In almost all countries, psychologists study the symptoms of extraordinary memory with great interest, especially mathematical memory.

In an interesting book called Mathematiąues et mathe-maticiens, issued in Paris in. 1920", A. Rebiere cites the famous Inaudi as enjoying the greatest fame of this kind. Inaudi was then fifty-something. He willingly underwent numerous experimental screenings. He had a phenomenal memory, and not visual (which is more common), but auditory. During one of the screenings, he introduced a real delight to the audience recruited from the group of professors of the Paris Polytechnic School and the Academy of Sciences. He was very efficient at subtracting two numbers, each of which had po 21 digits (!), these numbers were not written, but only orally mentioned; it was a highly interesting phenomenon, that the result of the action could be given by the experimenter with equal speed in the usual order, ie starting from hundreds of trillions, and vice versa, dictating from unity. Without thinking, he almost marked the day of the week on the date he was given, e.g.. 16 June 862. Inaudi's ability to calculate is complemented by a memory of numbers that is quite astonishing. At the end of one session, he repeated all the numbers from memory, which he operated during that screening, and it was theirs . . . long column.

Way, as Inaudi used to multiply larger numbers, of course by making calculations by heart, will show the following example:

532 • 468
500 • 400 = 200 000
500 • 68 = 34 000
30 • 468 = 14 040
2 • 468 =936
………….248 976

In the first quarter of the 20th century, our compatriot N. Lipowski, who was truly triumphant in England. He solved the most difficult tasks without the slightest mental strain and in the blink of an eye. The well-known English psychologist Spearman observed Lipowski and conducted a series of experiments with him. For example, he gathered several dozen people in his room, he wrote their names on a piece of paper and read them once to Lipowski, who repeated them immediately, and in the reverse order. Lipowski could, just like Inaudi, determine the day of the week for each date given to it, so he did not need a calendar, for he has come to this, that he exchanged the days of the previous year and the next .. . Seconds.

Let's add at the end, that when Lipowski came to London, he couldn't speak a word of English. Within days, he began to speak using words, which in that short time he heard and understood.

The mind of Lipowski - and the phenomenal mnemonics in general - is similar to a photo camera. It keeps everything in it, what will be reflected in it, and retains it for a longer period of time.

As a child, Gauss and Ampere were known for their phenomenal memory of numbers and exceptional skill in calculating. With age, when both great mathematicians plunged into scientific research, their ability to do so began to decline.