502 Mr. J. W. L. Glaisher^s Supplementary Remarks 



were so unknown in Holland, that he determined to publish them 

 all in Dutch, " incited thereto by the accomplished Adriaen 

 Vlack, with the promise that he would not spare help nor labour 

 till the completion of the work/^ Decker then explains the ar- 

 rangement of his work, viz. that it is to consist of two parts, of 

 which the first (that under notice) contains the Rahdologia and 

 some developments of his own on commercial arithmetic ; he - 

 then gives a few details about the translation, and some advice 

 about the construction of the instruments required in the Rah- 

 dologia. After this follows a semi- apology for the use of Greek 

 letters in the diagram of the Board in the Local Arithmetic, 

 which he extenuates by pointing out that any other marks would 

 do as well; and the preface concludes with an exhortation to the 

 reader to wait with patience till the Tweede Deel is ready. 

 Decker's own interest-tables are decimal, and Stevinus's tract La 

 Disme is appended in Dutch {De T/iiende^). Apart from the 

 mention of Vlacq and the interest attaching to Decker as one of 

 the first who appreciated the invention of logarithms, his book 

 is of value in reference to the spread of decimal arithmetic. On 

 the whole he seems to have been an intelligent and useful worker, 

 and one who merited more than he has received. 



I may mention that I have examined all the books published 

 on logarithms during the twenty years following the first an- 

 nouncement by Napier in 1614 that are to be found in the li- 

 braries in the British Museum, the Royal Society, the Cambridge 

 University, the Greenwich Observatory, and other institutions, 

 and have thus been enabled to form from inspection a nearly 

 complete bibliography of the works on the subject that appeared 

 during this period. There are only five or six books or editions 

 that I have not yet succeeded in seeing; so that the formation of 

 a perfect bibliography for the time in question will probably be 

 not nearly so difficult a matter as one would a priori suppose. 

 The Oxford libraries ought to be rich in books on the subjectf, 

 as Briggs was Professor there, and the Bodleian possesses most 

 of his manuscripts. There are also several valuable mathema- 

 tical libraries at present under arrangement, which will be pro- 

 bably accessible for research within a reasonable time ; so that 

 the mathematical historian or bibliographer in England will 

 soon be placed in a much improved position with regard to 

 sources of information. 



* Whether this famous tract first appeared in French or Dutch I do not 

 know. De Morgan speaks of a French edition, La Disme, 1585 ; and I 

 have a Dutch edition of the same date {De Thiende, Ley den, 1585) before 

 me as 1 \\rite. 



t On referring to the Catalogue of the Bodleian Library (1843), I find 

 the collection of early logarithmic Tables there is by no means remarkably 

 good. 



