sentences:  On his return to Spain he was entrusted with the building of the line from Pamplona to Zaragoza, and later became the chief engineer of a Spanish water company.Carvallo was the author of many dissertations printed in the "Comptes-Rendus do l'Académic des Sciences" and in many other scientific publications.Among his numerous contributions the most noteworthy were those on the piling up and solidification of embankments; on the formula of the maximum of stability and minimum of expense in public works; on the laws of oscillation of chain bridges, etc.