Altogether Miss Leavitt has added 1,500 new variables to the already rapidly growing list.
It may be asked, why it is necessary, or even desirable, to go on indefinitely with the discovery of new variables. The answer is that, aside from the value of adding any new fact about the universe to the sum of human knowledge, the problem is now so well advanced that it seems unwise not to render the search complete for the whole sky. A serious international attempt is about to be made, for the first time, to investigate systematically all the leading problems concerned in the construction of the universe, so that a scientific cosmogony may be possible. It will be of value in this greatest of all problems to find
the discussion of the variable stars reasonably complete for the whole sky. At the Harvard Observatory, where variable stars have been given serious attention during more than twenty years, a new catalogue, compiled by Miss Cannon, is in course of publication, which contains reference to about 1,850 variables. This does not include the variable stars in the Magellanic Clouds. Also, a committee of the Astronomische-Gesellschaft. consisting of the well-known astronomers, Dunér, Müller, Oudermans and Hartwig, have in hand the preparation of a catalogue, which will be an extension of the former catalogues of Chandler.
The work of discovery, however arduous, is but a small part of the whole problem of the variable stars. Long series of observations are necessary, in order to learn the amount, duration and rapidity of the light-changes, or, in other words, to determine the light-curve.
