Edmonton.
{323}
_M. or N._ (Vol. i., p. 415.; Vol. ii., p. 61.).--There have been several
suggestions as to the origin of the use of these letters in the services of
the church, but I do not think that any correspondent has hit upon the very
simple one which I have always considered to be most probably the true
explanation; which is, that as these services were compiled when algebra
stood much higher in the rank of sciences than it does at present, it is by
no means unlikely that these two letters should be used to signify
indefinite and variable _names_, as they are in algebra to represent
indefinite or variable _numbers_, in the same manner as A. B. C. are as
signs of known or definite, and X. Y. Z. of unknown sums.