Dr. Wallis of Oxford, on one occasion, at night, in bed, proposed to himself a number of fifty-three places, and found its square root to twenty-seven places, and, without writing down numbers at all, dictated the result from memory twenty days afterward. It was not unusual with him to perform arithmetical operations in the dark, as the extraction of roots, e. g., to forty decimal places. The distinguished Euler, blind from early life, had always in his memory a table of the first six powers of all numbers, from one to one hundred. On one occasion two of his pupils, calculating a converging series, on reaching the seventeenth term, found their results differing by one unit at the fiftieth figure, and in order to decide which was correct, Euler went over the whole in his head, and his decision was found afterward to be correct. Pascal forgot nothing of what he had read, or heard, or seen. Menage, at seventy-seven, commemorates, in Latin verses, the favor of the gods, in restoring to him, after partial eclipse, the full powers of memory which had adorned his earlier life.
The instances now given are mentioned by Mr. Stewart but perhaps the most remarkable instance of great memory in modern times, is the case of the celebrated Magliabechi, librarian of the Duke of Tuscany. He would inform any one who consulted him, not only who had directly treated of any particular subject, but who had indirectly touched upon it in treating of other subjects, to the number of perhaps one hundred different authors, giving the name of the author, the name of the book, the words, often the page, where they were to be found, and with the greatest exactness. To test his memory, a gentleman of Florence lent him at one time a manuscript he had prepared for the press, and, some time afterward, went to him with a sorrowful face, and pretended to have lost his manuscript by accident. The poor author seemed inconsolable, and begged Magliabechi to recollect what he could, and write it down. He assured the unfortunate man that he would, and setting about it, wrote out the entire manuscript without missing a word. He had a local memory also, knew where every book stood. One day the Grand Duke sent for him to inquire if he could procure a book which was very scarce. "No, sir," answered Magliabechi; "it is impossible: there is but one in the world; that is in the Grand Seignior's library at Constantinople, and is the seventh book, on the seventh shelf, on the right hand as you go in."
VI. Effects of Disease on the Memory.
Forgetfulness of certain Objects.—Of the effect of certain forms of disease, and also of age, in weakening the power of remembering names, I have already spoken. There are other effects, occasionally produced by disease upon this faculty of the mind, which are not so readily explained. In some cases, a certain class of objects, or the knowledge of certain persons, or of a particular language or some part of a language, as substantives, e. g., seems to be lost to the mind; in other cases, a certain portion of life is obliterated from the recollection. In cases of severe injury to the head, persons have forgotten some particular language; others have been unable to recall afterward the names of the most common objects, while the memory was at no loss for adjectives. A surgeon mentioned by Dr. Abercrombie, so far recovered from a fall as to give special directions respecting his own treatment, yet, for several days, lost all idea of having either a wife or children. The case of Mr. Tennent, who on recovering from apparent death, lost all knowledge of his past life, and was obliged to commence again the study of the alphabet, until after considerable time his knowledge suddenly returned to him, is too well known to require minute description.
Former Objects recalled.—In other instances, precisely the reverse occurs. Disease brings back to mind what has been long forgotten. Thus, persons in extreme sickness, or at the point of death, not unfrequently converse in languages which they have known only in youth. The case cited by Coleridge, and so frequently quoted, of the German servant girl, who in sickness was heard repeating passages of Greek, Latin, and Hebrew, which she had formerly heard her master repeat, as he walked in his study, but of whose meaning she had no idea, is in point in this connection. So also is the case of the Italian mentioned by Dr. Rush, who died in New York, and who, in the beginning of his sickness, spoke English, in the middle of it, French, but on the day of his death, nothing but Italian. A Lutheran clergyman of Philadelphia told Dr. Rush that it was not uncommon for the Germans and Swedes of his congregation, when near death, to speak and pray in their native languages, which some of them had probably not spoken for fifty years. These facts are sufficiently numerous to constitute a class by themselves; they seem to fall under some law of the physical system not yet clearly understood, and are, therefore, in the present state of our knowledge, incapable of explanation.
Inference often drawn from these Facts.—Certain writers have inferred, from the recurrence of things long forgotten, as in the cases now cited, that all knowledge is indestructible and that all which is necessary to the entire reproduction of the past life is the quickened activity of the mental powers an effect which is produced in the delirium of disease. From this they have derived an argument for future retribution Coleridge has made such use of it, and has been followed by Upham, and in part, at least, though with more caution, by Wayland.
The true Inference.—It may be doubted, perhaps, whether the absolute indestructibility of all human knowledge is a legitimate inference from these facts. The most that can with certainty be concluded from them, is, not that all our past thoughts and consciousness must or will return, but that much of it may—perhaps all of it; and this is all we need to know in order to perceive the possibility of a future retribution. It is enough to know, that in the constitution of the mind means exist for recalling, in some way to us mysterious, and under certain conditions not by us fully understood, the objects of our former consciousness, in all the freshness and vividness of their past cognizance, long after they seem to have passed finally from the memory.
Importance of a well-spent Life.—This simple fact, together with the well-known tendency of the mind in advancing age to revert to the scenes and incidents of early life, certainly presents in the clearest light the importance of a well-spent life, of a mind stored with such recollections as shall cast a cheerful radiance over the past, and brighten the uncertain future in those hours of gloom and despondency when the shadows lengthen upon the path of earthly pilgrimage, and life is drawing to a close. If the thoughts and impressions of the passing moment are liable, by some casual association, by some mysterious law of our being, under conditions which may at any moment be fulfilled, to recur at any time to subsequent consciousness, with all the minuteness and power of present reality, it becomes us, as we regard our own highest interests, to guard well the avenues of thought and feeling against the first approach of that which we shall not be pleased to meet again, when it will not be in our power to escape its presence, or avoid its recognition.
VII. Influence of Memory on the Happiness of Life.