Suppose the day counted from is 11 Muluc of the eleventh month, and the number of days to be counted (or the interval) is 19; by adding together the numbers and casting out the thirteens the following result is obtained: 11 + 19 - 13 - 13 = 4. Counting forward on the table 19 days from 11 Muluc (the sixth number in the eleventh figure column), we reach 4 Lamat (the fourth day of the twelfth month). When the sum of the numbers is a multiple of 13 the number obtained is 13, as there can be no blanks, that is to say, no day without a number. As the plates of the codices are usually divided into two or three compartments by transverse lines, it is necessary to adopt some method of referring to these in order to avoid the constant repetition of "upper," "middle," and "lower" division. On the plan proposed by Dr. Förstemann, in his late work on the Dresden Codex (Erläuterungen zur Mayahandschrift der Königlichen öffentlichen Bibliothek zu Dresden), these divisions are designated by the letters _a_, _b_, and _c_; this plan will be adopted in this paper. The letter _a_ joined to the number of a plate, therefore, will signify that the division referred to is the upper one, as Plate 12_a_; the letter _b_ signifies the middle one where there are three divisions or the lower one where there are but two; and the letter _c_ signifies the lowest or bottom division where there are three. Where reference is made to the fac simile of the Dresden Codex, Kingsborough's colored edition is always to be understood, except where another is specially mentioned. Running through Plates 36_c_ and 37_c_ is a continuous line of day symbols and red and black numeral characters as follows, the numbers and names below the characters being explanatory and of course not on the original: [Illustration: FIG. 359. Lines of day and numeral symbols. Pl. 36 10 XI Men | 15 XII Oc | 9 IX Cauac Pl. 37 11 VII Oc | 20 I Oc | 10 XI Ahau] As colors are not used in these figures the red numerals are indi cated[TN-2] by hollow or outline dots and lines and the black numerals by solid lines and dots.[272-1] In order further to assist those unacquainted with the symbols the same line is here given in another form, in which the names of the days are substituted for the symbols, Roman numerals for the red numbers, and Arabic for the black: 10, XI Men; 15, XIII Oc; 9, IX Cauac; 11, VII Oc; S, I Oc; 10, XI Ahau. The S is introduced to represent a numeral symbol different from the lines and dots and will be explained when reached in the course of the illustration.