Cowley Automatic Level in green enamel.
A Haldens of Manchester brochure (undated) describes the level thus:
“PATENTED SELF LEVELLING DESIGN
The “Cowley” levels automatically. An off vertical position of the tripod does not affect the “Cowley’s” operation. The unique but simple mechanism automatically compensates for the tilt of the instrument housing, thus assuring a true horizontal line of sight without loss of time for setting up or adjustment.
Far more precise than the use of string, wire, straight edge or spirit level – much faster than a telescopic level – the “Cowley” is the perfect low-cost instrument for all levelling purposes. It combines simplicity with speed and accuracy – skill, training and experience are not necessary. The “Cowley” is always ready for use, involves no setting-up, and requires no adjustment. The patented optical mechanical system is fully enclosed in a sturdy housing that provides complete protection. It is light, compact and equally practical for short and long distances. The “Cowley” is moderate in price and saves time and money on every job.
LIGHT, STURDY, POCKET-SIZE
The “Cowley” is about the same size as a small camera. 4¾ x 5½ x 2 inches. It weighs just 2⅔ lbs., and may be easily carried in the pocket. Even with tripod, target and staff the total weight is under 7 pounds – less than one-third the weight of conventional equipment. This feature of easy portability is an important advantage, particularly for out-of-doors use.
FOR LONG OR SHORT DISTANCES
The “Cowley” may be used with equal ease and accuracy for close or distant sighting – from 6 inches to 100 feet or more. While its precision is guaranteed to ¼ inch in 100 feet (with proportionally greater accuracy at shorter distances many critical tests have proved the “Cowley” to be more accurate than its guarantee provides. (Test records on request). The range can be doubled by means of the “Distance Target”.”
To see the Instruction Manual click https://ice-museum-scotland.hw.ac.uk/wp-content/uploads/cowley_instructions.pdf.
A working example of a Cowley level was later donated (see 2019/034).