I desired her to tell her boy when he grew up that, when an infant, the Duke of Wellington had played with him. I then returned and told the Duke the object of my mission. His approbation was indicated by a happy smile.
One morning the Duke of Wellington called in Dorset Street with the late Countess of Wilton, to whom he wished me to show the Difference Engine. Its home was at that period in my drawing-room. We sat round it whilst I explained its mode of action, and made it calculate some small Table of numbers.
When I had concluded my explanation. Lady Wilton, addressing me, said, "Now, Mr. Babbage, can you tell me what was your greatest difficulty in contriving this machine?" I had never previously asked myself that question; but I knew the nature of it well.
It arose not from the difficulty of contriving mechanism to execute each individual movement, for I had contrived very many different modes of executing each: but it really arose from the almost innumerable combinations amongst all these contrivances—a number so vast, that no human mind could examine them all.
It instantly occurred to me that a similar difficulty must present itself to a general commanding a vast army, when about to engage in a conflict with another army of equal or of greater amount. I therefore thought it must have been felt by the Duke of Wellington, and I determined to make a kind of psychological experiment upon him.
Carefully abstaining from any military term, I commenced my explanation to Lady Wilton. I soon perceived by his countenance that the Duke was already in imagination again in Spain. I then went on boldly with the explanation of my
