204 ACTIVE TYPE OF STABILIZING GYRO. 



principle of this operation, using his own words, "consists in setting up a 

 secondan,^ and artificial resonance in order to annihilate the primary reso- 

 nance between waves and ship, it being on this fact that their operation is 

 based." 



The very grave question arises: — Is the basic proposition here enun- 

 ciated true? Is there any primary resonance between waves and ship or 

 really any approach to such a condition? This question was raised in this 

 discussion by one of the nestors of this art, and a fact was pointed out by 

 him which has been the basis of minute analysis on this side of the Atlantic 

 for some years past, namely, the oft-recurring cycles, or groups, universally 

 present in rolhng records. The facts thus brought out by Sir John I. 

 Thomycroft agree in the main with the results reached early in this investi- 

 gation by similar analysis on this side. These cycles are to be seen in any 

 rolling record, for instance, in Figs, i, 2, and 3, Plate 79, where it will be seen 

 that the rolling gradually increases to a maximimi and then decreases to a 

 mini muTn, whereupon another increase takes place, to be followed by another 

 decrease and so on. The sea is doing work upon the ship for a time and then, 

 in the words of Thomycroft, " it again undoes its work." In a very choppy 

 sea the recurrence of these cycles is very much accentuated; the groups 

 become smaller and less regular and sometimes more difficult to trace, but 

 still they are there. This can point to but one conclusion, namely, the 

 absence of anything that approaches true resonance between waves and ship. 

 It also argues strongly against any stabilizing device which is limited to 

 resonance phenomena only, be it primary or secondary resonance. Let us 

 examine these ciuT'es more minutely. It will be observed that at the end 

 of each cycle, before the next one starts, there is usually a change, more or 

 less definite, in the phase of the period where there is an apparent "fault" 

 in the regularity of the ciuves. The curves in Figs, i and 2, Plate 79, are 

 taken from a ver\' favorable sea, and when we examine curve 3, which is 

 taken from a less favorable sea, we see that these faults are more numerous 

 and occur with greater frequency. Inasmuch as this feature is characteristic 

 of all rolling of ships, how can it be successfully attacked by a device the 

 underlying principle of which depends upon periodicity and synchronism. 

 The water in the damping tanks can only create its damping movements 

 as a result of regular oscillations, and if this oscillation is irregular the 

 reactions fail to be propagated, and when the period changes what force 

 is there present to readjust the operation to the new condition? Of course 

 the answer to all of these questions is that tanks do not dampen under these 

 conditions. It is true that there are easy rolling conditions in an old sea 

 where they show to the greatest advantage and the damping action amoimts 



