largely responsible for assurance of the permanency of the dual state. Perplexing exceptions, however, remain, so that it is possible at present only to predicate the principal of most of the double canals but not of all. Leaving the exceptions out of account for the moment, we pass to those general characteristics which are intimately linked with what has just been said. Inasmuch as the act of getting into a state antedates the fact of being there, it is logical to let the description of the first precede. An account of the process of gemination may thus suitably come before that of its result. Flux, affecting the double canals in whole or part, is the cause of the apparent gemination. According as the flux is partitive or total is a single or a dual state produced. At the depth of its inconspicuousness the canal may cease to be visible at all; this occurs when both lines fade out. On the other hand, the one line may outfade the other, and we are presented with a seemingly single canal, at this its minimum showing. In such seasons of debility the one line may appear and the other not, or occasionally the other show and the one not, according to the air waves of the moment. It is at these times that the double simulates a single canal, and unless well seen and carefully watched might easily masquerade successfully as such. The Hiddekel in the depth of its dead season is peculiarly given to this alternately partitive presentation. As the flux comes on, one or both lines feel it. If one only we are likely to have a confused canal; if both, a difficult double. The strength of the lines increases until at last both attain their maximum, and the canal stands revealed an unmistakable pair, the two lines paralleling one another in appearance as in position.