Preface

The loss of his sight original: "Verlust seines Gesichtes"; referring to the author's total blindness awakened this thought within him, and driven by his ever-active mind, he did not delay in putting his resolution into practice. To this end, he chose for himself a young man whom he had brought with him from Berlin as an attendant. This young man could calculate quite proficiently, but otherwise did not have the slightest concept of mathematics: he was a tailor by trade The author emphasizes that even a layman could understand these complex principles if explained correctly and, regarding his natural ability, belonged among the mediocre minds. Notwithstanding this, he not only fully grasped everything that his great teacher dictated to him and ordered him to write, but through this process, he was enabled in a short time to