The paper by Michel Meybeck presents a comprehensive study on the global chemical weathering of surficial rocks, focusing on the dissolved loads in rivers. The author combines water analyses from major rock types with their relative outcrop proportions to estimate the theoretical average composition of river waters. This approach, termed the Temperate Stream Model, is based on representative water analyses from unpolluted French watersheds and is compared to data from 16 major rock types. The breakdown of river loads into mineral and rock categories reveals that crystalline rocks contribute 11.6% of solutes from 33.9% of outcrop, while evaporites contribute 17.2% of the dissolved river load. Carbonate minerals in sedimentary rocks account for 50% of the total load, with bicarbonates primarily derived from soil and atmospheric CO₂. The study also estimates the chemical erosion rates for different rock types, with granite having a rate of 1.0 and shale having a rate of 2.5. The results confirm previous apportionment attempts and provide a detailed framework for understanding the global chemical weathering process.The paper by Michel Meybeck presents a comprehensive study on the global chemical weathering of surficial rocks, focusing on the dissolved loads in rivers. The author combines water analyses from major rock types with their relative outcrop proportions to estimate the theoretical average composition of river waters. This approach, termed the Temperate Stream Model, is based on representative water analyses from unpolluted French watersheds and is compared to data from 16 major rock types. The breakdown of river loads into mineral and rock categories reveals that crystalline rocks contribute 11.6% of solutes from 33.9% of outcrop, while evaporites contribute 17.2% of the dissolved river load. Carbonate minerals in sedimentary rocks account for 50% of the total load, with bicarbonates primarily derived from soil and atmospheric CO₂. The study also estimates the chemical erosion rates for different rock types, with granite having a rate of 1.0 and shale having a rate of 2.5. The results confirm previous apportionment attempts and provide a detailed framework for understanding the global chemical weathering process.