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The British government recognised its importance and had given Babbage
th
considerable financial help, a sum roughly equivalent to two early 19 century Royal
Navy frigates. But the industrial revolution had not yet created a precision-metal
industry, so Babbage had to have each cog wheel made by hand. Building a full-scale
version was thus a major challenge.

How did it actually work? Made of bronze and steel, it was about two and a half feet
high, and two feet wide and deep. Essinger explains that Babbage’s basic concept
was to make the teeth on individual cog wheels, called “figure wheels”, stand for

numbers. Rotating vertical rods of independently-moving cog wheels meshed
together to perform the calculations. It had an ingenious carriage mechanism and
worked by a column of helically arranged arms visible at the back which rotated
during every calculation cycle, pulling out the figures needed from the last addition
and incidentally creating a beautiful oscillation, like endlessly changing, rippling
waves (“brain-waves”?) It could produce calculations for mathematical tables, extract
roots and do addition, subtraction, multiplication and division. It was called the

Difference Engine because it repeated regular additions of the differences between
successive items in a mathematical series. This has the advantage of simplifying the
calculation of long and complex mathematical series by basically doing very many
straightforward (but monotonous) additions. A machine doesn’t mind monotony.

The Analytical Engine
Babbage’s second proto-computer, the Analytical Engine, was a different kettle of
fish. It was designed to be the size of a small steam locomotive (think a large modern

van). The biggest problem was again precision parts: it would need as many as
20,000, cog wheels, some again mounted on vertical columns, plus thousands of
gear-shafts, camshafts and power-transmission rods. Calculations done could be
relayed to other parts of the machine.

Babbage made another major innovation. Once again, there was a French

connection. Its operation would be controlled at all stages by punched-card systems,
borrowed from the Jacquard Loom. These were widely used to weave fabrics with
complex patterns. Babbage bought a woven portrait of Jacquard from France, which
fooled the Duke of Wellington into thinking it was an etching; it had taken 24,000
punched cards to produce. Babbage’s card-systems would get the engine ready to
calculate, eliminate the need to set up the cog wheels by hand, and could order it to
follow mathematical laws, thus solving any equation and solving high-level problems.
Here Babbage came his closest to the concept of computer programming.