principal questions were brought in a definite form before the
contributors to the "NOTES AND QUERIES," I feel quite sure that a not
inconsiderable number of them will be able to contribute each his
portion to the solution of what may till now be considered as almost a
mystery. With your permission, I will propose a few queries relating to
the subject,

1. When did the abacus, or the "tabel" referred to in my former letters,
cease to be used as calculating instruments?

The last printed work in which the _abacal_ practice was given for the
purposes of tuition that I have been able to discover, is a 12mo.
edition, by Andrew Mellis, of Dee's _Robert Recorde_, 1682.

2. When did the method of _recording results_ in Roman numerals cease to
be used in mercantile account-books? Do any ledgers or other
account-books, of ancient dates, exist in the archives of the City
Companies, or in the office of the City Chamberlain? If there do, these
would go far towards settling the question.

3. When in the public offices of the Government? It is probable that
criteria will be found in many of them, which are inaccessible to the
public generally.

4. When in the household-books of royalty and nobility? This is a class
of MSS. to which I have paid next to no attention; and, possibly, had
the query been in my mind through life, many fragments {435} tending
towards the solution that have passed me unnoticed would have saved me
from the necessity of troubling your correspondents. The latest that I
remember to have particularly noticed is that of Charles I. in the