303 Mr. J. W. L. Glaisher on some new Facts in 



that rendered the latter's work nugatory, and has led to the per- 

 manent retention of the bad old system. Tables in \vhich the 

 division of the right angle is entirely centesimal have been pub- 

 lished by Hobert and Ideler, Borda and Delambre, &c. ; and 

 such are to be found in Callet ; but the system has apparently 

 become too fixed to render a change possible or, perhaps, desirable 

 now. 



In conclusion, I may express a request that if any reader of 

 this should come across any information of a special character 

 with regard to Vlacq or the early history of logarithms, he 

 will be kind enough to favour me with the reference to the 

 place where it occurs. 



Trinity CoUepje, Cambridge, 

 September 15, 18/2. 



Postscript. — After writing the above notice, it occurred to me 

 that if there was another copy of Decker anywhere, it would 

 probably be in the Graves library at University College, London. 

 This library (containing about 10,000 volumes), which was 

 formed by the late Professor Graves, of Cheltenham, is perhaps 

 the finest collection of old mathematical books in the country^ 

 and is most likely the best ever collected by an individual. The 

 books are at present only partially arranged; so that, although 

 there is a catalogue, there are no press marks. It is therefore 

 possible to know what works there are in the library, but not 

 where to find them. The catalogue contains two books by 

 Ezechiel de Decker, viz. the Nieuwe Telkonst above noticed, 

 and another work of the same date (1626). I was kindly per- 

 mitted to search for these works, and, with the assistance of 

 the librarian, had the good fortune to find the latter. Its 

 title is "Eerste Deel vande Nieuwe Telkonst, inhoudende 

 verscheyde manieren van Kekenen eerst ghevonden van loanne 

 Nepero Heer van Alerchistoun, ende uyt het Latijn overgheset 

 door xidrianum Vlack .... door Ezechiel de Decker .... Noch 

 is hier achter byghevoeght de Thiende van Symon Stevin van 

 Brugghe. Ter Goude, By Pieter Rammaseyn .... 1626 ; " and 

 it forms a quarto volume of perhaps 450 pages. The contents 

 are : — a complete translation of Napier^s Rabdologia of 1617, 

 which occupies pp. 1-148 ; then Ezechiel de Decker van Coop- 

 mans JRekeninghen, which extends to page 308, and is followed 

 by more than a hundred pages of tables of wages, money, 

 interest, &c. ; and, at the end, a translation of Stevinus's cele- 

 brated tract La Disme (27 pages). The preface is dated Wt 

 Goude den 4 September int Yaer 1626, the same day as that on 

 which the preface to the octavo work Vvas written. It will be 

 noticed that Vlacq^s name occurs on the titlepage ; and there 



