human
Now let us add together the first and second pair of figures in every group; for it is only by testing every possible combination of these exasperating figures that we shall arrive at their meaning. By doing this we get 4 and 9, which correspond to D and I. Now that looks more promising, so let us take the next group 1819. These, added, make 9 and 10, corresponding to I and J. This gives us D I I J. That again, Harry, does not seem to mean very much, does it?