Effect upon the Ocean-tides of a Liquid Substratum, 213 

 and 



(ocos0<ft = f '-o/d* as-.' 



Jo Jo a a 



Therefore m, m f are proportional to the required integrals. 



Each slider might carry a train of wheels to record the 

 number of rotations ; or an electrical arrangement might be 

 made in which each wheel should complete a circuit at each 

 rotation and the number of contacts should be recorded. In 

 the latter case, as no distinction is preserved as to the direc- 

 tion in which the wheels revolve, it becomes necessary to have 

 four circuits, one for each cardinal point, with a recorder in 

 each, and to have one connected with each arm of the cross. 



A working model of the instrument above described was 

 exhibited at the Meeting, and was fitted with an electrical 

 arrangement such as I have mentioned. 



I have since discovered that the slits, sliders, and bar above 

 described may be replaced by a train of cogged wheels. (Fig. 4 

 represents the upper, and fig. 5 the under surface of the train.) 

 A bar turns in a horizontal plane about 0, and is kept in the 

 direction of the wind. This bar carries three wheels, H, K, L, 

 having the same axis. The length of the bar from one pivot 

 to the other is supposed to be an inch and a half. The wheels 

 H, K are rigidly connected; and L lies between them and turns 

 independently. H and K are 1 inch, and L is 3 inches in 

 diameter. L rolls on the inner edge of P, and H rolls on the 

 inner edge of Q, the diameters of P and Q being 6 and 4 

 inches respectively. Two wheels, M and N, whose diameters 

 are 2 inches, are carried by the wheel L, and have their centres 

 at the extremities of a diameter of L. M and N are in the 

 same plane as K, and are therefore touched by it. As the bar 

 rotates, M and N move without rotation, and their centres 

 move in straight lines passing through at right angles to one 

 another, and are at a fixed distance apart, and have the line 

 joining them bisected by the bar, which is the direction of the 

 wind. Hence M and N may be used to carry the wheels B, 

 (fig. 1) instead of their being carried by the sliders F and Gr. 



XXIV. On the Effect upon the Ocean-tides of a Liquid Sub- 

 stratum beneath the Earth's Crust, By the Rev. 0. Fisher, 

 M.A.,F.G.S* 

 (I) TN a work which I have lately published, entitled ' Physics 

 J- of the Earth's Crust ' f, I have maintained the theory 

 that the crust is thin, and floats in equilibrium upon a slightly 

 * Communicated by the Author, 

 t Macmillans, 1881. 



