closely related to the Tablet of the Cross, presents no such septenary arrangement, yet even here there are (counting long and short) seventeen columns, and in the extreme right and left columns just seventeen characters. I find this arrangement by sevens frequently in the Mexican Codices, but in most of these cases it is apparent that this results from the division of 13, as a corresponding arrangement by sixes accompanies, or is to be understood.
Returning to our plate, we may, as I think, make use of this septenary characteristic in determining some of the numerals that are partially obliterated. The red are sufficiently distinct except the missing ones in the upper line, in reference to which there is no question of doubt in the minds of students of this work; and the right-hand one of the line next to the bottom—the only question here being whether this is 18 or 19. Adding together all the numbers indicated by these red numeral characters (including the seven in the upper line), we find the sum to be 153, if we count the right-hand one of the 9th line 18, or 154 if we count it 19. As the latter number (154) is an exact multiple of seven, we conclude that this character is 19, and this agrees with the eroded space and the position of the dots over the remaining portion.
This septenary arrangement does not appear to hold good with the black numerals.
Returning to the first or top line we observe, as before remarked, that it commences with Ymix. According to Landa the Mayas began the computation of their days, that is, their calendar, with one Ymix. We quote his language here, as it is somewhat singular:
"It is curious to note how the dominical letter [of the year] always comes up at the beginning of its year, without mistake or failing, and that none of the other twenty letters appears. They also used this method of counting in order to derive from certain letters a method of counting their epochs and other things, which, though interesting to them, does not concern us much here. It is enough to say that the character or letter with which they begin their computation of the days or their calendar is called one Ymix, which is this 
which has no certain or fixed day on
