learning geography, on which only a few prominent features of the country are laid down, and the learner is left to fill in the details as his knowledge advances.  Only in this case the details have already been filled in by the light of very imperfect knowledge, aided by a fertile imagination.  These we must obliterate if we would restore the possibility of a faithful delineation, and we must be careful, in future, to avoid a similar error.  We must put down nothing as certain which has not been conclusively shown to be so.

This last caution is specially needed at the present time, for, proud as we are of our advance in science, the amount of what is certainly known is probably very much less than we imagine.  A great deal that was received as certain a few years ago, is now considered to be doubtful, or even recognized as a mistake and abandoned.  This is especially the case with Astronomy, which seems to be almost in a state of revolution.  Dependent, as it is almost entirely, upon mechanical and optical aid, every improvement and discovery in these departments changes its position, bringing to light new facts, and modifying the aspect of those which were previously known.  The very basis of all astronomical calculations, the standard of time, is now no longer relied upon as invariable.  It is suspected of a change resulting from a gradual retardation in the rate of the earth’s rotation on its axis, produced by tidal friction.  When the binary stars were discovered, the discovery was hailed as a proof of the universal prevalence of the law of gravitation.  Later observations have thrown doubt upon that conclusion, as many pairs are known to exist, which, though they have what is termed a “common proper motion,” or are journeying through space together, have no relative motion, which they must show, if they were moving under the influence of their mutual attractions.  The supposed simplicity of the solar system has given place to extreme complexity.  A century ago, six planets, ten satellites, and a few comets, were supposed to constitute the whole retinue of the sun:  now, instead of this, we have two groups of four planets each, the individual members of each group closely resembling each other in all points within our knowledge, while in all these points the groups differ greatly.  Between these two groups lies a belt of very small planets, of which the 1st was discovered on the first day of the present century, and the 124th this year, and the number of known satellites has increased from 10 to 17.  Add to this the meteoric groups, and their suspected connexion with certain comets, and the perplexing questions suggested by the Solar Corona and the Zodiacal light, and it will be seen that our knowledge is in a transitional state; that with so many problems unsolved, any apparent contradiction to the sacred record will require a careful scrutiny to ascertain that the grounds on which it is brought forward are well established.