Mechanical Science. 173 



accounted for by the stronger affinity of contact between the 

 iron and the water, than between the wood and the water, pro- 

 ducing an effect ef retardation in the lateral current, similar to 

 that produced by the rim in these experiments. Ultimately 

 he applied the contrivance of the rim in the construction 

 of the water-wheels for the manufactory before-mentioned ; 

 making them on the same principle as the edged disc. The 

 wheels were horizontal, revolving round a vertical axis, the 

 floats were placed in a canal as on vertical wheels, and were 

 guarded by rims, rising two inches from the surface. The pas- 

 sages for the water were of a pyramidal form, and passed 

 horizontally from the bottom of the reservoir containing the 

 water destined to move the wheel, forming tangents to the sur- 

 face of the wheel ; apertures were left at their under edge to 

 permit the water to escape, after having struck the floats. The 

 mouth of each passage was contained within the rims on the 

 floats, so that the whole effect of the moving water was exerted 

 on the plane opposed to it. 



In consequence of this arrangement, M. Morosi found the 

 quantity of water allotted him to be more than sufficient to 

 move the machines which were required : and a still better 

 proof of the value of the principle on which the wheels were 

 constructed afterwards occurred. Being called away after the 

 construction of the wheels, they were left in other hands, and 

 in some attempts to work them with a smaller quantity of 

 water, the rims were removed from the floats. In consequence 

 of this, all attempts to move them by tlie water were vain, and 

 as those who then managed them refused to believe that such 

 simple means as the rims could improve them, they were left 

 inactive for some time. When M. Morosi returned, his first 

 care was to restore the rims ; on which the wheels again worked 

 and have continued to work since. — Bibliothd^ue Universelle, 

 xii. p. 217. 



4. Improvement on Scissors. — A very valuable improvement 

 has been made on scissors. It is especially'so to those employed 

 /or delicate operations in surgery. The objection to the com- 



