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

Lime Preparation at 18th-Century Louisbourg

by Charles S. Lindsay

Other Lime-kilns at Louisbourg

At least six lime-kilns besides the one in the faubourg are known to have existed at Louisbourg during the French occupation (Fig. 22). In probable chronological order they are:

1) Two lime-kilns (Fig. 23, a) built astride the line of the King's-Dauphin curtain. These were built for the construction work on the King's Bastion and Barracks, and had been demolished by the time the curtain wall was begun in 1735. Nothing is known about the kilns beyond the plan drawings and the accompanying view (Fig. 23, b). Except that they were square based, not circular, they appear to be standard types as shown in Figure 1, 3, 4, good examples of kilns erected near the site of the construction work.

2) The Royal Battery lime-kiln depicted in a detailed view of the construction work there in 1725 (Fig. 23. c). The view shows the top of the kiln projecting approximately 6 ft. above the surface, and also shows the slaking pits. The date of destruction of this kiln is not known, but it probably was abandoned when construction of the battery was finished.

22 Distribution map of lime-kilns and slaking pits at Louisbourg. 1, Rochefort Point kilns and slaking pits; 2, kiln near Block 46; 3, King's-Dauphin Curtain kilns and slaking pits; 4, possible slaking pits for Faubourg kiln; 5, Faubourg kiln; 6, Royal Battery kiln. (click on image for a PDF version)

3) A lime-kiln built about 1737 just behind the King's-Dauphin curtain west of Block 1 inside the town (Fig. 23, d). This kiln seems to have been built to replace those that had been astride the King's-Dauphin curtain. The owner of a nearby house, Joseph Lartique, complained that the fumes from the kiln were ruining his health; however, since this was the only lime-kiln in operation at Louisbourg at the time, he had to put up with the inconvenience.1 The lime-kiln was excavated in 1967 by William A. Westbury, and was found to be a simple circular structure (Fig. 24). All that remained was that part of the kiln that had been subterranean. The kiln was 23 ft. in over-all diameter, with a wall 3.5 ft. thick, creating a furnace 16 ft. in diameter. On the north side the wall thickened out at the drawhole, the sill of which was 3 ft. above the dirt floor of the kiln. Outside, the ground surface had been 5 ft. above the floor, so the stone-lined passageway to the drawhole was approximately 2 ft. below ground level.

23 Historical drawings of lime kilns at Louisbourg, a and b, show lime-kilns astride the King's-Dauphin curtain. Taken from a plan entitled "Plan Pour Servir as Projet Representé en Jaune du Revetment du Quay du Port de la Ville de Louisbourg en l'isle Royalle," 1731 (Archives du Génie); c, shows the Royal Battery lime-kiln. Taken from a plan entitled "Plan de la Batterie Royale Avec Ses Environs Pour Servir au Projet de 1726" (Archives Nationales); d, shows the kiln west of Block I. Taken from a plan entitled "Partie de la Ville de Louisbourg" (Archives Nationales); e, shows the lime-kilns at Rochefort Point. Taken from a plan entitled "Louisbourg 1752; Plan de la Pointe à Rochefort" (Archives Nationales); f, shows one of the Rochefort Point kilns. Taken from a plan entitled "Plan du Cap breton dit Louisbourg Avec ces environs Pries par Lamiralle Bockoune le 26 juillet 1758" (Library of Congress).

A U-shaped iron band with short horizontal terminals at either end lay on the floor of the kiln. The length from apex to terminal was 2 ft. This band would have adequately served as a support for the arch of the drawhole.

From the remains this kiln appears to have been very similar to the flare kilns from Provence (Fig. 3, a). The floor some distance below the sill level, the shallow sunken passageway, the cylindrical furnace and the free-standing walls all point to the Provence kilns as the prototype for this one.

4) Two kilns at Rochefort Point, outside the eastern defences of the town, have a rather vague history both in place and time. Various maps show the kilns at different places, but the most probable site is near the harbour side of the point on a low rise to the east of the pond in front of the Maurepas Bastion (Fig. 23, e). Although the erection of these kilns was proposed in 1738, they do not appear on any plans until 1745 but are described as "old lime-kilns" in 1746.2 They were still in existence in 1758, but it is not known whether they were still in operation at that time. An interesting, if somewhat impressionistic, view of the area in 1758 shows one of these lime-kilns (Fig. 23, f). In appearance it is almost exactly similar to that in Figure 1, 11, but seems to be free-standing rather than subterranean.

Little is known about the operation of lime-kilns at Louisbourg, though something can be inferred from incidental remarks by Franquet in letters to the Minister of Marine in France.

In a highly critical account of the cost of lime-burning, Franquet, in 1751, stated that the lime-kiln (at this date almost certainly one of those at Rochefort Point) was badly built, would hold only 2.25 cubic toisés of limestone, and was poorly serviced by the soldiers.3 This same account describes payments made to the soldiers for operating the kiln. They were paid for, among other things, constructing an arch in the kiln 5 pieds high and capable of taking the weight of the limestone. This indicates that the kiln was being fired as a flare kiln. In a later passage he notes that if the kiln were well-built, it would not need such an arch, suggesting that he thought that a "well-built" kiln should be fired as a running kiln. The soldiers were also paid for breaking the stone, loading the kiln, watching and feeding the fire day and night and removing and slaking the lime. Three men were occupied at this task for 11 days and the 4 nights when the fire was alight and had to be constantly tended.

Franquet's major complaint about the lime-burning was centred around the incompetence of the men operating the kiln. He noted that as much as one-fifth of each load was unburned because the stone was not properly broken and loaded, so the heat could not penetrate completely. Also the arch, being badly built, often collapsed during the firing, ruining the load of limestone.

Documentary and archaeological evidence show that both wood and coal were used as fuels at Louisbourg. In 1718 it was noted that mortar used in waterlogged areas was mixed with the ashes from the coal with which the lime was burnt.4 In 1752, Franquet suggested as an economy measure that coal be used for burning the lime instead of wood and fascines as had been used at the Royal Battery kiln.5 The surface of the passageway to the entrance of the first kiln in the faubourg was covered with crushed charcoal fragments. The ground surface outside the passageway, on top of the continuation of the raised floor level to the second kiln, contained, among some boulders of partly burnt limestone, some fragments of coal and charcoal. Since secondary sources suggest that coal is used only in running kilns, the appearance of coal fragments associated with the second kiln reinforces the argument for interpreting this as a running kiln.

Since the cost of lime had risen from 4 livres per barrel in 1725 to over 8 livres per barrel in 1751, Franquet wanted to initiate savings which he suggested could be made by the use of coal instead of wood, burning the lime at the limestone quarries, and slaking it before transport to the construction site. Since the limestone quarries were at Spanish Bay (Sydney), 26 miles away. and Main-à-Dieu, 12 miles away, the transport of liquid lime would have been a major problem. Nonetheless, Franquet insisted that it could be done after the lime had been allowed to settle a little. We do not know whether Franquet succeeded in convincing the minister of the feasibility of his scheme.

24 Remains of the excavated lime-kiln west of Block I.

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