INTRODUCTION. 



varies the apparent Wheel-work, not 

 conflicting an eflential Difference. 



Thus this feeming Wheel-work 

 may in Effeft: be nothing more, 

 than an Apparatus of Horns or Arms 

 fimilar to that of the plumed Polypes^ 

 and analogous to the Horns invert- 

 ing the Head of the Barnacle \ which 

 it exerts for the fame Purpofe, form- 

 ing a Current as they do : Which 

 Circumftance, if it appears as pro- 

 bable to others as it does to me, 

 will ferve to clear up many Diffi- 

 culties, that feem to be the Confe- 

 quence of thefe microfcopical Phe- 

 nomena, if we fuppofe, with fome 

 Authors, the Wheel- work to be real, 

 by the Rotation of a detached Piece 

 of Mechanifm revolving upon its 

 Axis, and not apparent only by the 

 Play and A£tion of a Groupe of 

 Arms, 



Another Inftance of an Animal, 

 which is in Large, what fome mi- 

 crofcopical Animals are in Miniature, 

 is a Species of fmall ShelL fi(h, each 

 cf them fomething exceeding in Size 

 a Grain of ordinary coarfe Sand, 



which 



