V. Description of the process of verifying thermometers at the Kew Observatory

It may be of interest to describe the method recently adopted at the Kew Observatory of verifying thermometers by comparison at different temperatures with a standard instrument, since a large proportion of the various thermometrical determinations made by English physicists are dependent for their accuracy upon that of the verifications at Kew. Many thousands of thermometers have already been verified by the apparatus about to be described. Up to the year 1875 the apparatus for this purpose at the Kew Observatory was of the rudest character.