This takes him twenty-six years back.

It was at that time that, being in Holland, which is his native country, and having till then not been in trade at all, he received from England a copy of the _Arithmetica Logarithmica_ of the famous mathematician Henry Briggs [published 1624].

Greatly enamoured with this work and with the whole new science of Logarithms, and observing that Briggs had given the Logarithms for numbers only from 1 to 20,000, and then from 90,000 to 100,000, he had set himself to fill up the gap by finding the Logarithms for numbers from 20,000 to 90,000, and had had the satisfaction, in an incredibly short space of time, of bringing out the result [in an extended edition of Briggs's book published at Gouda, 1628].

Briggs and the English mathematicians were highly gratified, and Ulac was asked to publish also Briggs's _Trigonometria Britannica_.

This also he had done [at Gouda in 1633, Briggs having died in 1630, and left the work in charge of his friend Henry Gellibrand]; after which he had engaged in the heavy labour of converting into Logarithms the Sines and Tangents to a Radius of 10,000,000,000 given in the _Opus Palatinum_, and had issued the same under the title _Trigonometria Artificialis_.