==Encyclopædia Edinensis== 
 Perhaps you can help. It was published in six volumes all right, but that was a dozen years after it was announced in 1815. It is obvious that there was a part-published version first. I haven't been able to turn up a clear reference to when that started, though. 

 Of the contributors, not so many seem obviously notable. I have a draft for William Galbraith (mathematician), which doesn't need much work now. Apart from that I don't hold out much hope. But you might have something more.