William F. Foshag (1894-1956) was a curator in the joined the US National Museum's Division of Mineralogy and Petrology. Foshag's research was primarily devoted to the study of the geology and mineralogy of Mexico. Between 1926 and 1941, Foshag made several collecting trips to Mexico under the auspices of the Smithsonian's Roebling Fund. While serving as a representative of the United States Geological Survey in its cooperative work with the Mexican government, during this time, Foshag was able to study the eruption of the Paricutin Volcano in 1943. He made subsequent visits to Paricutin in 1944 and 1945 to observe the volcano.
About 15 minutes after our arrival, a spot, about one meter across became more incandescent, changing from the glowing red of the lava cracks to a brilliant orange yellow, and began to work like leavening bread, and then to slowly flow. Slowly the moving area spread, and within five minutes the entire cliff, for the width of five meters had melted into a flow of brilliant orange.
--William Foshag while traversing the sides of Paricutin Volcano in Mexico in 1943.