48. Rock, cork.
49. Place, lace, ace, lac.
50. a, e, i, o, u, y.
51. The solution of the enigma which begins:—
“Twice six is six, and so
Six is but three;
Three is just five you know,
What can we be?”
is the number of letters of the alphabet used in spelling a number. Thus twice six, or twelve, is composed of six letters, and so on.