374 W. J. Taylor on Meteoric Iron from Mexico, 



For the forcing back of the mass if into the boiler: 



(42.) W±=-Ma( Pl - Po ). 

 The whole work is therefore : 



(43.) Wz^m 2 r 2 -m z r 3+ (M+t*)c(T 2 - T z )] + m 2 u 2 (p\ -p 2 ) 



The masses m 2 and ra 3 which occur herein may be found 

 from equations (xra) and (vn), in which it is only necessary to 

 substitute in the first the value p" 0 in the place of p 0 to change 

 in corresponding manner the quantities T 0 , r Q and u 01 and to in- 

 troduce in the last the sum M+p in the place of M. I will not, 

 however, here completely execute the elimination of the two 

 quantities m 2 and m 3 which is possible by these equations, but 

 will only substitute its value for one of them m 2 , because it is 

 more advantageous for calculation to consider the equation so 

 obtained together with the two already determined. The system 

 of equations which serves to determine the work of the steam 

 engine, is therefore in its most general form : 



TF-^Kr i - m 3 r 3 +Mc ( T t - T z ) 



r" 0 -t*c(T s - T" Q ) ]+ m 3 u 3 (p, ~p' 0 ) 



J +V 0 t*"o(P'o ~P"o)- Ma (P'o -Po)- 

 XlY ' I m 2 [r 2 +Au 2 (p\-p 2 )=m 1 r 1 +Mc(T 1 -T 2 ) W \^ 

 +An 0 u» 0 {p" 1 -p\)+AM<j(p 1 ~p> 1 ) 



(To be concluded.) 



Art. XXIX. — Examination of the Meteoric Iron from Xiquipilco, 

 Mexico ; by W. J. Taylor * 



The meteoric iron from Xiquipilco, Mexico, appears to have 

 been first mentioned in the Gazeta de Mexico in 1784. It is 

 stated there that small pieces of native iron, from a few ounces 

 to fifty pounds in weight were very numerous, which were sought 

 for by the Indians after heavy rains, who used them for manu- 

 facturing agricultural implements. 



In a dissertation on metallic meteorites by Prof. W. S. Clark, 

 the following notices of its literature are given : — Ann. des Mines 

 Ser. 1, t. 2, p. 337. Gazeta de Mexico, 1784-5, vol. i., pp. 146, 

 200. Klaproth Beitrage zur chemischen Kenntniss der Mineral 

 Korper, B. 4, s. 101. Sonnenschmit, Beschriebung der vorzug- 



* From the Proceed. Acad. Nat. Sci. of Philadelphia, vol. viii, No. 3. 



