Note 7 — CHAP. XXI. ON BALANCES AND PENDULUMS. (continued 2)
Reading edition
The variation produced in the height of the column of mercury (supposed to be 61/2 inches high) by an alteration of ± 16° in the temperature will be only ± 1/100 of an inch, or in other words, 1/100 of an inch will be the total variation from its mean state, by an alteration of 32° in the temperature. It is therefore probable that, in most cases of moderate alteration in the temperature, the centre only of the column of mercury is subject to elevation and depression, whilst the exterior parts remain attached to the sides of the glass vessel. It was with a view to obviate this inconvenience that Henry Browne, Esq. of Portland Place (I believe) first suggested the piece of floating glass.