Ambiance of slowness. Brussels commercial gallery of the latter half of the 20 th century

. In this paper, I study the sensory-motor effects of Brussels commercial galleries’ ambiance in the latter half of the 20 th century. The analysis of two case studies (“Deux Portes” networked galleries and Agora Gallery) reveals the different logics of slow mobility acceleration and immobilisation at stake in the emerging modernist grammar of slow mobility. This grammar – in arrangement with the grammar of fast automobility – structures and stabilises the design of spaces for slowness next to the roadscape in spatial segregation of transport modes. There are accelerating and decelerating sensory dispositifs that define galleries both as punctual destination spaces that capture passers-by and as alternative paths for pedestrians: logics of multifunctionality, fast mobility accessibility and setting of an ambiance on the one hand, and logics of securement, spatial and qualitative continuities, on the other hand. Accelerating and decelerating dispositifs and logics facilitate movement to better keep the consumer captive. Then, I discuss the possible contribution of iconographic archives in research about past ambiances. They effectively acknowledge sensory-motor effects of ambiance but do not constitute an autonomous corpus to grasp sensitivity and reshape past ambiances. slow mobility and as a space of destination. The research gives that way a better understanding of the tension evolution, in mobility infrastructure development, between the fast and the slow mobility imaginary in Brussels.


How to grasp sensitivity?
Commercial galleries may be considered as sensitive environments. As every other space in which one moves, it gives rise - as "active potentiality" [1][2][3] - to perceptive orientations and specific motor behaviours: specific sensory-motor ways of being. In their work at CRESSON, Thibaud and Chelkoff analysed urban micro-morphologies that structure visual, luminous and sound experience and reveal dynamics and located relations between built forms and social uses. They have constituted knowledge about built forms from discursive perception records [1] and field studies of spatial behaviours in specific micro-morphologies [4].
The sensory-motor effects result from the expressive power of surfaces and the motor power of visual orientations. First, the sensitive environment is expressive, in the sense that it gives rise to action and makes itself available as occurrence, thanks to the surface quality: texture, luminosity, reflection, contrast… Second, the attentional gestures of observation, contemplation, examination that underlie the perceptive activity of the passer-by engage his full body, extending often what the sight outlines in movement [1]. Both steps and eye mobilities of the passer-by are considered in the concept of "mise en vue" (~exposure) that attempts to articulate spatial forms with social and perceptive forms [4]. It qualifies and characterises the different articulations of spatial behaviours and visual perceptions. Sensorymotor effects are described through the relation between the eye and the step, which dissociation is used as marker for urban environment quality [1]. Lower urban environment quality makes passers-by accelerate. In commercial galleries, "ambiance factors"interactions between built form and physical signals (luminous, sound…) - engage and disengage, that way, motor activity of passers-by.
In the latter half of the 20 th century, Brussels commercial galleries are defined both as alternative paths for pedestrians and as punctual destination spaces that capture the passerby. As in the Louvre Museum's underground [1], passers-by become subject in modernist commercial galleries to a paradoxical demand to circulate and to stay. This demand manifests through programmatic, regulatory and discursive dispositifs. This ambivalence appears in the materiality of galleries as well: in an articulation of sensitive acceleration and deceleration dispositifs that defines the "locomotor efficiency" of the commercial gallery as a "space of movement". It operates on ambiance.
When dealing with ambiances of the past, there is a methodological challenge. Most research on ambiance is based on discursive perception reports. Enunciation is perceived as a key element in the very perception of ambiance. To study ambiance of the past and to construct a "history of action in built forms", Ben Hadj Salem, for example, crossed spatial materiality and archives sources describing the social world and perceptions, on the one hand, with the somewhat impressionistic literature sources describing experiences, on the other hand [5]. His methodology relates that way to the history of environment. To grasp sensitivity is about forms of writing and restitution. There is a tension between the use of the first person, the phenomenological "I", and the use of the third, the scientific and hermeneutic "she", "he" or "they". With regards to the knowledge produced the last decades, is it possible to discuss "ambiance factors" of the past without falling back on this methodology (the phenomenological "I")? Is it conceivable to discuss past accelerating and decelerating ambiance considering iconographic archives, and to do so without lapsing into spatial overdeterminism? Iconographic archives effectively acknowledge sensory effects of light but they offer an overlooking point of view, less open to others' appreciation. It's somewhat already a hermeneutic restitution of the author's phenomenological perception.
The paper has multiple goals. First, I want to highlight the purpose of gaining insight in the meaning and the use of iconographic archives in research about accelerating and decelerating ambiances. Second, I aim for knowledge production about the "ambiance factors" that initiate or reduce motor activity in the Brussels commercial galleries of the latter half of the 20 th century, and how iconographic archives analysis makes those effects visible. I analyse the spatiality of the ambiance documented through original plans archives, architect's drawings and photos. I study the light and material effects that appear in the representations of (1) the networked commercial galleries of Louise and Toison d'Or avenues, and (2) the commercial Gallery Agora in the city centre.

Next to the roadscape. Spatial segregation of speed and slowness
Between 1950 and 1989, the built environment of Brussels underwent large transformations to adapt to the increasing automobility, and became part of a roadscape. This new park-like infrastructural urban landscape enforced by the state administration embodies a strong and prevailing fast mobility imaginary articulating functionality and aestheticism in the materiality of the city [6]. The urban renovation of Brussels at the agglomeration scale thus relied mainly on this imaginary [7] of fast mobility, documented through plans, models and technical discourses. The roadscape was based on logics that were iteratively emerging during a process of fast mobility imaginary stabilisation -"grammaticalisation". Those logics regulated the articulation between fast and slow mobilities through different regulatory and material dispositifs making an acceleration of automobility possible.
In this articulation, urban renovation also created spaces of slow mobility that embodied the emerging slow mobility imaginary. There are punctual spaces of destinations (pedestrian or restricted areas, parks, commercial galleries) where ends fast mobility infrastructure and that tends to "immobilise", to "capture" slow mobility paths. Those separate spaces were bordering fast mobility infrastructure in modal segregation system. In the 1950s, the model of the commercial gallery was indeed re-appropriated by the urban renovation stakeholders to modernise the city, rationalise the uses of spaces and operate a stronger spatial segregation between fast and slow mobility. The model of the commercial gallery matched the logic of "vertical zoning urbanism": internalisation in the built environment of the slow mobility paths and immobility spots, public transport stops and car parking lots, multiplication of ground level and available spaces for mobility flows (tunnels, bridges…). In that way, the design of commercial galleries implements dispositifs that tend to "immobilise", to "capture" slow mobility, increasing the destination dimension of the commercial gallery (improved car accessibility, multifunctional venue and services, comfort).
However, commercial galleries also form part of a passages tradition. Rainy city, Brussels was already marked by a construction tradition of covered commercial galleries since the 19 th century. It aimed at making the capital a "covered city" [8] emancipating pedestrians from the climate: Galerie du Commerce, Galerie de la Monnaie, Passage du Nord, Galerie du Parlement, Galeries Saint-Hubert… In that way, the design of galleries enforces dispositifs that, on the contrary, make slow mobility functional (spatial and qualitative continuity and securement of slow mobility paths).

A modern grammar of commercial slow mobility
The point here is to analyse the different logics of slow mobility acceleration and immobilisation at stake in the emerging modernist grammar of slow mobility. This grammar - in arrangement with the grammar of fast automobility - structures and stabilises the design of spaces for slowness next to the roadscape. It articulates accelerating and decelerating dispositifs and logics. I did so by analysing two case studies. The corpus is made of municipal archives (construction permit application and press reviews) † , and of project publication in specialised journals. Both case studies lie next to the roadscape. The first is located along a portion of the "highway croissant" formed by the Léopold II Boulevard, the † Archives de la Ville de Bruxelles  Petite Ceinture and the Louise Avenue. The "Deux Portes" neighbourhood is spread between two polarities from the upper city: the Porte de Namur and the Porte Louise. On one side, a night animated neighbourhood and, on the other side, a fancy commercial neighbourhood. The second case study is located at the heart of the Pentagon, next to the highway mini-ring around the Grand-Place designed in 1955 by Tekhné, along the boulevard of the railway Junction. It is bordering both the touristic and patrimonial neighbourhood of the Grand-Place and that of national institutions and mobility infrastructure (Mont des Arts, Royal Library, Central Station and Sabena terminus).  (Fig.1). The Agora Gallery (1963), the 19 th gallery located very close to the Grand-Place, is an interesting case study in terms of modernistic urbanism integration in the ancient urban fabric of the city centre.

Capture of slow mobility
Inside the spaces for slowness next to the roadscape, the modernist grammar of slow mobility sets up dispositifs that are part of the deceleration and immobilisation logics capturing slow mobility paths. Those logics make slow mobility infrastructure become meeting point where everything is about staying, as in American shopping malls. The logics involve multifunctionality, accessibility and ambiance setting. Galleries are not pathways from point A to B, but the purpose of the journey.
The numerous adjacent functions of the commercial galleries exemplify the logic of multifunctionality: exhibition and conference centres, hotels, restaurants… Since the 1950s, galleries have related services. The first Gallery Louise, under the slogan "A city at the heart of the city" [9], already arranged shops, restaurants, private clubs, exhibitions and reception hall, parking lots, offices, shop storage and fifty "American flats" and apartments [10]. Those related services induce indoor spaces to withdraw into itself, as independent islands that accommodate visitors for a long time. This latter logic has strengthened since the 1970s with the slow paths' externalisation along outdoor pedestrian areas and another sidewalk extension. The Gallery Toison d'Or has been as a result transformed into a dead-end passage in the late 2000s. The length and continuity of the galleries became, notably with the third extension of the Louise Galleries [11], an argument for commercial attractiveness, even if it no longer constitutes a passage as such. One should go for a promenade but, above all, stay in this third extension.
The second logic that lets me define commercial galleries more as destination spaces than passages is the logic of fast mobility accessibility. Galleries are located next to pre-metro, expressways, tunnels and parking. The indoor and covered connections to those access means are further improved by lifts and escalators to reach destinations effortlessly. Parking issue is a key point in the development of each gallery. In the case of the Gallery Toison d'Or, the tunnelling of the pre-metro will allow the construction of access ramps for the underground parking in both directions of the Petite Ceinture highway. Everything guarantees ease, comfort and smoothness in the intermodal connection to the roadscape.
Third, the setting of an ambiance invites to flânerie and deceleration. On the one hand, the density of the public may alter the visibility of the passer-by and question the fluidity of build space. On the other hand, commercial galleries are specifically designed for slow paths in terms of materiality and dimension, and through some spatial configurations. The materials and the light create a calm atmosphere, a neutral environment. The atmosphere is comfortable, muffled and quiet. The standard musical background covers any noise.
Those complexes concentrate outside the urban fabric urban functions that prior participated in urbanity. The setting of an ambiance inside these complexes reproduces the reassuring setting of a traditional urban scenography. The model of the city -with arteries, small squares, terraces and stalls -is "recovered, absorbed, and, more importantly scriptwritten, planned and managed" [12]. It creates fragments of security city and managerial city. The security city guarantees physical safety and encounters with socially close individuals in order to avoid conflicts with heterogeneous thoughts and groups. Following the communitybased American example, it constitutes a "segmented city whose fragments have ceased to communicate" [12]. The managerial city relies on this segmentation to constitute "'communities' of consumers", target groups of commercial and spatial strategies [12]. Even if galleries seem to be open spaces for all, guardians, products adapted to the middle class' tastes and budgets, and more importantly, architecture guarantees the exclusion of poor people [13]. The ambiance controls and conditions both the material (air, light…) and the people. It transforms the urban flâneur and the passer-by in consumers [14].
The linear spatial structuration that imitates the traditional city centre is made of streets and squares. The latter ones are by nature sedentary places: rest area, exhibition area, reception, food court. The first give access to shops. Shop windows must be given all attention. "Paths are 'quaint', short, broken, avoiding tunnelling effect" [15] (that is to say the "effect of centration, slide and anticipation of sight" [1]). The design of the galleries is indeed based on the latest technical and scientific progress to make pedestrians decelerate, to invite them to a slow and "flowing" movement from one side of the gallery to the other. Sociological and psycho-commercial analysis were carried out to determine the best dimension of the hall so that the passer-by will not "be absorbed in a fast flow" [16]. The deceleration operates through the distraction that procure the environment, inviting to a sensory intensity within the modern and luxurious ambiance made of noble materials (blue stone, marble, mirror, vegetation). Those materials create rhythmic lateral appeals for sight along the path. Large halls with shop windows dilate the visual field, appeal lateral view and offer opportunities for breaks.
Furthermore, escalators generate spatial disorientation and confusion that tend to capture the visitor. "Escalator acts as a strategic tool to raise the complex and uncontrolled nature of flows" [17]. This confusion is backed by the trends of boundaries dematerialisation [4]. Visual field of galleries -flowing space with unclear limits -is characterised by crossfading and overprint. It requires passers-by to find other visual clues than that of a well-defined perspective space with clear boundaries and clear figure/ground ratio (as traditional public space made of full and empty spaces). The systematic use of glass shapes other boundaries. Either its transparency creates a visual dilation of public space as semi-public spaces behind the shop windows are made accessible for sight. Either its partial reflection back at passersby deconstructs the space and articulates the two distinct spatial units by only suggesting spatial depth with a filtering effect. The escalators that link the different storeys allow an intimate relation with the built environment. The created space operates as a complex and progressive stretching deformation, connecting apparently incompatible spaces to create a large indoor landscape perceived in one continuous movement [17]. In their evolution, galleries evolve toward a more horizontal, "landscaped" spatial structuration (see the redesign of Toison d'Or Gallery in the late 2000s) that dilate the space even more.
On top of shop windows, some spatial configurations also offer opportunities for breaks: the show grip effect of the sky through roof windows, or of a diving view on other passersby's overexposed activity. In the first configuration, the recurring sky contemplation behaviours are loopholes from feelings of lockdown as there is no visual horizon. "The sight compensates the impossibility for the body to go out." [1] This behaviour is a simultaneous stop of the step and the eye on the aerial landscape. After attracting the passers-by further in the gallery (see 2.2), the natural lighting captures them inside. In the second one, it's the "overexposure" [4] of the passer-by that invites for contemplation from a privileged perspective. The overexposure is caused by the spatio-visual dispositif of architecture itself: stylisation of build shapes and contrast with the light floor offering panoramic views. The indoor belvederes - balcony and stairs at the connection of the Porte Louise with Espace Louise and the double height of the restaurant area of Espace Louise - create a grip effect that captures the observer. It also creates tempting views from one level to the other.

Acceleration of slow mobility
Within commercial galleries, the logics of slow mobility deceleration create a tension with dispositifs that favour mobility of pedestrians. Those dispositifs, unfolding the notion of comfort, articulate different traditional, enduring logics of slow mobility acceleration: securement, spatial and qualitative continuities. According to Carmen Hass-Klau, the predecessors of both pedestrian areas and malls protected pedestrians in 19 th century European congested city centres both from traffic and bad weather [18].
The logic of securement of slow paths expresses itself through the strong spatial segregation. It is materialised in externalised paths through commercial galleries and, later, also in external enlarges sidewalk protected by huge planter boxes from expressways (see Toison d'Or Avenue). In that way, it carries on the undertaking of the 19 th century galleries that attempted to separate pedestrian and wheeled traffic. Twentie th century galleries are indeed still described as passages "safe from mechanical traffic" [19].
The logic of spatial continuity, through commercial galleries, solves the congestion problems at small scale: "the continuous congestion of sidewalks" caused by pedestrian crossing, traffic light and bus stop [20]. To build galleries is to construct "covered passages" that enable shortcuts in the urban fabric and avoidance of sidewalk congestion. It also connects commercial zones ("Deux Portes") or different neighbourhoods. The Agora Gallery is a "direct connection between the different attractive centres" [16] between the touristic and patrimonial city centre and the institutions neighbourhood. The indoor spaces of commercial galleries are that way fully considered as mobility infrastructure. It is not only an "analogous city" that supersedes the contemporary city with a simulacrum of the city with no connection to the urban surroundings [14,21]. It still reproduces the linear spatial structuration of the city centre. Galleries are based on a compilation of "streets", "squares" with fountains and benches. Architectural dimensions, transparency, even the planting, contribute to giving indoor spaces a public character. So does also the work of art: the sculpture in Porte Louise distract the visitor from commercial aspects of the venue. The "public space" model trivialise the gallery, make it become familiar and common [15], and therefore used as what it pretends to be: mobility infrastructure. The use of the street-related vocabulary ("roundabout", "artery", "square", "forecourt") supports this conceptual - and semantic - transfer and extension of public space into the built environment.
The notion of spatial continuity is closely linked to that of comfort. The logic of qualitative continuity relates both to functionality and aestheticism. Besides protecting from "traffic trepidation", galleries keep pedestrians "safe from bad weather conditions" [22]. First, this is made by climatic comfort: heating system, artificial and natural lighting, covered passages that allow "to go for a covered stroll (se rendre en promenade et à couvert)" [23]. Second, by specific and high standard design: "both measured and luxurious modernism" [10]. The design of commercial galleries helps to keep passer-by moving. Ironically, escalators also provide a way to speed up movement because of its mechanics of movement. The dimension of indoor squares also challenges the possibility to stay without consuming.
At a sensitive level, the demand to circulate also operates through slick and slippery quality of finishing materials. At the entrance of the Toison d'Or Gallery or at the connection between the Porte Louise and Espace Louise galleries, the passer-by is invited to progress into the building by an "effect of luminous drive" (entraînement du lumineux) [1]. An emerging and prevailing luminous occurrence as a roof window attracts the gaze and drive the full body. The transition from artificial to natural lighting is normally perceived as a way out but when it isn't, it projects the body forwards into the gallery. An accelerant "effect of sight centration, slide and anticipation" also operates in spaces designed with a strong directionality and a narrow visual field framed by opaque surfaces as corridors. "The sight can only escape by focussing on the exit way, the steps only repeat what has already been done by the sight." [1] For instance, this sensory-motor effect operates in some connection spaces as the narrow corridor linking the first Gallery Louise to Stéphanie Square between 1955 and 1963.

Conclusion
Unlike other urban spaces where walking is considered as a residual mobility vanishing with the rate of progress, commercial galleries constitute spaces where subsists a "right to speed" by walking, to efficient (small scale) slow mobility paths. This demand to circulate also relates to the definition of walking as a resource for the market (24). Property value and rental value are directly linked to the density of pedestrian flows. Therefore, material and regulatory dispositifs mostly aim at regulating walking by eliminating obstacles to traffic. This paradoxical demand to circulate and to stay is then due to the function itself of the gallery: it aims at attracting loads of people while preventing congestion threats that crowd generates. It facilitates movement to better keep consumers captive, to let them "legitimately stay, that is to say to consume" [15]. In that sense, commercial galleries prefigure the design of contemporary pedestrian areas, where walking is enforced and naturalised as the only modality for accessing this public space [24]. Historical European city centres will implement designs and forms of "living together" developed by their simulacrum [14,25].
To conclude, I wanted to draw attention to the relevance of iconographic archives for academic research on ambiance. The analysis reveals how the paradoxical demand to circulate and to stay is supplemented by different sensory-motor effects appearing in iconographic archives about those galleries. However, the analysis still relies to a large extent on other -discursive -sources. Iconographic archives are not sufficient. Dealing with iconographic archives also only take into account the visual dimension of modernist ambiance, neglecting the other senses: hearing, touch, smell and taste that have a greater importance in the concept of ambiance. Iconographic archives nevertheless confirm the paradoxical status of the commercial gallery of the latter half of the 20 th century as a space of (functional) slow mobility and as a space of destination. The research gives that way a better understanding of the tension evolution, in mobility infrastructure development, between the fast and the slow mobility imaginary in Brussels.