There is enough evidence for the significant weight that textbooks have nowdays in the science classroom, as a knowledge source of and as a means for teaching. In this paper a tool -sequential analysis-to search the teaching sequence of textbooks and the role of illustrations in such a sequence is described and applied. For that purpose a sample of Secondary level Physics and Chemistry textbooks was selected. The results lead to make clear the didactic profile of revised textbooks and their

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... ping in two classes, one connected with a more traditional conception on teaching-learning of Science and another connected with a more modern conception in relation with the Spanish Educational Reform. EL LIBRO DE TEXTO DE CIENCIAS EN EL PANORAMA DOCENTE ACTUAL La utilización de los libros de texto es a todas luces una de las principales vías de transmisión de la ciencia escolar en nuestras aulas. A pesar de los intentos hechos desde las administraciones educativas, desde el ámbito