ABSTRACT
Many attempts have been made from time to time to determine absolute personal equations; none, however, with conspicuous success, a weakness of some of the methods being the irregular oxidising action of galvanic contacts. There are other 'constants' connected with every separate planet and satellite, but these are generally discussed under the planets concerned. Refraction is on a different footing, and there seems little hope of obtaining perfect tables for low altitudes. The determination of astronomical constants perhaps hardly belongs to this chapter, but it will be convenient to refer to it here. It is quite possible that refraction tables which are satisfactory for one place will not be equally so for another, so that it might be well if more attention were devoted to this subject in fundamental observatories. The longitude observations made with instruments of this kind by Professor Albrecht and others are a strong testimony to the efficiency of the device.
