Canadian Historic Sites: Occasional Papers in Archaeology and History No. 12

Lime Preparation at 18th-Century Louisbourg

by Charles S. Lindsay

Slaking at Louisbourg

There is virtually no documentary evidence concerned with slaking at Louisbourg; however, an early report to France on work to be done at Port Dauphin, where lime was quarried for Louisbourg construction projects, mentions the erection of kilns for burning the lime there and the digging of slaking pits. The report states that the lime would be slaked in small pits to turn it to a milky texture which would then be poured into storage pits 18 pieds square and 4 pieds deep.¹

Some plans depict slaking pits at Louisbourg, though it is not always possible to determine the type.

1) A plan drawn in 1720 shows a lime-kiln astride the King's-Dauphin curtain line with a storage pit and a slaking pit (Fig. 25, a). The larger pit, approximately 28.0 ft. by 24.0 ft., is joined to the smaller pit at its southern end. This arrangement is precisely that described by Blondel, the smaller pit being the place where the slaking was carried out and the larger one being a reservoir. Water for slaking could be obtained from the nearby pond. A later plan, drawn in 1731, shows two large pits and no small slaking pit (Fig. 25. b).

25 Historical drawings of slaking pits at Louisbourg. a, shows a slaking and a storage pit for the kilns astride the King's-Dauphin curtain. Taken from a plan entitled "Plan de Louisbourg Avec Ses Augmentations faites pendant l'année 1720" (Archives du Génie); b, pits for the same kilns 11 years later. Taken from a plan entitled "Plan Pour Servir au Project Representé en Jaune du Revetment du Quay du Port de la Ville de Louisbourg à l'isle Royalle, 1731" (Archives du Génie); c, shows two slaking pits and three storage pits at the Royal Battery. A stream (C) has been canalised to run water to a small pond near the slaking pits from which the water was hoisted by bucket into a chute which directed it into the slaking pit. Taken from a plan entitled "Plan de la Batterie Royale Avec Ses Environs Pour Servir au Projet de 1726" (Archives Nationales); d, shows two pits for the Rochefort Point kilns. Taken from a plan entitled "Louisbourg 1752: Plan de la Pointe à Rochefort (Archives Nationales); e, shows two pits described as "Old Tann spits" near the pond outside the Dauphin demi-bastion. They were probably lime-slaking pits, since there was no tannery at Louisbourg. Taken from a plan entitled "A Plan of Louisbourg Survey'd and Drawn for His Excellency the Honble. Major General Thos. Gage Commander in Chief of His Majesty's Forces in America," 1767. (Public Archives of Canada).

2) A plan drawn in 1725 of the lime-kiln and slaking pits at the Royal Battery again shows small pits for slaking connected to larger storage pits (Fig. 25, c). In this case there are two large (30 ft. by 20 ft.) conjoined rectangular storage pits to the west of the two small slaking pits, and one irregular storage pit to the east. There does not appear to be any connecting channel between the two rectangular pits, though this may have been below the surface. Leading in from the east was a canal dug to bring water down to a small pond next to the slaking pits. Here a frame was erected with a pivoting arm, on one end of which was a rope attached to a bucket. The bucket was dipped into the pond, then raised and the water tipped into a trough standing on trestles which conveyed the water into the slaking pit.

3) A third plan drawn in 1752 (Fig. 25, d) shows two pits approximately 150 ft. from the two kilns near Roche fort Point. The pits are both the same size, beside each other, and without slaking pits attached. This simplicity is probably to be attributed to the schematic nature of the plan.

4) There are no indications either in the documents or on the plans of slaking pits for the kilns in Block 1 and in the faubourg. In the faubourg two rectangular depressions approximately 250 ft. southwest of the kiln may have been storage pits, though they do not appear on any plans until 1767, when they are described as "Old Tann Pits" (Fig. 25, e), a mistaken identification probably derived from the use of lime in the tanning process. There was no tannery at Louisbourg at this time.