marked turning points in their stylistic evolution: Magritte's Voice of Space (La Voix des airs) is an example of this process, where three large spheres representing bells hang above a landscape. Another Surrealist landscape from this same year is Yves Tanguy's Promontory Palace (Palais promontoire), with its molten forms and liquid shapes. Liquid shapes became the trademark of Dalí, particularly in his The Persistence of Memory, which features the image of watches that sag as if they were melting. The characteristics of this style—a combination of the depictive, the abstract, and the psychological—came to stand for the alienation which many people felt in the modern period, combined with the sense of reaching more deeply into the psyche, to be "made whole with one's individuality". Between 1930 and 1933, the Surrealist Group in Paris issued the periodical Le Surréalisme au service de la révolution as the successor of La Révolution surréaliste. From 1936 through 1938 Wolfgang Paalen, Gordon Onslow Ford, and Roberto Matta joined the group. Paalen contributed Fumage and Onslow Ford Coulage as new pictorial automatic techniques. Long after personal, political and professional tensions fragmented the Surrealist group, Magritte and Dalí continued to define a visual program in the arts. This program reached beyond painting, to encompass photography as well, as can be seen from a Man Ray self-portrait, whose use of assemblage influenced Robert Rauschenberg's collage boxes. During the 1930s Peggy Guggenheim, an important American art collector, married Max Ernst and began promoting work by other Surrealists such as Yves Tanguy and the British artist John Tunnard. Major exhibitions in the 1930s 1936 – London International Surrealist Exhibition is organised in London by the art historian Herbert Read, with an introduction by André Breton. 1936 – Museum of Modern Art in New York shows the exhibition Fantastic Art, Dada and Surrealism. 1938 – A new Exposition Internationale du Surréalisme was held at the Beaux-arts Gallery, Paris, with more than 60 artists from different countries, and showed around 300 paintings, objects, collages, photographs and installations. The Surrealists wanted to create an exhibition which in itself would be a creative act and called on Marcel Duchamp, Wolfgang Paalen, Man Ray and others to do so. At the exhibition's entrance Salvador Dalí placed his Rainy Taxi (an old taxi rigged to produce a steady drizzle of water down the inside of the windows, and a shark-headed creature in the driver's seat and