By limiting the number of combinations containing the I and J, and the O and Q, which can easily be made interchangeable in the working, and giving but a single reading of most of the devices containing the letters X, Y, Z, which will be the least used, I have been able to present a good working selection of two letters and a repeated letter in I 13 plates. Three digerent letters, as I have stated, can be read in six ways. Take, for instance, the first three letters of the alphabet.