January 15, 1803 Dunbar wrote to Jefferson: "Bad health which has endured above twelve months has withheld much of my attention from Philosophic objects, a favorable change having lately taken place, I perceive with satisfaction that my mind and body are both recovering their former tone and now again enjoy the pleasing prospect of dedicating my leisure hours to my favorite amusements." Dunbar's next contribution to the Transactions was entitled, "Abstract of a communication from Mr. Martin Durale, relative to fossil bones, etc., of the County of Opelousas, west of the Mississippi to Mr. William Dunbar of the Natchez," etc. In this account Dunbar, in referring to certain phenomena makes use of the following expression, which has characterized the true philosophers of all ages, "I have never observed them without endeavoring to ascertain the cause of them." This communication was accompanied by "pretty full vocabularies of the tongues of two Indian nations of that country," to which "was added a sketch of the religion or superstition of these people." In this connection, Dunbar says, "From several other quarters I have used some efforts to draw similar information, but am hitherto disappointed." He also makes mention of a letter which he had just received from Sir Joseph Banks with an extract from the Transactions of the Royal Society. January 28, 1804, Dunbar wrote to Jefferson transmitting his seventh and eighth contributions to Volume Six of the Transactions, while an extract from his letter was published as a ninth contribution. His seventh article was entitled a "Description of the river Mississippi and its Delta, with that of the adjacent parts of Louisiana." In this he gives a table of the mean altitude of the waters of the Mississippi at Natchez, from the lowest ebb to the highest elevation for the first and fifteenth of each month in the year. It also contains a good account of overflows and some philosophical reflections on the velocity, banks, currents, deposits and depth of the river and the effects of confining it to its channel. In speaking of the overflow lands he says, "although no successful attempt is likely to be made in our day, yet posterity will reclaim" them. He discusses the methods used in Holland and in Egypt, and makes several speculations as to the method that will probably be successful. This sketch, he says, in conclusion, "is the result of occasional observation for a series of years and of scattered information collected from various sources, probably often uncertain, from a cause which is unfortunately, too general; viz: the extreme inattention of persons, even of some education to the most curious phenomena passing daily under their review." The eighth article was entitled: "Monthly and Annual Results of Meteorological Observations" for the years 1801, 1802, 1803.