Page:In the high heavens.djvu/79

 which has been established by a protracted series of observations, and treating it as if it were a constant. This method will be no longer admissible in astronomical work of the highest class. No doubt, from the sailor's point of view, an alteration in latitude which at most amounts to a shift of sixty feet, not a quarter, perhaps, of the length of his vessel, is immaterial. But in the more refined parts of astronomical work these discoveries can no longer be overlooked; indeed, Mr. Chandler has shown that many discrepancies by which astronomers have been baffled, can be removed when note is taken of the circumstance that the latitude of the observatory is in incessant alteration in accordance with the law which his labours have expounded. It will ere long be necessary, in every observatory where important work is being done, to apply each day the correction to the mean value of the latitude, in order to obtain the value appropriate for that day.

There are also other grounds of a somewhat profounder character on which the discoveries now made are eminently instructive. Those who are interested in the physics of our globe often discuss the question as to whether the internal heat, which the earth certainly possesses, is sufficiently intense to render the deep-seated portions of our globe more or less fluid. On the other hand, the effects of pressure, especially of such pressures as are experienced in the depths hundreds and thousands of miles below the surface, must go far to consolidate the materials to form what must resemble a rigid body. The question, therefore, arises, Is the earth to be regarded as a rigid mass, or is it not? The phenomena of the tides had already to some extent afforded information on this subject, and now Mr. Chandler's investigation adds much