ELISHA MITCHELL SCIENTIFIC SOCIETY. 33 



value of one turn of the micrometer screw was determined by obser- 

 vations on Polaris when near its eastern elongation. 



The method of the U. S. Coast Survey was employed in the reduc- 

 tion of the observations, and from the data the latitude was com- 

 puted to be 35° 54' 18^^57 north. 



The record of observations and the computations will be preserved 

 by the Mitchell Society for future reference, should the determina- 

 tion of latitude ever be repeated. 



The latitude of this place was determined several years ago by Dr. 

 James Phillips to be 35° 54' 22", though there is no record of the 

 method employed or the position occupied by his instruments. 



While the Transit was accurately adjusted in the meridian, two 

 long stones were planted 175 feet apart, in the ends of which holes 

 were drilled and filled with melted lead, and in the lead were driven 

 small steel nails, marking the direction of geographic north and 

 south. This fixed meridian direction will be used for determining the 

 declination of the magnetic needle. 



THE MANUFACTURE OF -ACID" PHOSPHATE. 



W. B. PHILLIPS, PH. D. 



It is always interesting to notice the play between theory and prac- 

 tice. The student among his books and the workman with his tools 

 are one and the same person if the theory of the student is sustained 

 by the results of practical work. And in no department of industry 

 is the beautiful dove-tailing of what should be and what is more 

 fully illustrated than in the mauufacture of commercial manures. 

 Not that this coincidence of calculation and actual result is even 

 here perfect ; quite the contrary, in fact. But the illustration loses 

 nothing of its force by being along side of most things here, i. e., 

 far from perfect. The manufacture of fertilizers, which has grown 

 in 20 years from almost nothing to $30,000,000, can hardly be said 

 even now to be in a satisfactory condition. 



It is true that with certain crude phosphates our preconceived 

 notions of what they should yield on treatment with sulphuric 

 acid are borne out by the analyses of superphosphates made from 

 them. But I need hardly remind chemists and those acquainted 

 with the trade that there still remain large quantities of rich phos- 

 phates beyond the reach of the manufacturer's skill. It is only very 



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