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New Method of Division for Mathematical and Astronomical Instruments
M. le Duc De Chaulnes, 1768

The Duc de Chaulnes’ innovations and achievements in the development of the circular and linear dividing engine have always been overshadowed by those of Jesse Ramsden.   This was the result of his success based on two main factors — Ramsden’s superior mechanical skills and his understanding of mechanical processes which led to his receiving an award from the Board of Longitude in Britain.  However, the Duc de Chaulnes’ technique and approach was superior to Ramsden’s and was later adopted by Edward Troughton for his 1806 circular dividing engine and by Henry Kater in the technique he proposed in 1814.  

In 1768 Chaulnes published  Nouvelle Methode pour Diviser les Instruments de Mathmatique et d'Astronomie, which minutely illustrated every component of the circular and linear engines in 15 plates. A very important new element which Chaulnes incorporated was a mechanical means of scribing the lines. A similar mechanism was used on his 1765 machine but was not described.  The new mechanism was complex and one wonders whether this was more of a limiting factor in the engines' use than the method of moving the piece to be divided.  The scribing tool could be balanced by a small reservoir and was activated by a handle and pulley system.  There were screws for the adjustment of the radial position and stroke length of the scriber, and the whole apparatus was mounted on a base in such a way that it could be swung through an angle of 45° from the centre position with the centre of rotation corresponding with the axis of the wheel.

Printed in large format with attention to detail, such as margins, leading, and type choices including font italics as close as possible to be sympathetic to the original layout and delicacy, which was the norm in the mid-18th century. The final size of the book is 11" x 17" (28cm x 43cm).

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