1 74 Velocity of the Mississippi, 



19th. — A suite of minerals, consisting of petrifactions, 

 agates, jaspers and madrepores from Antigua, was present-- 

 ed by Capt. Redmond. 



Mr. Halsey reported on the Kalankoe Pinnata of La- 

 mark, which possesses the singular property of sending out 

 gemmae from the dentations of the leaf, which take root and 

 become new plants. 



3. Velocity of the Mississippi. 



To Professor Silliman. 



Sir, 



I take the liberty of calling your attention to a pas- 

 sage in a notice of Dr. Beck's Gazetteer, published in the 

 Journal of Science. Speaking of the Mississippi, the wri- 

 ter remarks, that " the velocity acquired in falling without 

 resistance through 5| inches, is about one foot and 

 a half a second, and would be the velocity of the river if 

 there were no resistance.'' The velocity was supposed to 

 be that which it acquires in running one mile. Another 

 passage contains a similar estimate. But here no regard 

 ie had to the continual acceleration of water, descending 

 without obstruction a series of inclined planes. Why is 

 the descent in one mile arbitrarily assumed as the datum 

 from which to estimate the velocity of the stream ? The 

 bottom of a river may be considered as consisting of a plane, 

 or series of planes. Now if these all incline the same way, 

 (which is not generally true,) and if the water descended 

 them without resistance, it is evident that its velocity at any 

 given place, would be equal to that acquired by a body in 

 falling perpendicularly through a space equal to the height 

 from which the water had descended. This velocity would, 

 however, be diminished by short tributary streams, in a 

 manner which I will not stop to explain. If freed from 

 all these causes of retardation, the Mississippi at its mouth 

 must have the amazing velocity acquired by water in fall^ 

 ing perpendicularly 1330 feet. 



But even admitting the correctness of the hydrodynamic 

 principles assumed by your correspondent, still is there not a 

 great mistake in the estimate ? For it is generally known that 

 a body falls without resistance about one foot in the first quar- 

 ter of a second ; in which case its mean velocity is 4 (t. per 



