NATURAL PHILOSOPHY. 179 



were cooled, thus preventing the particles changing position in the act of 

 cooling. 



In 1849 a chemical laboratory was established at the United States Arsenal 

 at Pikesville, Md., for the purpose of analysing the cast iron employed hi the 

 manufacture of guns, and the charge of the experiments was committed to 

 Campbell Morfitt, Esq., as analytic chemist, with Professor Booth, of Philadel- 

 phia, as consulting chemist. The final report of these experiments was made 

 last year. The average specific gravity of the cold blast iron tested was 

 7.218, and the tensile strength was 29.219. The specific gravity of the hot 

 blast iron was 7.065 ; the tensile strength 19.640. The extraneous substances 

 combined with the iron were found to be allotropic carbon, combined carbon, 

 silicium, slag, &c. It would appear that the iron having the greatest amount 

 of combined carbon, with the least slag, was the best, and was found to be 

 made by the cold blast. The hot blast appears to drive off some of the 

 combining carbon, at the same tune leaving a greater quantity of allotropic 

 carbon, existing in a form analogous to graphite, or black lead, which is 

 injurious. 



The Report says : " The slag and allotropic carbon, being of a brittle nature, 

 and not united with the iron, coat the crystalline plates of metal, and diminish 

 their surface of contact, consequently it follows that the tensile strength of 

 the metal must decrease ha proportion to the increase of slag and allotropic 

 (uncombined) carbon." 



DOES THE MISSISSIPPI BUN UP HILL, OE DOWN HILL ? 



At a recent meeting of the American Academy, Prof. Lovering presented 

 the following communication, which originated hi a discussion, partially 

 carried on in the Common School Journal, as to the propriety of the question in 

 schools : " Does the Mississippi run up hill, or down hill ?" The article com- 

 mented on from the School Journal reads as follows : 



" The following egregious blunder, with the captivating title, ' Water run- 

 ning up Hill? is going the round of the public papers. ' Dr. Smith, in a recent 

 lecture on Geology, in New York, mentioned a curious circumstance connected 

 with the Mississippi River. It runs from north to south, and its mouth is 

 actually four miles higher than its source : a result due to the centrifugal motion 

 of the earth. Thirteen miles is the difference between the equatorial and polar 

 radius ; and the river, in two thousand miles, has to rise one third of this dis- 

 tance, it being the height of the equator above the pole. If this centrifugal force 

 were not continued, the rivers would flow back, and tJie ocean would overfloiu the 

 land} " 



This statement of Dr. Smith, said Prof. Lovering, is wholly correct, except 

 in the numerical details, in which Dr. Smith evidently did not aim at great 

 precision. But the writer in the Journal (who is understood to be President 

 Horace Mann) not only attacks the accuracy of these details, but assails the 

 mechanical principle which lies at the foundation of Dr. Smith's statement ; 

 saying, that " it would be difficult to compact a greater number of errors of 

 fact and of principle into one short paragraph, than are found in the above 

 quotation." The precise numbers involved in this question are of secondary 



