Bidston Kelvin Machine
The Bidston Kelvin Machine is one of three types of Tide Predicting Machines (TPM) that have been used in the Bidston Observatory. This TPM-S14 was developed out of earlier type predicting machines, and made in 1925 by the firm of Kelvin, Bottomley and Baird of Glasgow, with Doodson taking great interest in its construction and suggesting modifications.
The other types are the Roberts Tide Predicting Machine (bought in 1929) and The Doodson-Légé Tide Predicting Machine (1950).
"Doodson wrote in an internal note that there was no difference in performance between the Bidston Kelvin and Roberts–Légé machines. He stated that for both “the total error of production of a tide does not differ by more than 0.05 ft (1.5 cm) and 1 min of time from calculations using the same harmonic constants, even for the largest ranges of tide”.[1]
"The Bidston Kelvin Machine may still be found at SHOM in Brest".[2]
