352 On the Forms and States of Fluids [1831. 



112. The beautiful action thus produced at the limits of two 

 immiscible fluids, differing in density or some other circum- 

 stances, by which the denser was enabled most readily to 

 accommodate itself to rapid, regular and alternating displace- 

 ments of its support when that support was horizontal, sug- 

 gested an inquiry into the probable arrangement of the fluid 

 when the displacements were lateral or even superficial. 



113. On arranging the long plate (67. 81) verti- Fig. 27. 

 cally, so that the lower extremity dipped about one- 

 third of an inch into water, fig. 27, and causing it to 

 vibrate by applying the rod at x , or by tapping the 



plate with the finger, undulations of a peculiar cha- 

 racter were observed : those passing from the plate 

 towards the sides of the basin were scarcely visible 

 though the plate vibrated strongly, but in place of 

 such appeared others, in the production of which 

 the mechanical force of the vibrating plate exerted upon the 

 fluid was principally employed. These were apparently per- 

 manent elevations, at regular intervals, strongest at the plate, 

 projecting directly out from it over the surface of the water, 

 like the teeth of a coarse comb gradually diminishing in height, 

 and extending half or three-quarters of an inch in length. 

 These varied in commencing at the glass, or having intervening 

 ridges, or in height, or in length, or in number, or in breaking 

 up into violently agitated pimples and drops, &c. according as 

 the plate dipped more or less into the water, or vibrated more 

 or less violently, or subdivided whilst vibrating into parts, or 

 changed in other circumstances. But when the plate (sixteen 

 or seventeen inches long) dipped about one-sixth of an inch, 

 then four of these linear heaps occupied as nearly as possible 

 the same space as four heaps formed with the same plate in the 

 former way (83) and accompanied with the same sound. 



114. By fixing a wooden lath (69) perpendicularly down- 

 wards in a vice, plates of any size or form could be attached 

 to its lower end and immersed more or less in water ; and by 

 varying the immersion of the plate, or the length of the lath, 

 or the place against which the exciting rod (71) was applied, 

 the vibrations could be varied in rapidity to any extent. 



115. On using a piece of board at the extremity of the lath, 

 eight inches long and three inches deep, with pieces of tin 



