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 Fitzwilliam Museum at Cambridge; but I shall not be surprised to find that the system was continued down to George I., or later still. Conservatism is displayed in its perfection in the tenacious adherence of official underlings to established forms and venerable routine. T.S.D. Shooter's Hill, April 8. [Our correspondent will find some curious notices of early dates of Arabic numerals, from the Rev. Edmund Venables, Rev. W. Gunner, and Mr. Ouvry, in the March number of the _Archæological Journal_, p. 75-76.; and the same number also contains, at p. 85., some very interesting remarks by the Rev. Joseph Hunter, illustrative of the subject, and instancing a warrant from Hugh le Despenseer to Bonefez de Peruche and his partners, merchants of a company, to pay forty pounds, dated Feb. 4, 19 Edward II., i.e. 1325, in which the date of the year is expressed in Roman numerals; and on the dorso, written by one of the Italian merchants to whom the warrant was addressed, the date of the payment, Feb. 1325. in Arabic numerals, of which Mr. Hunter exhibited a fac-simile at a meeting of the Institute.] * * * * * _Arabic Numerals._--In the lists of works which treat of Arabic Numerals, the following have not been noticed, although they contain a review of what has been written on their introduction into this part of Europe:--_Archæologia_, vols. x. xiii.; _Bibliotheca Literaria_, Nos. 8. and 10., including Huetiana on this subject; and Morant's _Colchester_, b. iii. p. 28. T.J. * * * * * ERROR IN HALLAM'S HISTORY OF LITERATURE.