These are instantaneous sketches taken directly from nature, here on the coast, in the French countryside, and in the mountains of Picos de Europa. Haes was a moving force in the transformation of landscape painting, bringing a completely new concept of the interpretation of Nature, with a realism that was sensitive to all elements. In all his landscapes, Haes very exactly captures the physical aspects of each of the elements he depicts. In some, energetic, impasto brushstrokes are used to reproduce the rough character of the rocks, while the clouds are rendered with more diluted paint. Thus, Haes builds the landscapes with paint itself. The cold and humid atmospheres are captures with very subtle coats of paint that envelope and hid the mountains. This technique of subtle and transparent brushstrokes is also used with other darker tonalities to show urban pollution. In his studio in Madrid, this extraordinarily well-trained painter accumulated a huge number of small sketches made over the course of his trips through the geography of Europe. When he died, his collection was kept by his disciples, who donated it to the Museum of Modern Art in 1889.