A SUMMER RAMBLE AMONG THE HEBRIDES. 223 



various forms, either reptile or ichthyic, Ganoid scales, of 

 nearly the same varieties of pattern as those in the Weald 

 of Morayshire, and the vertebrae and ribs, with the digital, 

 pelvic, and limb-bones, of saurians. It is not unworthy of 

 remark, that in none of the beds of this deposit did I find 

 any of the more characteristic shells of the system, Ammo- 

 nites, Belemnites, Gryphites, or Nautili 



I explored the shores of the island on to the Ru Stoir, and 

 thence to the Bay of Laig; but though I found detached 

 masses of the reptile bed occurring in abundance, indicating 

 that its place lay not far beyond the fall of ebb, in no other 

 locality save the one described did I find it laid bare. I 

 spent some time beside the Bay of Laig in re-examining the 

 musical sand, in the hope of determining the peculiarities on 

 which its sonorous qualities depended But I examined and 

 cross-examined it in vain. I merely succeeded in ascertain- 

 ing, in addition to my previous observations, that the loudest 

 sounds are elicited by drawing the hand slowly through the 

 incoherent mass, in a segment of a circle, at the full stretch 

 of the arm, and that the vibrations which produce them com- 

 municate a peculiar titillating sensation to the hand or foot 

 by which they are elicited, extending in the foot to the knee, 

 and in the hand to the elbow. When we pass the wet finger 

 along the edge of an ale-glass partially filled with water, we 

 see the vibrations thickly wrinkling the surface : the undu- 

 lations which, communicated to the air, produce sound, ren- 

 der themselves, when communicated to the water, visible to 

 the eye ; and the titillating feeling seems but a modification 

 of the same phenomenon acting on the nerves and fluids of 

 the leg or arm. It appears to be produced by the wrinklings 

 of the vibrations, if I may so speak, passing along sentient 

 channels. The sounds will ultimately be found dependent^ I 

 am of opinion, though I cannot yet explain the principle, on 

 the purely quartzose character of the sand, and the friction 



