Page:Proceedings of the Royal Society of London Vol 1.djvu/422

Rh and to have crossed the very ground where the armies of Cyaxares and Alyattes probably met. And if the order of events belonging to the reign of Gyaxares, as related by Herodotus, does not accord so exactly as might be wished with this determination, and cannot be entirely reconciled to their dates, Mr. Baily would attribute the confusion to the want of authentic documents at the time the history was written.

Although the author has employed in these calculations the secular variations of the moon’s mean longitude, mean anomaly, and mean distance from her node, as deduced from the formulae of Laplace, and given in the Tables Astronamiques, he expresses some doubts of the accuracy of these results; and his doubts are founded upon an eclipse recorded by Diodorus to have happened during the voyage of Agathocles from Syracuse to invade Africa, in the year 310 B. C., in which, when computed according to the present tables, the path of the moon’s shadow appears to have passed so much more south than Agathocles can be supposed to have been at that time, that the latitude of the moon would require to be at least 3° greater than our present tables make it.

These observations (if correct) would show the necessity of some alteration of the secular variation of the moon’s mean distance from her node; but this hypothesis, Mr. Baily observes, could not be reconciled with the eclipse mentioned by Herodotus; for by means of a corresponding correction, the eclipse of 610 would be found not to be total to any part of Asia Minor; and there is no other that could possibly be central and total within the utmost limits that are reconcilcable with any received systems of chronology.

It is now well known, says Mr. Farey, to many observers in geology, that the clay strata on which the metropolis is situated, extend north-eastward through Essex, Suffolk, and Norfolk, and are incumbent on the great chalk stratum, which reaches from the Isle of Wight to Flamhoro’-head; and that these, as well as many subjacent strata that are known, dip in general to the south-east, and basset out, or appear at the surface in succession, to any one travelling toward the N.W., until he has passed certain strata of lies, clay, and sand. Beneath these, says the author, are found marks of an immense stratum of red marl, which seems (to him) to have extended over all the remainder of the British islands. In this stratum are contained local strata of gypsum, rock salt, sand, micaceous gritstone, &c. : to this stratum also, according to the author, belong the great nodules of slate, green stone, sienite, basalt, &c. that form hills or mountains, intersected by mineral veins, in the western parts of the kingdom. In many parts, however, the red marl itself is no longer found; but instead of it various strata, subjacent to it, have