Your friend might enjoy it in vintage English: ... another edition of the *Methodus differentialis* [was published] in London in 1764; and a translation of the latter into English by Halliday in London in 1749. It's irritating that Stirling didn't "translate" it himself. But even without the risk of a second-rate translation, the pioneers in a field are hard to learn from. Their words don't quite mean the same as ours, and their understanding was sometimes less complete than we have come to possess. In any event, http://en.wikipedia.org/wiki/James_Stirling_%28mathematician%29 is fascinating. --rwg