<s>
The	O
differential	B-Device
analyser	I-Device
is	O
a	O
mechanical	O
analogue	O
computer	O
designed	O
to	O
solve	O
differential	O
equations	O
by	O
integration	O
,	O
using	O
wheel-and-disc	O
mechanisms	O
to	O
perform	O
the	O
integration	O
.	O
</s>
<s>
Though	O
Thomson	O
called	O
his	O
device	O
an	O
"	O
integrating	O
machine	O
"	O
,	O
it	O
is	O
his	O
description	O
of	O
the	O
device	O
,	O
together	O
with	O
the	O
additional	O
publication	O
in	O
1876	O
of	O
two	O
further	O
descriptions	O
by	O
his	O
younger	O
brother	O
,	O
Lord	O
Kelvin	O
,	O
which	O
represents	O
the	O
invention	O
of	O
the	O
differential	B-Device
analyser	I-Device
.	O
</s>
<s>
On	O
Lord	O
Kelvin	O
's	O
advice	O
,	O
Thomson	O
's	O
integrating	O
machine	O
was	O
later	O
incorporated	O
into	O
a	O
fire-control	B-Application
system	I-Application
for	O
naval	O
gunnery	O
being	O
developed	O
by	O
Arthur	B-Application
Pollen	I-Application
,	O
resulting	O
in	O
an	O
electrically	O
driven	O
,	O
mechanical	O
analogue	O
computer	O
,	O
which	O
was	O
completed	O
by	O
about	O
1912	O
.	O
</s>
<s>
However	O
,	O
the	O
first	O
widely	O
practical	O
general-purpose	O
differential	B-Device
analyser	I-Device
was	O
constructed	O
by	O
Harold	O
Locke	O
Hazen	O
and	O
Vannevar	O
Bush	O
at	O
MIT	O
,	O
1928	O
–	O
1931	O
,	O
comprising	O
six	O
mechanical	O
integrators	O
.	O
</s>
<s>
When	O
he	O
published	O
a	O
further	O
article	O
on	O
the	O
device	O
in	O
1931	O
,	O
he	O
called	O
it	O
a	O
"	O
differential	B-Device
analyzer	I-Device
"	O
.	O
</s>
<s>
According	O
to	O
his	O
1970	O
autobiography	O
,	O
Bush	O
was	O
"	O
unaware	O
of	O
Kelvin	O
’s	O
work	O
until	O
after	O
the	O
first	O
differential	B-Device
analyzer	I-Device
was	O
operational.	O
"	O
</s>
<s>
Claude	O
Shannon	O
was	O
hired	O
as	O
a	O
research	O
assistant	O
in	O
1936	O
to	O
run	O
the	O
differential	B-Device
analyzer	I-Device
in	O
Bush	O
's	O
lab	O
.	O
</s>
<s>
In	O
Norway	O
,	O
the	O
locally	O
built	O
Oslo	B-Device
Analyser	I-Device
was	O
finished	O
during	O
1938	O
,	O
based	O
on	O
the	O
same	O
principles	O
as	O
the	O
MIT	O
machine	O
.	O
</s>
<s>
In	O
the	O
United	O
States	O
,	O
further	O
differential	B-Device
analysers	I-Device
were	O
built	O
at	O
the	O
Ballistic	O
Research	O
Laboratory	O
in	O
Maryland	O
and	O
in	O
the	O
basement	O
of	O
the	O
Moore	O
School	O
of	O
Electrical	O
Engineering	O
at	O
the	O
University	O
of	O
Pennsylvania	O
during	O
the	O
early	O
1940s	O
.	O
</s>
<s>
The	O
latter	O
was	O
used	O
extensively	O
in	O
the	O
computation	O
of	O
artillery	B-Application
firing	O
tables	O
prior	O
to	O
the	O
invention	O
of	O
the	O
ENIAC	B-Device
,	O
which	O
,	O
in	O
many	O
ways	O
,	O
was	O
modelled	O
on	O
the	O
differential	B-Device
analyser	I-Device
.	O
</s>
<s>
In	O
1947	O
,	O
UCLA	O
installed	O
a	O
differential	B-Device
analyser	I-Device
built	O
for	O
them	O
by	O
General	O
Electric	O
at	O
a	O
cost	O
of	O
$	O
125,000	O
.	O
</s>
<s>
The	O
UCLA	B-Device
differential	I-Device
analyzer	I-Device
appeared	O
in	O
1951	O
's	O
When	O
Worlds	O
Collide	O
,	O
where	O
it	O
was	O
called	O
"	O
DA	O
"	O
.	O
</s>
<s>
a	O
complete	O
differential	B-Device
analyser	I-Device
machine	O
was	O
developed	O
(	O
illustrated	O
)	O
to	O
calculate	O
the	O
movement	O
of	O
an	O
object	O
and	O
other	O
problems	O
with	O
mechanical	O
components	O
,	O
and	O
then	O
draws	O
graphs	O
on	O
paper	O
with	O
a	O
pen	O
.	O
</s>
<s>
Restored	O
in	O
2014	O
is	O
one	O
of	O
only	O
two	O
still	O
operational	O
differential	B-Device
analyzers	I-Device
produced	O
before	O
the	O
end	O
of	O
World	O
War	O
II	O
.	O
</s>
<s>
In	O
Canada	O
,	O
a	O
differential	B-Device
analyser	I-Device
was	O
constructed	O
at	O
the	O
University	O
of	O
Toronto	O
in	O
1948	O
by	O
Beatrice	O
Helen	O
Worsley	O
,	O
but	O
it	O
appears	O
to	O
have	O
had	O
little	O
or	O
no	O
use	O
.	O
</s>
<s>
A	O
differential	B-Device
analyser	I-Device
may	O
have	O
been	O
used	O
in	O
the	O
development	O
of	O
the	O
bouncing	O
bomb	O
,	O
used	O
to	O
attack	O
German	O
hydroelectric	O
dams	O
during	O
World	O
War	O
II	O
.	O
</s>
<s>
Differential	B-Device
analysers	I-Device
have	O
also	O
been	O
used	O
in	O
the	O
calculation	O
of	O
soil	O
erosion	O
by	O
river	O
control	O
authorities	O
.	O
</s>
<s>
The	O
differential	B-Device
analyser	I-Device
was	O
eventually	O
rendered	O
obsolete	O
by	O
electronic	O
analogue	O
computers	O
and	O
,	O
later	O
,	O
digital	O
computers	O
.	O
</s>
<s>
The	O
model	O
differential	B-Device
analyser	I-Device
built	O
at	O
Manchester	O
University	O
in	O
1934	O
by	O
Douglas	O
Hartree	O
and	O
Arthur	O
Porter	O
made	O
extensive	O
use	O
of	O
Meccano	O
parts	O
:	O
this	O
meant	O
that	O
the	O
machine	O
was	O
less	O
costly	O
to	O
build	O
,	O
and	O
it	O
proved	O
"	O
accurate	O
enough	O
for	O
the	O
solution	O
of	O
many	O
scientific	O
problems	O
"	O
.	O
</s>
<s>
It	O
is	O
estimated	O
that	O
"	O
about	O
15	O
Meccano	O
model	O
Differential	B-Device
Analysers	I-Device
were	O
built	O
for	O
serious	O
work	O
by	O
scientists	O
and	O
researchers	O
around	O
the	O
world	O
"	O
.	O
</s>
