K. MECHANICS AND ENGINEEKING. 389 



K. MECHANICS AND ENGINEERING. . 



PRINCIPLE OF " LEAST ACTION IX NATURE." 



In a course of lectures delivered before the Royal Institu- 

 tion of Great Britain by Rev. Samuel Haughton, of Dublin, 

 he attempts to prove that in every arrangement of bone, 

 muscle, joints, and parts of animals, the relations must be such 

 as to produce a given result with the least possible expendi- 

 ture of labor, and that this principle of " least action in na- 

 ture" is a guiding one, and can be shown to exist not merely 

 in the movements of the planetary and stellar bodies, but 

 also, and illustrated as well, in all physical phenomena, as in 

 those of an organic nature. As is well known to manv of 

 our readers, Professor Haughton is one of the highest author- 

 ities on specical and animal mechanics, and it is in this branch 

 of research that he endeavors to prove the existence of the 

 law in question. 20 A, May 27, 597. 



Fletcher's rhtsimetre. 



Mr. Fletcher communicates to the British Association an 

 instrument which he calls the Rhysimetre, intended to indi- 

 cate the velocity of flowing liquids, and measuring the speed 

 of ships through the water. The principle resembles that of 

 the anemometer of Mr. Fletcher, by which he is able to meas- 

 ure the speed of hot air, flame, and smoke. In both instru- 

 ments the impact force of the current, and also its tendency 

 to induce a current parallel with itself, are measured, and be- 

 come indicators of the force and velocity of the stream. A 

 modification of the apparatus is used in measuring the speed 

 of ships, the indicator, in size and appearance resembling a 

 barometer, being placed in the captain's cabin. The instru- 

 ment can be made self-registering, marking on a sheet of pa- 

 per the speed obtained at any instant of time. It is said 

 that it has already been introduced on board some of the 

 larger steamers plying between England and America, and 

 has proved of great value, superseding entirely the crude 

 process of " throwing the log," as it shows at any moment 

 the exact speed of the ship. 18 A, August 18, 531. 



