L'Economie sociale de la France sous Henri IV

SUBJECT AREA: Canals, Textiles

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Cosnier was probably an Angevin as he had property in Tours although he lived in Paris; his father was valet de chambre to King Henri IV. Although he qualified as an engineer, he was primarily a man of ideas. On 23 December 1603 he obtained a grant to establish silkworm breeding, or sericulture, in Poitou by introducing 100,000 mulberry plants, together with 200 oz (5.7 kg) of mulberry seed. He had 2,000 instruction leaflets on silkworm breeding printed, but his project collapsed when the Poitevins refused to co-operate. Cosnier then distributed the plants and seeds to other parts of France. The same year he approached Henri IV with the proposal to build a canal from the Loire to the Seine, partly via the Loing, from Briare to Montargis. On the king's acceptance of his proposal, Cosnier on 11 March 1604 undertook to complete the canal, which necessitated crossing the ridge between the two rivers, over a three-year period for 505,000 livres. The Canal de Briare, as it became known, with thirty-six locks including the flight of seven at Rogny, was almost complete in 1610; however, the death of Henri IV led to its abandonment. Cosnier offered to complete it at his own expense, but his offer was refused. Instead, his accounts were examined and it was found that he had already exceeded his authorized credits by 35,000 livres. In settlement, after some quibbling, he was awarded the two seigneuries of Trousse near Briare. Cosnier then suggested encircling the Paris suburbs with a canal which would not only be navigable but would also provide a water supply for fountains and drains. His proposal was accepted in 1618, but the works were never started. In the 1620s the marquis d'Effiet proposed the completion of the Canal de Briare and Cosnier was invited to resume work. Before anything more could be done Cosnier died, some time between July 1629 and March 1630, and the work was again abandoned. The canal was ultimately completed by Boutheroue in 1642, but the seven locks at Rogny remain a dramatic monument to Cosnier's ability.

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