O
in	O
other	O
the	O
speed	O
input	O
was	O
automated	O
using	O
a	O
Forbes	B-Device
Log	I-Device
.	O
</s>
<s>
The	O
design	O
of	O
the	O
dumaresq	B-Device
consists	O
of	O
a	O
circular	O
dial	O
with	O
a	O
cross-bar	O
passing	O
over	O
the	O
centre	O
which	O
is	O
oriented	O
to	O
match	O
the	O
heading	O
of	O
one	O
's	O
own	O
ship	O
.	O
</s>
<s>
The	O
base	O
disc	O
of	O
the	O
Dumaresq	B-Device
features	O
a	O
graph	O
which	O
can	O
be	O
rotated	O
along	O
the	O
line	O
of	O
bearing	O
.	O
</s>
<s>
The	O
mark	O
I	O
Dumaresq	B-Device
was	O
manufactured	O
by	O
Elliott	O
Brothers	O
,	O
who	O
paid	O
for	O
and	O
obtained	O
a	O
patent	O
on	O
the	O
device	O
in	O
the	O
name	O
of	O
its	O
inventor	O
,	O
John	O
Dumaresq	B-Device
,	O
in	O
August	O
1904	O
.	O
</s>
<s>
The	O
mark	O
II	O
Dumaresq	B-Device
was	O
the	O
same	O
as	O
the	O
Mark	O
I	O
,	O
but	O
larger	O
and	O
was	O
in	O
production	O
by	O
Elliotts	O
by	O
1907	O
.	O
</s>
<s>
This	O
model	O
is	O
the	O
zenith	O
in	O
complexity	O
for	O
the	O
dumaresq	B-Device
,	O
and	O
was	O
created	O
for	O
use	O
in	O
the	O
most	O
modern	O
Dreyer	O
tables	O
of	O
WWI	O
,	O
the	O
Mark	O
IV	O
and	O
IV*	O
.	O
</s>
<s>
The	O
electrical	O
dumaresq	B-Device
's	O
special	O
features	O
were	O
very	O
particular	O
to	O
its	O
use	O
in	O
the	O
Dreyer	O
FCTs	O
in	O
which	O
it	O
was	O
fitted	O
,	O
sitting	O
atop	O
a	O
range	B-Device
clock	I-Device
.	O
</s>
<s>
Its	O
new	O
wrinkle	O
was	O
an	O
elaborate	O
electrical	O
device	O
which	O
would	O
,	O
when	O
engaged	O
,	O
continuously	O
and	O
automatically	O
apply	O
the	O
indicated	O
range	O
rate	O
to	O
its	O
range	B-Device
clock	I-Device
and	O
convert	O
the	O
indicated	O
speed-across	O
to	O
a	O
gunnery	O
deflection	O
at	O
the	O
present	O
range	O
.	O
</s>
<s>
These	O
special	O
accoutrements	O
were	O
overtaking	O
the	O
inherent	O
complexity	O
of	O
the	O
dumaresqs	B-Device
themselves	O
.	O
</s>
<s>
This	O
dumaresq	B-Device
(	O
as	O
Admiralty	O
pattern	O
5969A	O
)	O
lasted	O
into	O
service	O
through	O
WWII	O
.	O
</s>
<s>
That	O
this	O
was	O
done	O
by	O
simple	O
thumb	O
work	O
suggests	O
that	O
this	O
dumaresq	B-Device
was	O
meant	O
to	O
operate	O
in	O
the	O
absence	O
of	O
advanced	O
systems	O
such	O
as	O
the	O
Admiralty	B-Device
Fire	I-Device
Control	I-Device
Table	I-Device
that	O
was	O
then	O
in	O
service	O
.	O
</s>
<s>
Before	O
World	O
War	O
I	O
was	O
over	O
,	O
a	O
specialised	O
dumaresq	B-Device
proposed	O
by	O
Captain	O
FC	O
Dreyer	O
was	O
incorporated	O
into	O
the	O
Dreyer	O
Fire	O
Control	O
Table	O
alongside	O
the	O
main	O
one	O
to	O
track	O
and	O
nullify	O
the	O
influence	O
of	O
cross-range	O
winds	O
on	O
the	O
shells	O
as	O
they	O
flew	O
toward	O
the	O
target	O
.	O
</s>
<s>
In	O
the	O
wind	O
dumaresq	B-Device
,	O
the	O
vector	O
bars	O
subtracted	O
own	O
ship	O
's	O
motion	O
from	O
the	O
real	O
wind	O
vector	O
to	O
produce	O
the	O
relative	O
wind	O
vector	O
,	O
which	O
was	O
called	O
"	O
wind	O
you	O
feel	O
"	O
.	O
</s>
<s>
The	O
more	O
sophisticated	O
dumaresqs	B-Device
slowly	O
died	O
out	O
after	O
WWI	O
,	O
their	O
functionality	O
being	O
manifested	O
in	O
other	O
hardware	O
.	O
</s>
<s>
The	O
design	O
of	O
the	O
dumaresq	B-Device
was	O
not	O
well-suited	O
to	O
integration	O
in	O
larger	O
schemes	O
of	O
automated	O
fire	O
control	O
.	O
</s>
<s>
A	O
wind	O
dumaresq	B-Device
,	O
however	O
,	O
can	O
still	O
be	O
found	O
in	O
the	O
transmitting	O
stations	O
of	O
and	O
.	O
</s>
<s>
Simple	O
dumaresqs	B-Device
of	O
almost	O
regressive	O
simplicity	O
continued	O
to	O
be	O
issued	O
through	O
WWII	O
in	O
auxiliaries	O
and	O
transports	O
.	O
</s>
<s>
An	O
example	O
of	O
the	O
Spartan	O
dumaresqs	B-Device
that	O
survived	O
beyond	O
World	O
War	O
I	O
,	O
these	O
were	O
very	O
simple	O
,	O
with	O
fixed	O
cross-bars	O
and	O
an	O
own-speed	O
of	O
12	O
knots	O
that	O
could	O
not	O
be	O
altered	O
.	O
</s>
<s>
The	O
dial	O
plate	O
lacks	O
markings	O
for	O
range	O
rate	O
,	O
implying	O
the	O
fire	O
control	O
staff	O
of	O
the	O
ship	O
would	O
have	O
no	O
range	B-Device
clock	I-Device
at	O
all	O
and	O
that	O
this	O
device	O
was	O
solely	O
to	O
give	O
an	O
idea	O
of	O
what	O
deflection	O
should	O
be	O
used	O
on	O
the	O
gun	O
sights	O
.	O
</s>
<s>
It	O
must	O
have	O
been	O
for	O
convoy	O
vessels	O
with	O
at	O
least	O
a	O
Vickers	B-Device
range	I-Device
clock	I-Device
whose	O
rate	O
could	O
be	O
set	O
according	O
to	O
this	O
indication	O
.	O
</s>
