There is perhaps no better test of a sound, practical astronomy, than to be able to determine truly the four cardinal points. A very simple and easy thing most persons would think it, but not so easy when brought to the test. The compass alone never can be depended on, except in a general way. The attempts of men to orient truly, even with the aid of science, have shown constant inaccuracy. It used to be thought a great matter to have churches and cathedrals built exactly east and west; but of all so intended scarcely one has been found that does not incline either to the north or the south of the line meant to be followed. It is the same even with buildings erected specially for astronomical purpose. Tycho Brahe's celebrated Uranibourg observatory is faulty in orientation to five minutes of a degree. The Greeks in the height of their glory could not find the cardinal points astronomically within eight degrees. But the builders of the Great Pyramid, out in the Lybian desert, with no guide or landmark but the naked stars, were able to orient their structure so exactly that the science of the wisest Athenian sages, eighteen hundred years afterwards, was seventy times, and the observatory of Uranibourg nearly four times, further out of the way than it is.One of the most curious and important problems of astronomy is the sun distance, atwhich men have labored so long and so earnestly without being able to solve it closer than within a limit of error embracing a million and a half of miles. That distance, however, is emphatically and definitely pronounced in the Great Pyramid, by its 10 and 9 of practical erection, as the even 10 times its own height, which is about the mean between the highest and lowest figures which the most recent observations have set down as the best results science has reached on this point.