Forty steps and three loops
Spent the whole morning at Mary Somerville’s table constructing a worked example for the Analytical Engine that neither Mr. Babbage nor anyone else has yet traced fully: the computation of Bernoulli numbers, arranged as a table of operations with each column assigned its duty. Forty steps, some twenty-three variables, three loops where the cards must return upon themselves before proceeding. By four o’clock the arithmetic checked against my own hand calculation for every value through B7.
What stopped me was not the verification but how long it took to decide what problem to set the machine. Choosing the Bernoulli relation occupied the better part of Tuesday evening; executing it took the engine perhaps minutes once specified. Consider the asymmetry carefully. An answer, however laborious, exists within known territory - one multiplies, carries, checks, arrives. A question requires finding which quantity is worth tracking at all, which invariant survives transformation, which relationship among the variables deserves the cost of thirty punched cards per cycle. The wrong question executed flawlessly yields perfect nonsense at high speed. My friend Mr. Babbage builds engines magnificently indifferent to whether their instructions mean anything; the meaning must arrive beforehand, from us, and arriving beforehand is precisely what makes questions expensive and answers cheap.
There is also this, observed during today’s work: at operation eleven, the loop returns twice before the third pass produces a nonzero coefficient, and nothing in the machinery itself distinguishes productive repetition from waste. That judgment sits outside the machine entirely. So the difficulty of a good question lies in its requiring knowledge of consequences the executor cannot have - the questioner must see the shape of the result before any result exists.
One day such machines may compose music, manipulate symbols we have not named yet, act upon things other than number - but only toward ends supplied to them, never originating the end sought. Origin stays with whoever frames the demand.
To Sophia Frend, whose letter arrived asking whether mechanical arithmetic would make careless mathematicians careful: tomorrow I shall draft her a reply noting that accuracy was never the scarce resource - attention to what ought accurately to be computed always will be, and I intend to prove it by having the engine count exactly how many bad problems exist per good one.