This text was not written by Mendeleev, but is a biographical account of his discovery of the periodic table reconstructed from testimony and archived personal documents by B. M. Kedrov, and published in the Soviet Review, 8:2, 26-45, in 1967. I have lifted the most relevant exerpts, and encourage you to read the whole paper.

INTRO

In every scientific discovery, we can distinguish at least two aspects: first, the precise course of the discovery with all details and in all its individuaiity; second, its final result, absimple chance. Such moments, for example, are frequently identified as occurrences of certain sorts of associations that presumably led to the discovery stracted from all circumstances and subjective considerations connected with the personal characteristics of the discoverer and the circumstances under which the discovery was made. In this “purified view” the substance of the discovery usually enters into science and establishes itself there in the quality of ascertained truth. Because of this, in the great majority of cases, the history of science does not present information about the specific path that a particular discovery followed; but even if it preserves this information, it is usually only in the form of anecdotes that have come down to us, or fragments about some one moment of the whole discovery, which possibly did not play a decisive role, but was preserved thanks to simple chance.

Such moments, for example, are frequently identified as occurrences of certain sorts of associations that presumably led to the discovery or invention, (The observation by John Watt of the jumping lid of a tea kettle that, according to tradition, gave him the idea of using the force of steam in the steam engine.) Sometimes the association is based on a direct analogy arising suddenly in the consciousness of the discoverer. (The observation by Kekule, from the upper deck of a London omnibus, of the crowds of people scurrying in the streets suggested to his mind, according to his testimony, the similar model of the movement and interaction among the atoms.) Or such moments can be identified when noticing particular phenomena that give rise to hypotheses about their cause. (A falling apple suggesting to a lad Isaac Newton the idea of universal gravitation.) And so forth.

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WILLPOWER, TIME RESTRICTION, AND FAVORABLE CIRCUMSTANCE

Thanks to these purely accidental coincidences, on the 17th of February, unexpectedly for Mendeleev, both lines of his activity during this period came in conflict and crossed: first, writing the Fundamentals of Chemistry and, second, his trip to the dairy co-op. Since his trip was agreed upon with the interested organizations, Mendeleev could not avoid his obligation to go on a specific day. This circumstance strictly limited the time he could set aside for solving the problem confronting him relating to the arrangement of the next materials in the Fundamentals of Chemistry. In other words, Mendeleev achieved the discovery of the periodic law under conditions of the most severe Zeitnöt [time pressure], which gave rise to a very distinctive character and path in its development. The general psychological situation of Mendeleev on the day of the discovery can be compared with the situation of a chess master, caught at the very beginning of a game in Zeitnöt, but striving at all costs to achieve a victory in spite of the unfavorable conditions. Mendeleev achieved this victory thanks to the very great force of his will, subordinating all his activity to a unified contribution to his goal, rapidly choosing suitable as well as correct methods for achieving the whole, with maximum economy of time and force. The condition of Zeitnöt eliminated the possibility of exploring and testing various paths, and did not permit time for a comprehensive, leisurely deliberation about all questions, for postponing them to the following day in order to return to their solution once again.

If a man’s willpower plays a large role in all creative acts, which are conscious and goal-oriented, then in this case, where the creative process took its course under conditions of Zeitnöt, the role and influence of willpower on the whole course of the discovery, on its tempo and direction, and even on its very outcome, must necessarily have been greatly magnified. Without this, Mendeleev could not, in the course of a single day (February 17, 1869) have accomplished such a gigantic task, which under other circumstances would have required a minimum of several days or, possibly, even several weeks. It is sufficient to say that for writing an account of the discovery which was made on the 17th of February (in the form of an article) he needed at least ten days.

It goes without saying that willpower alone, however large a role it played, still could not make possible the solution of the problem. Without arousing all his creative forces and talents, without focussing on the solution of one single question, Mendeleev would not have been able to so quickly achieve such a remarkable result. The archive materials that have been discovered permit us to recreate reasonably precisely this moment when the very discovery itself began, and when, as we can suppose, the creative inspiration came to Mendeleev.

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DILIGENT SEARCH

The work of attention, work of a strictly selective character, permitted Mendeleev, even in the first steps of the scientific discovery, to detect the existence of a definite regularity [between the elements]. Later, after more than thirty years, he recalled: “To search for something - though it be mushrooms or some pattern is impossible, unless you look and try”.

Comparing the discovery of a new law of nature with a search for mushrooms has deep psychological significance. A person, wanting mushrooms, attends with concentration on detecting among many different objects (dry leaves, roots of trees, brushwood, stalks of grass, moss, and so on) the very definite signs that are peculiar to mushrooms. The task, from a psychological standpoint, consists in not passing by these signs, not losing them among other more striking signs, whose detection in this case turns aside the attention of the collector of mushrooms, Just such a task, in essence, stood before Mendeleev in working out the system of the elements: he must detect the regular sequence in the order of groups of elements according to the atomic weights of their members. But for this it was necessary to find and single out, from among the numerous relations among elements including the relation among their atomic weights that which would provide a unified arrangement of the groups of elements in a definite order. Toward this relation the notion of the differences in atomic weights of adjoining groups Mendeleev turned his attention, extracting it from his general consideration of all the relations among elements and underlining it, as it were, in his memory.

The successful beginning of the research could only stimulate its author to further search for the already sensed lawfulness; while the early success ought to inspire and, accordingly, increase the intensity of all the creative forces of the scientist.

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A MASTER OF HIS FIELD

The above first step in the discovery of the periodic law cannot be understood without taking account of the previous prolonged work of Mendeleev, which served as a preparation for this discovery. This preparatory work had continued for nearly 15 years and extended in all directions.

In the course of this long period, Mendeleev mastered the interactions and relations of the elements and their compounds from every standpoint (resemblances of crystal form, or isomorphism; relations of specific weights and atomic volumes; regularities in all compounds, particularly higher oxides of salts, in correspondence with their theoretical limits; relations among the atomic weights of chemically similar elements belonging to one natural group).

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ALL FORMED IN HIS HEAD

In all likelihood, under these circumstances the rush of ideas of Mendeleev gave place to a tense one could say, agonizing process, searching for the required means that would permit a maximal economy of time and effort, leading to completion of the whole work and not interrupting it halfway. Calling on Mendeleev, it would seem, at just this moment, his friend A. A. Inostrantzev found Mendeleev in a gloomy, depressed state. According to Inostrantzev, Mendeleev began to speak of what was subsequently the embodiment of the periodic system of elements, But at this moment the law was still not formulated and the table still not completed. “It’s all formed in my head,” said Mendeleev with bitterness, “but I can’t express it in the table.”

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VISUALIZATION

Sometime later Mendeleev wrote that through his study of compounds he involuntarily acquired the idea that between masses (atomic weights) and the chemical elements (their specific properties) there must necessarily be some relation, and one should therefore search for functional relations between them. ‘Here I began to sort out, writing down the elements on separate [playing] cards with their atomic weights and fundamental properties, comparing elements that were similar in atomic weight, and quickly came to the conclusion that the properties of elements stand in periodic relation to their atomic weights. . .”.

From these words it is clear that “sorting out” the cards with the elements written on them was similar to sorting out cards according to suit “similar elements” and denomination “similar atomic weight” (compare the schema below).

In connection with the second stage of the discovery, we can illustrate the role of such psychological phenomena as derive from imagination and memory.

When Mendeleev turned to the cards of elements, the very analogy with patience [the card game which Americans call solitaire], which probably came to him directly or indirectly at this moment, ought to have brought into his mind the complete chart of the arrangement of the elements (of course along very general lines, in the form of its rough outline). This outline might organize itself, for example, if only in conceiving that all the elements should be arranged according to family likeness, in groups, in horizontal rows, and also by groups, according to atomic weight, in the vertical columns. It goes without saying that the specific details, for example, the location of this or that poorly known element in some particular spot, could not be determined immediately, but would requid a thorough examination, with a study of all the properties and relations of the given element with other elements. However, the general character of the future, and already developing, system of elements would undoubtedly stand out in Mendeleev’s consciousness, so that he could visualize already sufficiently clearly the above-mentioned two incomplete tables which he had written down on paper.

Laying out cards in patience presupposes that the player knows beforehand, and holds in mind, the requirements of the game for the order of disposing of the cards, although actually the cards are disposed in a very different order before his eyes, that is to say, randomly and chaotically. Having in his mind’s eye the required arrangement, that is, having recourse to the working of his imagination, the player begins to rearrange the cards so that, gradually and step by step, he brings them to the arrangement which is required by the rules of the game and which he, during this whole time, holds in his mind.

Strictly speaking, this is the path Mendeleev took, although the image of the correctly arranged cards of elements could not stand before him as clearly and definitely as before the player of patience. Nevertheless, since the conditions of “chemical patience” were already defined (grouping the elements according to properties in rows and according to similarity of atomic weight in columns), the idea could grow into a general picture of the future system of elements in its completeness. But this shows that imagination ought to have played, and did play, apparently in the case of Mendeleev, a significant role in the decisive stage of the discovery of the periodic law.

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MENDELEEV'S DREAM

On the evening of the day of the discovery, when the rough table shown in Fig. 1 was complete, that is, when he had finished his game of patience with the cards of elements, there occurred a remarkably interesting and psychologically highly significant event. Inostrantzev has recounted it. According to his words, for three days and three nights Mendeleev did not lie down to sleep, but worked at his desk, trying to combine the results of his mental constructions in the table, but his attempts to achieve this seemed unsuccessful. Finally, suffering from extreme fatigue, he lay down to sleep and immediately slept deeply. Concerning what happened next, he several times reported to Inostrantzev: “I saw in a dream a table where all the elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper only in one place did a correction later seem necessary.” ...

Finding the archive materials not only confirmed this earlier conjecture, but allowed a test of the accuracy of Inostrantzev’s account. The dates available on these materials show that the whole discovery, as finally put together and circulated in print in the “Tentative System of Elements,” was achieved in just one day February 17, 1869. Therefore, the account of three sleepless nights appears grossly exaggerated. Hence, it is necessary to clarify what Mendeleev had in mind when he said that “the elements fell into place as required.” But for this it is necessary at the outset to determine what table he was speaking about. In any case it could not be the notes that are reproduced in Fig. 1, for there are numerous corrections in these, while according to Inostrantzev, in the table of Mendeleev’s dream, ‘only in one place did a correction later seem necessary,” This condition is satisfied by the fair copy of the notes that was sent to the printer. On this there was actually just one correction made later. But if this is so, then comparing both tables the notes (see Fig. 1) with the copy sent to the printer will permit us to decide definitely what the phrase “falling in place as required” means. ...

We can suppose that, having finished laying out the game of patience and feeling keenly the need for rest, Mendeleev deferred deciding the question of the form of presentation of the system he had constructed, and lay down to rest with the idea of considering this, but still not having eliminated the defects. In this case he could actually have dreamt of a table in which “the elements fell into place as required,” that is, in columns reading downward according to increasing rather than decreasing atomic weight. Awakening, he wrote down what he had seen in the dream. This was the fair copy of the table, which he sent to the typesetter.

Pondering this example allows us to draw two inferences about the way the discovery proceeded: first, the creative thoughts of Mendeleev even in his dream could continue his activity in the direction previously pursued, leading to the completion and improvement of the representation he had found earlier. Second, one can surely not speak of the discovery of the periodic law during sleep, although the testimony of Inostrantzev would give grounds for such a conclusion if we accepted it completely on faith and did not subject it to critical examination on the basis of the newly discovered archive materials. Several authors have made this error. As a matter of fact one can affirm, with respect to the more general formulation of the discovery, that it was by no means accomplished by the scientist in his sleep, but in a fully awakened condition.

NOTE: Kedrov here partially denies the credit due to Mendeleev's dream in this discovery. Clearly this is to repudiate the instincts of common people who would conclude that this discovery came from a 'dream world' or by magic, and was not the result of years of rigorous, willful study. One should not take this as Kedrov ignoring the contribution of the dream state: he instead conceives of conscious thoughts operating independently while the mind sleeps. We can also see Soviet political pressure here, as later he quotes Lenin, saying 'Not psychology, not phenomenological spirit, but logic determines the truth'. ...

DISCOVERY ATTAINED THROUGH INCREMENTAL STEPS

Describing the creative process that led Mendeleev to the discovery of the periodic law allows us to draw several conclusions about this particular discovery, and about scientific creativity in general. First of all, attention should be called once more to the uninterrupted activity of the will, which during the whole of February 17, 1869 held all the forces and capabilities of the scientist in a condition of highest alertness, and permitted the discovery to be attained in the furthest measure and with all aspects of it that could be handled with the facts available at that time. By it the sort of "pulsations" of Mendeleev’s creative efforts were governed, expressed in an alternate rise and fall of creative energy, with a subsequent still higher rise and new fall, or, better stated, a psychological discharge to finish all the work, changing to a slump, in the course of which the creative activity did not halt completely, but continued developing in the previous direction.

Investigation of the entire process of discovery shows that there was nothing in it that would argue for complete suddenness and unexpectedness of its origins, any incoherence in its course, or the presence of any inexplicable “leaps,” surprises or “revelations from Heaven.” On the contrary, the newly discovered material allows us to establish this process as a fully connected, strictly ordered growth of the ideas of the scientist, though accomplishing very quickly, in the course of a day, a very important work that under other conditions would have taken very much more time.

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AVOIDING EXXAGERATION AND LEGEND

In conclusion we touch on the question of how sometimes there arise afterwards various hypotheses and legends about how a discovery was made, not corresponding to the actual history. Earlier, the account of Inostrantzev was mentioned, according to which Mendeleev revealed that he had discovered the periodic system in his sleep! Checking this account, which came to us from the testimony of an eyewitness, showed that much in Inostrantzev’s account was exaggerated - more than that, distorted and confused.

Partly the sources of legends about scientific discoveries arise out of attempts to extrapolate a simple after-the-fact logical interpretation of the accomplished discovery, in other words, by explaining the results of the discovery to represent them as the route of the discovery itself. From a psychological standpoint this is as though the conclusion and the premises exchanged places, and the premises were subsequently entirely forgotten.