. In 1837 Cooke leased a shop at 50 Stonegate,
York, with his wife running the shop and Cooke's workshop occupying the rear where he made and repaired whatever instruments were needed. He made a
screw-cutting lathe for his own use. A notable instrument made at this time was a 4.5 inch
equatorial refracting telescope. Cooke himself made the whole instrument including the
optical elements at a time when most instrument makers specialised in making either the optical or mechanical components. The 1851
census shows that Cooke employed four men and an apprentice. In 1855 Cooke exhibited at the
Exposition Universelle in Paris and won a First Class Medal for a 7.5 inch equatorial refractor. By 1855 Thomas Cooke had built a factory at
Bishophill in York. In 1864 Cooke undertook his first order for surveying equipment when he built 16
theodolites to be sent to India. On arrival they were found to be very well made except that the circle division was faulty. They were returned to York and redivided. By 1870 The
Survey of India used Cooke levels for the primary survey in preference to
Troughton & Simms products as they considered them to be superior. Following the death of Cooke in 1868, the business was continued by his sons. The firm built the clock face on the
Darlington clock tower. Cooke & Sons also provided a 12 inch theodolite for the construction of the
Forth Railway Bridge. Observatory domes were also made using
papier-maché including in 1883 one for
Greenwich Observatory. In 1892
Dennis Taylor, working to reduce
chromatic aberration, invented a three element lens design incorporating a new
Schott glass element. This design was called a 'photo-visual' design and used for both visual and photographic astronomy. Taylor became Optical Manager at the firm in 1893. Six lightweight theodolites were made for Scott's ill-fated
Terra Nova Expedition of 1910-1913. Dennis Taylor modified his three element lens design for photographic purposes, patenting his work in 1905 and 1906. This 'Cooke Triplet' lens design was an improvement on most camera lenses of the time though it was in competition with the 1902 Zeiss
Tessar design. In 1904 Taylor discovered that a tarnished surface layer could reduce reflections from glass surfaces. Although this effect had been discovered by
Lord Rayleigh in 1886 the use of lens coatings was not widely known. With war looming the firm began to work with
Arthur Pollen on his 'Aim Correction' system for improving the accuracy of naval gunnery. Cooke & Sons supplied the optical components for the system which consisted of a gyroscopically stabilised rangefinder where successive readings of a moving target were mechanically integrated to give a prediction of range and bearing. In the event the
British Admiralty for the most part chose the simpler and cheaper
Dreyer predictor. In 1914, a new factory was built in Bishophill. ==See also==