Pocket Barometer by J Steward London
Silvered dial with original blued steel pointer signed ‘J.H.Steward Ltd, 406 Strand, London’ and numbered 7189.
The outer chapter ring is marked from 0- 4,000 feet and indicates the height above sea level. The inner ring is marked from 29 to 31 inches and indicates atmospheric pressure in inches of mercury,
To measure your height you rotate the outer chapter ring until the hand is aligned with the zero (assuming you are at sea level), then as you climb, the hand moves due to the fall in air pressure and you will be able to read off the height you have reached.
The word compensated indicates that this barometer adjusts the reading for changes in temperature, thereby giving a more accurate reading. C.1880
’Barometer makers and retailers’ by Edwin Banfield lists James Henry Steward as a mathematical and philosophical instrument maker and as an optician working from various addresses in London as follows:
406, Strand,1857-1900, 67 Strand 1867-68, 54 Cornhill 1867-92, 66 Strand 1869-88, 456 Strand 1879-88, 457 West Strand 1886-1900, 7 Gracechurch St 1893-1900. Prolific makers of all types of Barometers. Advertised as Maker of the Lord Bury telescope and of the Fitzroy barometers as in use at all railway termini and principle hotels in London.