The gas chamber in Crematorium II in Birkenau was built following conventional construction methods of the time. Several unusual features, however, were encountered during our research visits. Those not explained previously will be discussed now. We do not touch upon the crematorium proper or on the undressing chamber in this study.
The gas chamber was a fairly simple structure. The floor was cast reinforced concrete with appropriate drainage outlets. The seven support columns are also of reinforced concrete mounted on column footings under the floor slab. The walls are hard-fired conventional brick held together with mortar. The columns are attached to a reinforced concrete beam that spans the entire length of the gas chamber. The roof is cast reinforced concrete with a single layer of damp-proofing and a 2-cm. fine sand-concrete topping. Total thickness of the slab is 20 cm. The design is not remarkable except that the surface of the floor is approximately 1.6 m underground, the top of the roof 0.8 m aboveground (due to the uneven placement of the fill dirt, the exact height of "ground level" is difficult to specify).
The drawings and the remains of the gas chamber in Crematorium II reveals several other unusual features (some never before discussed):
a) There are neither windows nor any form of natural illumination or ventilation in the chamber.
b) There are no stairs or ramps leading down into the chamber.
c) Access to the chamber was possible only through a door on the eastern portion of the north wall that connected to the actual crematorium. (Points a, b, and c have been amply discussed elsewhere.)
d) The brick walls on the east and west sides have a large, hollow channel that runs for their entire length (see Figure 2a).
e) A number of small wire loops 60 cm apart are attached to the ceiling along the full length of the chamber, on both sides of the support beam, and 100 cm from the brick walls.
Points d) and e) have also been described elsewhere. According to Pressac's analysis of the original construction drawings, the ventilation ducts inside the brick wall were employed to replace the air in the gas chamber, whereas triangular ducts formed of plywood fixed to the ceiling and both the north and south walls were designed to introduce air into the chamber. The chamber's ventilation system has been extensively discussed.16
f) The remnants of three large, square holes (1, 2, and 4) can be seen on the surface of the roof. The approximate location of Hole 3 has been described in Part I of this study.
g) Steel reinforcing bars (rebar) on the roof were cut during the construction phase (some are also cut and bent in an L-shape) at the points where they intersect the introduction holes. Rebar of 12-15 mm diameter was laid on the roof in rows approximately 15 cm apart in both south-north and east-west directions, forming a nearly square grid on to which concrete was poured. The grid was anchored to the central beam and to a peripheral rebar structure with traditional U-bends. Explosive forces caused breaks in the grid when SS sappers demolished the chamber. Many of the broken bars were drawn and stretched out to a sharp point by the explosive forces, whereas other bars appear purposely cut to form a square pattern precisely 50x50 cm where the Zyklon B introduction holes are still found.
h) A small rectangular 4 x 10 cm aperture was cast at the same time, penetrating the roof into the chamber below (Figure 19). The aperture is 3 m north of column 5, and 2.65 m from the eastern edge of the roof slab. The function of this hole remains unknown. It was possibly fitted with a removable gasket that allowed the insertion of a detector to test the concentration of gas: it is known that the crematoriums were equipped for this purpose.17
i) A number of small (approx 10 x 15 x 4 cm), rectangular cast indentations can be seen in the ceiling of the gas chamber. At least six of these are visible in those portions of the ceiling presently accessible from below. Some of the indentations have wooden blocks with visible rusted nails or screws. The indentations are uniformly placed and lined up on both sides of the support columns, 2 m from the edge of the support beam and approximately 3 m north of the southern wall as far to the north as can be seen in the ruins. It is to the wooden blocks that fake showerheads reportedly were affixed (Figures 20).
One important detail must be emphasized: the indentations containing the wooden blocks were purposely built into the ceiling of the gas chamber from the very moment that the roof was built. It might be argued that these blocks were used to support the reinforcing bar (slab bolster) before concrete was poured onto the roof. Various arguments dispel this notion:
- Supports for reinforcing bars are typically small pieces of broken concrete or stone that would be incorporated into the concrete mixture and be invisible from below
- Concrete is a porous material with a highly alkaline solution in the pores; this solution keeps the rebar from rusting and weakening the structure: no engineer would deliberately use wood slab bolsters because that would allow water to reach the rebar
- Except for one upper corner in one of the indentations there is no rebar in the hollows formed by the wooden blocks.
- The wooden blocks were carefully lined up in the same orientation and at exactly the same distance from each other and from the central beam.
- The surviving wooden blocks all show signs of a screw or similar object inserted in their center as if to support something within the gas chamber.
j) A large number of small wooden support blocks are attached to both sides of the central reinforced concrete beam. Several of these blocks still have attached to them small Bakelite plastic supports of the sort used to conduct electric cable. The support blocks are visible all the way to the southern end of the support beam, some 2-3 m beyond the first showerhead block. Electric wires were most probably carried on these supports to provide current for illumination. Analogous supports in other parts of the concentration camp (e.g., Crematorium I) bear electrical cables (Figure 21).
k) We found a small disk 8 cm in diameter imbedded in the path less than one meter to the east of the gas chamber. The disk shows many small perforations (more readily seen on the reverse side) in a manner consistent with the front plate of a showerhead. The holes are of such a minuscule size-many do not seem to perforate the plate at all-that it is unlikely that much, if any, water could have flowed through them (Figures 22 and 23). The sheet metal shows signs of having been galvanized, which would have inhibited rusting and made a "showerhead" more convincing. There is no evidence of any plumbing facilities in the gas chamber of Crematorium II. Given the convergence of evidence from eyewitnesses and records held in the archives of the Auschwitz Birkenau State Museum,18 this fixture undoubtedly formed part of the elaborate plan to keep the victims ignorant of their fate as long as possible.
We now turn to some of the photographs taken from Allied and German airplanes, showing their relation to the physical layout of the crematorium, and especially to the Zyklon introduction holes.
It is impossible to observe the Zyklon holes themselves in any of the aerial photographs. To realize why, observe the gas chamber roof in Figure 24, which is the best suitable aerial photograph of Birkenau available. The gas chamber length is 30 m, while the holes' covers are about 60 x 60 cm. The low resolution and very strong granularity of the photograph don't allow direct observation of objects this size. However, certain phenomena associated with the holes can be identified. Also, given two overlapping photographs, both including the roof, the principle of stereo imaging (Faugeras imaging) may allow one to see more than is visible in a single image. We shall elaborate on this later. The best quality photo and the one that has attracted most attention was taken by an American plane on August 25, 1944; part of the photo is presented in Figures 7 and 24.19 A photograph of lesser quality, but still of interest, was taken from a German airplane on July 8, 1944 (Figure 25). The four dark, irregular smudges on the roof of the gas chamber in Figure 24 correspond to the location of the holes both in the Train Photograph (Figure 3) and to the physical findings (see the main part of this paper). However, it is clear that they are too large, and not in the correct shape, to represent the actual holes. In order to interpret the photo, we obtained the advice of Mr. Carroll Lucas, a leading expert with more than fifty years in aerial and satellite photo analysis.20
Mr. Lucas analyzed the two August 25 photos showing the roof of Crematorium II. The appearance of an object in two overlapping photographs allows reconstruction of its three-dimensional image by stereo imaging.21 Mr. Lucas employed magnifiers, a Richards light table with an attached Bausch & Lomb Zoom 70 microscope with a stereo attachment, a Carl Zeiss N-2 mirror stereoscope, and an Abrams 2-4 stereoscope Model CB-1, to analyze the photo appearing in Figure 24 and the successive previous frame taken during the same flight. After careful study Mr. Lucas identified four small objects within the smudges, all slightly elevated above the level of the roof. Stereo imaging allows observation of even small objects in grainy images, very difficult or impossible to detect in separate images, as is well-demonstrated by "random dot stereograms."22 In all probability, these correspond to the four "chimneys" above the holes in the roof, as clearly visible in the Train Photograph (Figure 4). Thus, the aerial photographs add further support to the witness testimonies and to the Train Photograph. With regard to the dark smudges and related findings Mr. Lucas summarized his conclusions as follows:
a) "The roof of the partially underground wing of the Crematorium contains four raised vents, possibly with covers larger than their exits."
b) "The four dark areas observed on the Crematorium II roof (on positive prints) are compacted soil, produced by the constant movement of personnel deployed on the roof, as they worked around the vents." This point will be discussed below.
c) "The thin dark lineation (on positive prints) interconnecting the dark areas is a path of compacted earth produced by personnel moving from vent to vent." (See Figure 24.)
d) "The dark area connecting this path to the edge of the roof from the vent nearest to the Crematorium roof is an extension of the path which shows where personnel gained access to the roof-possibly using a short ladder leaned against the roof." (See Figure 24.)
e) "The evidence provided by this analysis lends credence to the fact that the vents existed, and were used in a way consistent with statements from multiple witnesses."
In the 'Train Photograph' for example, one can clearly observe an as yet incomplete earth bank with a triangular cross-section located on the chamber's western edge, while there is no earth cover on the roof. Such an earth bank is visible in the May 31, 1944, photograph as well (Figure 26).
It is therefore reasonable to assume that between May 31 and July 8, the earth banks were flattened and the roof covered with earth. This newly placed earth was compacted by the SS-men climbing onto the roof and walking between the holes, thus resulting in the darkish path running through the chamber's center (item 3 in Lucas' analysis), and the short dark line extending west from the northernmost hole corresponds to the point at which the SS-men climbed on the roof (item 4 in Lucas' analysis). The path ends at the southernmost hole, indicating that the SS-men indeed climbed the roof at its northern end, and traversed it north-south-north. The SS-men spent more time moving in the vicinity of the holes, thus resulting in an area of compacted earth wider than the path that they treaded between the holes.
Further factors that may have contributed to the formation of the "smudges" in the photo:
a) Water may have been poured on the extracted Zyklon pellets in order to dissolve the Zyklon and reduce the danger of accidental inhalation. Hosing down the pellets would also cause the wet areas of the earth cover to appear darker, and could also have caused a different growth pattern of grass on the roof, resulting in a darker color; this is supported by the fact that areas with greenery appear darker in the photo (Figure 7).
b) It is possible that the inner cores of the wire mesh columns into which the Zyklon was inserted were not inside the chamber when the aerial photograph was taken, but were temporarily removed and propped against the small chimneys that housed the Zyklon insertion devices. One possible reason for removing the inner core is the following: since the gas chambers were hosed down after each gassing,23 it would have made sense to remove these inner cores while the hosing was taking place, in order to keep them dry. These inner cores, leaning on the small chimneys, could result in shadow patterns with an appearance such as that in the center of the smudges.
© Holocaust and Genocide Studies, Oxford University Press, Volume 18, Number 1, Spring 2004, pages 68-103. Used with permission.