Part of Samuel Morse's telegraph system was an automatic recorder of the dots and dashes of the code, inscribed on a paper tape by a pen moved by an electromagnet, with a clockwork mechanism advancing the paper. In 1848-1850 a system of such registers was used by John Locke to improve the precision of astronomical observations of stars, providing timing precision much greater than previous methods. This method was adopted by astronomers in other countries as well. William Thomson, 1st Baron Kelvin's syphon recorder of 1858 was a sensitive instrument that provided a permanent record of telegraph signals through long underwater telegraph cables. These recorders came to be referred to as pen registers, although this term later became part of law enforcement jargon referring to the use of such a register to record dialed telephone numbers.