Home › Authors › United States. Coast and Geodetic Survey. Magnetic Observatory, San Juan, P.R. 👤 United States. Coast and Geodetic Survey. Magnetic Observatory, San Juan, P.R. 1 book Books by United States. Coast and Geodetic Survey. Magnetic Observatory, San Juan, P.R. Magnetograms and hourly values Magnetograms and hourly values, San Juan, P. R 1950