 7 
The other day, at the Institute, Mr Darboux wrote the two numbers:
On the one hand,  4.123.547.238.445.523.831 
and  1.248.126.138.234.129.310 
on the other, and, after having stated the figures, requested that the calculator make the subtraction. Inaudi repeats the problem from memory, because he does not see the written figures behind him.
"Is that right?" said he.
One answers: "Yes."
A smile passes on his lips: "I have the proof", says he, blinking his eyes, and, immediately, announces the correct solution.
Mr. Darboux asks him another question: "What is the number whose cube and square sum to 3,600?". Less than two minutes later, Inaudi answers: "It is the number 15."
After some other tests, covering a plethora of figures, Jacques Inaudi announces to the Academy that he can speak and calculate at the same time and perform two calculations at once. The following test takes place. Mr Poincare proposes to the calculator the following problem: "4,801 divided by the square root of 6". Mr. Bertrand raises, at the same time, the following question: "What day of the week was on 11 March 1822?" Inaudi answers immediately: "11 March 1822 was a Monday. A person born this day would have lived for so many hours, minutes, seconds." (All these figures were recognised as exact.) The result of the operation proposed by Mr Poincare is the number 1,960.
A few days after, in the amphitheatre of the Sorbonne, above Paris, several professors of high standing proposed to him the most complicated operations. He made, with incredible speed, multiplications and divisions
