752 Transactions of the American Institute. 



there is the friction of the blades. "With regard to that it does not 

 appear to make any difference whether the work is done by one pair 

 or by many pairs ; for, in the latter case, although the friction of each 

 will be less, that mnst be multiplied by the number, which will bring 

 about the same result. Nor does it appear to matter much, in this 

 respect, whether the blades are distributed through the length of the 

 pipe, or accumulated at one point. 



But, in the third place, there is friction upon the pipe, and, in 

 respect to that, it does matter where the blades are placed. The trie, 

 tion upon the pipe varies with the pressure. If the blades are dis- 

 tributed along the length of the pipe, each lifting the water only two 

 or three feet, and then another taking it, there is a gentle pressure 

 the whole length of the pipe ; as Mr. Shaw tells us was actually 

 observed on boring the holes in the pipe at the Novelty Works. But, 

 on the other hand, if the water is lifted the whole distance by one 

 pair of blades, or by a number of blades placed together at the bottom, 

 assuming that, with the exception of this element of friction, the 

 effect would be the same, it is evident that the pressure upon the pipe 

 would be very great ; for it would be, at each point in the pipe, the 

 amount due to the height of the water from that point to the top of 

 the pipe. As the friction would be correspondingly great, I should 

 judge that the whole amount of ^friction of the pump would be at 

 least ten per cent greater from placing the blades at the bottom of the 

 pipe. 



The President — This subject will be again taken up, after we have 

 a report on the further investigation which is to be made. 



Adjourned. 



January 12, 1872. 



Prof. S. D. Tillmajst, in the chair ; Robert Weir, Esq. , Secretary. 

 Dr. Lewis Feuchtwanger read the following paper : 



The Potash, Soda and Maonesia Compounds in the Rook-salt 

 Deposits of Stassfurt. 



[Illustrated by many specimens of minerals.] 



The most interesting and important mineral deposits of recent dis- 

 covery are those of the salt works at Stassfurt, in Prussia. They 

 have produced quite a revolution in domestic economy, giving to the 

 chloride of potassium, which is found at the depth of a thousand feet, 

 a great commercial value. This, with other peculiar salts, was dis- 



