DEDUCTIONS FROM THE TIDES. 35 



Harris does not claim that the demonstration of these is complete 

 or final, and he recognizes that much additional data will be required for 

 a full verification of the postulated systems and for completing the full 

 category of systems, but he believes that those announced correspond 

 fairly well with existing knowledge. Question has been raised as to whether 

 the phases of oscillation which he assigns to his systems are such as would 

 naturally arise from the forced waves. Question has also been raised as 

 to the adaptability of the oceanic segments to oscillate as postulated.' 

 Harris contributes a new map of cotidal lines for the world (fig. 3) in which 

 interpretation is conveniently combined with the observed data which 

 are also given separately in tables and in sectional charts. By comparison 

 of this cotidal map with previous charts, it will be seen that Harris's inter- 

 pretation departs rather markedly from that implied by the previous 

 cotidal charts. 



A significant feature of Harris's cotidal map is its amphidromic nodes, 

 centers of little or no tide about which the tidal wave swings in the course 

 of the twelve-lunar-hour period. Three of these amphidromic points are 

 located in the Pacific, one in the North Atlantic, and one in the Indian 

 Ocean (fig. 3). These points are associated with nodal lines that separate 

 the oscillating sections of the systems to which they are assigned. That 

 there should be such nodes of little or no tide in the heart of the great 

 oceans, where under the familiar mode of interpretation the tidal waves 

 should have their freest sweep and greatest strength, well expresses the 

 extent of Harris's interpretational departure. 



It appears then that, under the broad mantle of the postulate that the 

 tides are due to the attractions of the sun and moon, there are three special 

 or proximate views as to the immediate origin of the actual tides: (1) the 

 direct attraction of the tide-producing bodies on the water; (2) the effect 

 of stationary oscillations promoted by such direct attraction; and (3) the 

 to-and-fro tilting of the rock basins in which the water-bodies rest by 

 the tides of the lithosphere. The older view has always recognized the 

 supplementary effect of the natural oscillations of the water-bodies, but it 

 has never given them a prominent place nor quite that distinctive form 

 which has been assigned them by Harris. Since the cooperation of oscilla- 

 tions is independent of their source, any waves that may come from the 

 lithosphere are as available for building up systems of stationary oscilla- 

 tions as are those springing from direct attraction, since they are likely to 

 be timed quite as well. Harris's theory, or any theory of its kind, may 

 therefore find as good a working basis in tides derived from the lithosphere, 

 so far as these go, as in those formed by direct attraction. 



The vital question here is the bearing of the deductions from these three 

 points of view — assuming that each of them represents some truth — on 

 the rotational problem. Let us first consider this on the famihar assumption 

 that retardation is dependent on the position of the waves, assuming that 

 to produce retardation the wave on the moonward side must be in front 

 of that body pulling it forward and being itself in turn pulled backward 



' Nature, Sept. 4, 1902, p. 444; Apr. 23, 1903, p. 583; Jan. 11, 1906, p. 248; Feb. 22 

 1906, p. 388. 



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