Operational tests were conducted using simple visual receiving equipment to determine the consistency of the apparent times of arrival of Loran-C sky-wave signals at ranges from 1000 to 6000 km. Measurements were made from St. Thomas, Bermuda, and the Boston area, and comparison with ground-wave times of arrival were made using automatic receivers where available. Time-of-arrival consistency was observed to be within plus or minus 20 microns. The predictability of propagation delays, based on U.S. Naval Observatory estimated ground-wave delays, modified by sky-wave corrections published by the U. S. Naval Hydrographic Office, is discussed in connection with precise long-range clock synchronization using visual Loran-C equipment.