So true are the principles underlying this method of developing the place-memory, that one deficient in it, providing he will arouse intense interest and will stick to it, may develop the faculty to such an extent that he may almost rival the cat which "always came back," or the dog which "you couldn't lose." The Indians, Arabs, Gypsies and other people of the plain, forest, desert, and mountains, have this faculty so highly developed that it seems almost like an extra sense. It is all this matter of "taking notice" sharpened by continuous need, use and exercise, to a high degree. The mind will respond to the need if the person like the lady, "just _has to_." The laws of Attention and Association will work wonders when actively called into play by Interest or need, followed by exercise and use. There is no magic in the process--just "want to" and "keep at it," that's all. Do you want to hard enough--have you the determination to keep at it? CHAPTER XIV. HOW TO REMEMBER NUMBERS. The faculty of Number--that is the faculty of knowing, recognizing and remembering figures in the abstract and in their relation to each other, differs very materially among different individuals. To some, figures and numbers are apprehended and remembered with ease, while to others they possess no interest, attraction or affinity, and consequently are not apt to be remembered. It is generally admitted by the best authorities that the memorizing of dates, figures, numbers, etc., is the most difficult of any of the phases of memory. But all agree that the faculty may be developed by practice and interest. There have been instances of persons having this faculty of the mind developed to a degree almost incredible; and other instances of persons having started with an aversion to figures and then developing an interest which resulted in their acquiring a remarkable degree of proficiency along these lines. Many of the celebrated mathematicians and astronomers developed wonderful memories for figures. Herschel is said to have been able to remember all the details of intricate calculations in his astronomical computations, even to the figures of the fractions. It is said that he was able to perform the most intricate calculations mentally, without the use of pen or pencil, and then dictated to his assistant the entire details of the process, including the final results. Tycho Brahe, the astronomer, also possessed a similar memory. It is said that he rebelled at being compelled to refer to the printed tables of square roots and cube roots, and set to work to memorize the entire set of tables, which almost incredible task he accomplished in a half day--this required the memorizing of over 75,000 figures, and their relations to each other. Euler the mathematician became blind in his old age, and being unable to refer to his tables, memorized them. It is said that he was able to repeat from recollection the first six powers of all the numbers from one to one hundred.