Polytechnic Association. 749 



the predominance of such salts in the serum of the blood which only 

 physically dissolve carbonic acid, and do not allow the normal quantity 

 of that gas to be exhaled, and thus impede the access of oxygen. 

 Medical men should bear in mind that if given alone, these extracts, 

 and likewise beef tea, are no nutriment, and only tend to keep the 

 convalescent weak, being thus ill fed, or, rather, not fed at all. These 

 conclusions are substantially those entertained by Liebig and many 

 other investigators in the same iield. 



Dr. P. H. Yan der Weyde — The extracts of meat, brought from 

 Texas, do pretty well for making a hasty plate of soup, but have not 

 the power of the meat. The excess of potash is injurious. We want 

 sodium and not potassium. For instance, we use the sulphate of 

 sodium, or Glauber's salts, but give the sulphate of potassium to 

 horses. The iodide of potassium produces eruptions, and the iodide 

 of sodium does not. While it is even asserted that all the potash, 

 compounds are poisonous, we need the chloride of sodium, or com- 

 mon salt, in the system ; and if we do not supply it, it is recomposed 

 in the system. 



The President — Potash seems to play an important part in vege- 

 table life and sodium salts in animal life. 



Dr. Richards — Potatoes, which are highly charged with potassium, 

 are especially recommended to sailors for scurvy. Potash is a valuable 

 medicine. In a recent experiment, a very small amount of potash 

 injected into the veins, stopped the motion of the heart and killed 

 the animal. An equal quantity of soda had no effect at all. Potash, 

 is used as a medicine, and so are arsenic and mercury, although they 

 are deadly poisons. 



Compound Propeller Pump. 



Mr. Thomas Shaw, of Philadelphia, exhibited and explained a 

 model of the compound propeller pump, exhibited at the Fair of the 

 American Institute. It has first a revolving propeller blade, which 

 lifts and rotates the water ; then a stationary propeller blade, with 

 the angle reversed, to counteract the rotary tendency ; then another 

 revolving blade, a short distance above it, and a stationary blade 

 immediately above that, and so on to the top of the tube. The maxi- 

 mum pressure produced by each pair of blades is three pounds to the 

 square inch. 



Mr. T. D. Stetson — What is the gain in duplicating the blades all 

 the way up, over putting them all at the bottom ? 



Mr. T. Shaw — You can put them all at one end, or scatter them 



