This is the more to be wondered at as he was not a professed engineer.

After him followed Spekel, a native of Strasburg, who died in 1589.

His writings are valuable as showing the state of the art at that time, and the changes which he himself introduced.

He was an engineer of much practical knowledge and experience, having assisted at the sieges of Malta, Golletta, Vienna, Jula, Nicosia, Famagusta, &c.
The first French engineer who wrote on fortification was Errard de Bar-le-Duc, who published near the close of the sixteenth century.

As an engineer, he was rivalled by Chatillon, a man of distinguished merit.
Errard fortified Amiens, built a part of the castle of Sedan, and a portion of the defences of Calais.