on some early Logarithmic Tables, 501 



There is, however, a copy in the British Museum, acquired in 

 1854; and as it bears the name of H. C. Schumacher, Copenhagen, 

 1816, it no doubt belonged to the celebrated astronomer. The 

 preface is not dated; and there is no "privilege^' or date* of com- 

 pletion of printing (or perhaps the last page is torn out) ; so that 

 there exists no means of deciding whether the priority of pub- 

 lication belongs to Decker or Henrion. It struck me as not 

 unlikely that there really was perhaps no ''privilege,'^ as the 

 " privilege " to Henrion's Cosmographie , 2nd edit., Paris, 1626, 

 includes '^Uoutes ses oeuvres,^^ and is dated Sept. 7, 1624, the 

 "acheve d^imprimer^^ being April 1626; but the L' Usage du 

 Mecrometre, 1630, by the same author, has the "privilege^' as 

 usual. In the preface to his Traicte des Logarithmes Henrion 

 makes no reference to Wingate's publication at Paris the pre- 

 vious year ; he states that he had calculated some logarithms 

 himself when the appearance of Briggs^s Arithmetica rendered 

 the further progress of his work unnecessary. Lalande men- 

 tions five books of Henrion; and I have met with three or four 

 others ; so that he must have been a somewhat prolific mathe- 

 matical writer for the time : he describes himself on his title- 

 pages as *' deraeursnt en I'isle du Palais." 



Of Decker's Eerste Deal vande Nieuwe Telkonst 1 have found 

 another copy in the library of Trinity College, Cambridge, and 

 have therefore been enabled to examine it at leisure. In the 

 preface Decker remarks that, when he was professor of geometry 

 and arithmetic, he noticed the great fear and dislike evinced 

 towards the arts that involved long calculations, and, being very 

 anxious to find a remedy for this, he carefully studied every new 

 mathematical work on its appearance, and amongst others Na- 

 pier's Canonis Logarithmorum Mirifici Descriptio. This book 

 (which Vlacq translated for him, as he was ignorant of Latin) 

 pleased him exceedingly; but he saw that it was unsuitable for 

 the general public. Soon after, Vlacq called his attention to and 

 translated for himl^ apiev'^Rabdologia fjwhich. completely realized 

 his desires. The announcement contained in it about the other 

 method of logarithms (viz. the adoption of the decimal base) led 

 him to procure from England Briggs's Arithmetica and Gunter's 

 Table of sines and tangents. These pleased him so much and 



* Even if a copy with a " privilege " were produced, it would not afford 

 a very satisfactory decision. Decker and Henrion may very well divide the 

 honour. 



t Nothing shows better the fear with which arithmetical calculations 

 were regarded than the eagerness with which the Rabdologia was welcomed. 

 I have seen an Itahan translation by Locatello, Verona, 162.3, and an edi- 

 tion by Ursmus, 1623 (not 1723 as given by Rogg), as well as references 

 to two or three others (in booksellers' lists), besides subsequent Englis^h 

 editions. 



