Modern research has attempted in various ways to find the key to the puzzle of these long and confused series of kings made by the Egyptian priests. Assuming that the names of the kings and the length of their reigns, and the number of reigns belonging to each dynasty, has been handed down correctly by Manetho, but that some of these dynasties were contemporaneous, the attempt has been made to give such a selection from the dynasties of Manetho as would supply a continuous thread for Egyptian history. Thus from the dynasties expressly marked as Memphitic, or Theban, a series may be formed which shortens the calculation of Manetho by at least 1,000 years. We might proceed further in this direction, and reduce Manetho's list by 2,000 or 3,000 years. According to the separate items in the excerpts preserved, Manetho's thirty dynasties include a series of 5,366 Egyptian years (from the year 5702 to the year 340 B.C.); nevertheless, Syncellus, in a passage of his Chronology, has observed that the whole period of history treated by Manetho in his three books covered 3,555 years.[24] This observation has been used to prove that Manetho himself arranged several dynasties contemporaneously; and thus, by taking the whole total of years given by Syncellus as a basis, the year 3892 B.C. has been fixed as the first year of the reign of Menes. No doubt a selection may be made from the dynasties of Manetho in such a way that the sum total of the reigns included in it will carry us no farther back than this year.[25] But it is clear from the accounts of Herodotus and Diodorus that the series of kings made by the Egyptian priests were strictly successive; and this fact is abundantly confirmed by the Turin papyrus and the excerpts preserved from Manetho himself. The 3,555 years which Syncellus brings forward cannot, in the face of his own excerpt, be taken as a number really derived from Manetho, and with this number all the calculations founded upon it fall to the ground.[26]