Openings of the windmill towers 

All windmill towers have openings to allow access to the working floor and allow materials to go into and out of the windmill structure. Openings have specific functions within the windmill. Each windmill has at least three openings and a variety of configurations exist. You can learn more about what this post does not include about windows and hearths in windmill towers.

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What are the openings in a windmill and how did this work in practice? 

The openings found in the masonry tower of the windmill served a variety of purposes. In the windmills of St. Croix, all had a main entrance, invariably facing west, and all had a tall, slender opening for changing the main shaft, here called the machine slot. Also, there was always an opening to accommodate a juice trough. Other openings found in various windmills included those for discarding the crushed cane or “bagasse,” as well as windows facing both east and west, and a hearth.

The rotational direction of the sails impacted the configuration of the rollers since the fresh cane was inserted between the king and the sugar roller and removed from the bagasse roller. This was reflected by the configuration of the openings of the windmill, as there was a specific opening for the juice trough as well as one to discard the bagasse. In some mills, the rotational direction of the sails was most
likely changed, causing the machinery to be adjusted; this is evidenced by a newer opening in the masonry tower, bordered by a different material from the other openings, for discarding the bagasse.

How are the windmill openings positioned? 

Windmill tower openings have consistent appearance and orientation. Each mill has a main entrance, machine slot, and bagasse opening. Most towers also have a juice trough opening. While many towers also have windows, hearths, and basements, those will be covered in other blog posts.

The main entrance invariably faced west, with practical in the lee of the wind enabling cane deliveries without worry of interference from rotating sails. Set perpendicular in the tower, the tall, slender machine slot would oppose the juice trough opening. The orientation of these openings would never vary from due north-south by more than 30 degrees. On either side of the main entrance, and sometimes both, the opening for discarding bagasse was located. Each opening had a distinct purpose during cane crushing and to facilitate maintenance.

Main entrances and their access ramps

St. Croix windmills consistently place the main entrance facing west, allowing unimpeded access to the mill while the sails are in motion, even if the prevailing winds came from the northeast or southeast. This orientation also allowed the sails to be turned out of the wind and secured from moving while still allowing access to the main entrance.

The approach to the main entrance varies between windmills. Often, access was flush with the ground on the lee side. Windmills built on the windward, eastern sides of hills or ridges, facilitated this style of access.

Some towers required an earthen or masonry ramp, especially where the mill needed a higher foundation (on flatter ground, such as on the south shore). Wooden ramps have disappeared over time, often leaving behind masonry supports. Masonry ramp supports can be seen at Carlton (WE), Diamond (PQ), Anguilla (KQ), and Annas Hope (CQ).

Masonry ramps became more sophisticated in later mills, sometimes incorporating storage space. Mills with simple, straight ramps include Campo Rico (WE), Orange Grove (WE), and Negro Bay (PQ) More sophisticated examples include Wills Bay (NA), Little La Grange (WE), and Hermitage (KQ), which included storage areas underneath the ramps.

Another approach to the entrance was a ramp, which went over a tunnel through which carts carrying bagasse traveled. Examples include Rose Hill (NA), Barren Spot (QQ), Castle Coakley (QQ), and Work and Rest (QQ). In some mills, a ramp into the mill has a perpendicular section with 2 access points paired with a full basement under the mill. This ramp and basement provided extensive storage space underneath as well as creating a distinctive appearance to the windmill. Viewed from above, the windmill was connected to ramp work which looked like a “T.” The top bar of the “T” was a pair of ramps going from the ground and rising to nearly the floor level of the mill. The vertical bar of the “T” went straight into the working floor of the mill and was above an opening which went into the basement of the mill. Examples include Hope and Carlton Land (WE), Two Brothers (WE) and The Sight (EA). Most sophisticated for this design was the ramp work and windmill at Diamond-Keturah (CQ).

Two Brothers windmill basement interior facing east featuring the center pillar supporting the mill above.
Two Brothers windmill basement interior facing east featuring the center pillar supporting the mill above.

Size differences between juice trough openings

The juice trough opening provided an outlet for the cane juice from the windmill. This juice would flow by gravity through a trough down to the factory. In general, it was built on either the north or south side of the windmill. This opening was built in a wide variety of dimensions in St. Croix windmills. Evidence of the receiver, a 400-to-500-gallon vessel that initially collected the juice, can be seen by a large rectangular depression around the juice trough opening.

The standard juice trough opening is the round arch, such as is found at Coakley Bay (EB). However, this shape was not entirely consistent, as illustrated by “bell shaped” openings. This bell shape was created with the provision for floor beams to extend all the way through the opening. These beams were instrumental in keeping in place the bridge that held the crushing rollers. Along the floor and in the wall opposite the bell shape, it is often possible to find the remnants of the other anchors for the beams. Examples of the bell-shaped opening are at Prospect Hill (NA), Bonne Esperance (QQ), Castle Coakley (QQ), and Golden Rock (CQ).

Windmill tower silhouetted against blue sky. Stone finish is dark grey with mortar being light cream color. Arched opening in the center of the image.
Golden Rock windmill exterior from the north featuring the juice trough opening. The machine slot can be seen through the far side of the mill wall. The partial collapse of the upper reaches of the mill are evident with the sloping top of the wall.

The height of the juice trough opening is not consistent among the windmills of St. Croix. Because primarily the juice trough passed through this opening, some of the large openings may be considered excessive. In some of the mills, only a juice trough passed through the opening and, therefore, it is very short. Examples of shorter height juice trough openings can be found at Barren Spot (KQ), Sion Hill (QQ), and Golden Rock (CQ). The size of the juice trough opening was also mediated by the location of the “receiver” inside many windmills, which exaggerate the height of tall juice trough openings. Reflections of this can be seen clearly at Ham’s Bay (NA), Becks Grove (PQ), Southgate (EA), and Cotton Valley (EB) as a substantial section of the floor is recessed several feet adjacent to the sluice opening to accommodate the 400–500-gallon receiver.

As an extreme comparison, some of the windmills on the island of St. Kitts presented an entirely different approach to the juice trough opening. A one-foot square opening allowed only enough space for a trough to exit.

Alternative configurations were created at several windmills. The juice trough opening in the windmill at Hard Labor (PQ) was placed in the east side. The juice trough passed through a brick-lined tunnel which was embedded in the ground to pass below the rotating sails. The factory was apparently in the valley below. Similarly, the mill at Cane Bay (NB) had an opening below the window in the east face of the mill. This opening appears to have accommodated the juice trough as the floor suggests a receiver was present at this opening.

Cane Bay windmill interior facing east featuring the juice trough opening.
Cane Bay windmill interior facing east featuring the hearth, window, and below is a juice trough opening.

At Coakley Bay (EB), two matching slots were built into the exterior of the mill in the juice trough opening. This appears to have supported some sort of beam. Given its height, close to the top of the arch of the opening, this cross beam was not likely used for supporting the juice trough and may have been used to close up the mill when it was not being used to crush cane. In the case of Coakley Bay, this may have protected machinery, given the proximity to the sea and the destructive force of the salt spray on metal.

The Machine Slot

The machine slot in most mills is directly opposite the juice trough opening on a north-south axis. This tall, slender opening was designed for access when replacing the long central drive shaft. Given the need for periodic maintenance, the machine slot is found in all windmills. This opening was built to varying heights in different windmills and was generally about three feet wide. This opening appears to have been very useful in certain windmills, as other modifications, which will be discussed in another blog post, suggest wholesale changes of machinery during the operational life of the mill.

Little La Grange windmill exterior from the southeast featuring the machine slot.
Little La Grange windmill exterior from the southeast featuring the machine slot. Much of the brick lining the opening was removed, leaving the fieldstone. The hole to the bottom right of the machine slot is a timber slot that would have anchored a timber to tie off ropes used to move the top cap and secure the sails when the mill did not operate.

To protect both the masonry and the machinery as materials passed through, evidence exists that wooden stairs and wooden beams at the top of the opening’s arch were often employed. Sometimes, the masonry base of machine slot stairs are still in excellent condition, although where no wooden stairs are left, only holes in the walls where the wood was secured remain. Wood treatment can still be found at several mills, including Prospect Hill (NA), Salt River (NB), Clifton Hill (KQ), Concordia (QQ), Montpellier (QQ), Sion Hill (QQ), Bellevue (CQ), Orange Grove (CQ), and Mount Roepstorff and Southgate Farm (EA).

The Green Kay windmill highlight of the machine slot stairs.
Green Kay windmill highlight of the machine slot stairs. The missing stones on the walls of the machine slot indicate where wooden beams would have added a layer on the stairs.

The windmill at Diamond-Keturah (CQ), as well as Marienhoj (EA), are two of the best examples of staircases, with 10 distinct risers in each case. Some windmills such as the one at Hard Labor (PQ) have no evidence of stairs being incorporated into the windmill, as the mill floor is flush with the outside ground. In one case where stairs are not found, Ham’s Bay (NA) combines the function of the machine slot and the juice trough opening; the receiver was evidently intended to reside inside the windmill as a large rectangular recess takes the place of stairs.

The Bagasse Openings

The products of crushing cane were the juice which left through the juice trough opening and the fibrous remains of the crushed cane, or bagasse. Crushing cane created a lot of bagasse, and it needed to be removed from the mill. Most mills had an opening to facilitate the removal of the bagasse from the mill. The use of bagasse as fuel for the sugar factory was adopted in Barbados, Nevis, and St. Kitts during the 1680s and 1690s, becoming widespread in the Lesser Antilles by the 1720s due to a relative shortage of firewood (Watts, pp. 398-399). Most likely, the use of bagasse as a fuel started from the outset of the sugar industry on St. Croix.

The bagasse openings can be found on either side of the main entrance and sometimes on both sides. The reason for a second bagasse openings is not always completely clear. In general, one bagasse opening would have an outwardly sloping floor to facilitate the expulsion of the crushed cane material, or bagasse. A cart would be used to move this material to the bagasse shed for drying and storage. Therefore, the exterior approach to the windmill needed to accommodate these carts.

Arched opening from the interior with an outwardly sloping floor going through a masonry chute that is about 2 feet square. Other masonry walls and vegetation visible in the distance.
Castle Coakley north windmill interior facing southwest with a close up of the bagasse opening. The sloping chute allowed the crushed cane to be dropped into carts in the pit below and southwest of the tower. The masonry walls right outside the window delineated the pit and provided a safety factor.

The earlier windmills of St. Croix generally had only one bagasse opening. However, later modifications often created a second opening. Adding a second bagasse opening would indicate a change in the rotational direction of the sails, perhaps suggesting that a more efficient means of catching the prevailing breezes was observed and implemented. The later opening at Wills Bay (NA) can be distinguished by virtue of having a different material lining the arch, typically yellow bricks, than the other openings of the windmill, which were often lined with cut sandstone blocks.

Arched opening centered in the image through which the arched juice trough opening visible on the far side. The tall, narrow machine slot partially visible on the right and main entrance on the left. Weedy vegetation in foreground.
Cane Garden windmill exterior from the southwest featuring the bagasse opening. The floor slopes outward to facilitate the removal of the crushed cane from the windmill. The recess to the lower right would have held a timber used to tie off the sails when the windmill was not in operation.

In some cases, two bagasse openings appear to have been built into the mill, one with a sloped floor and one with a flat floor. It is difficult to be certain in many cases if one of these floors originally had a sloped floor, which was blocked up later. If these were never functional bagasse openings, they may have been included for several reasons: access for parts and tools, facilitating movement into and out of the mill while it was operating, or architectural symmetry.

In some later mills, dual bagasse openings were apparently incorporated into the initial design of the mill. All openings in these mills have the same trim and uniform dimensions at Becks Grove (PQ) and Coakley Bay (EB). This might indicate a realization that conditions may change, with the result that the rotational direction of the sails should also change. It would therefore be easier to incorporate flexibility into the initial design by including dual bagasse openings rather than to create a new opening after the masonry tower was completed.

Second bagasse openings could also provide for movement into and out of the mill while it was in operation. The mill would get crowded with people and material while in operation, with uncrushed as well as crushed cane as well as the equipment. There were at least three people working in the windmill: one to feed the raw canes into the front of the rollers, one to feed the canes back through the other side of the rollers, and one to remove the bagasse from the mill (Haagensen, p. 28). It may have been useful to have an additional opening for people to move into and out of the mill. In mills at Negro Bay (PQ) and the south mill at Castle Coakley (QQ), the second bagasse opening was flush with the outside ground level.

Beneath the bagasse opening outside the mill, some mills had a bagasse pit. These fairly round, 15 to 20 feet in diameter structures were characterized by masonry walls several feet high. There was often a passage heading west from the bagasse pit, generally beneath an archway which supported a ramp heading into the windmill. Carts would use this passage to access the bagasse pit. While in the bagasse pit, the carts would be filled with bagasse for removal from the mill area. Prime examples of bagasse pits survive at Rose Hill (NA), Salt River (NB), Barren Spot (QQ), both mills at Castle Coakley (QQ), Concordia (QQ), and Work and Rest (QQ).

Top half of a windmill tower beyond a 15-20 foot high retaining wall. The wall has an arched opening creating a tunnel about 50 feet long.
Castle Coakley south windmill exterior from the west featuring the bagasse pit approach. Carts would have gone through this tunnel to the pit beyond to collect the bagasse.

The bagasse pits at Castle Coakley merit mention, as a massive amount of masonry was incorporated in them. The twin mills there both have sizable bagasse pits, with the shorter mill to the north having an enormous one nearly 25 feet deep. If the 1833 Frederik Von Scholten watercolor of Castle Coakley accurately depicts plantation structures, the shorter northern mill was built at this time, while an animal mill was in operation at the site of the taller, southern mill. As well, this watercolor does not give any indication of the elaborate bagasse pits. This would suggest that the second mill was built after 1833, a late time for windmill construction. Only one windmill is depicted on the Oxholm map, indicating that one of the mills was built after 1794. The massive masonry work to create the bagasse pits was likely done during or after the construction of the second mill. This massive investment in terms of labor may have indicated that this was an early move to centralized cane processing.

1833 von Scholten watercolor of estate Castle Coakley showing a windmill and an animal mill

We love feedback about the site and hearing from those who are inspired in a variety of ways by information provided here. You can reach us via email at info@stcroixwindmills.org