2 26 William E. Ford, 



CaCOs molecule is never present in these minerals in large 

 amount, no appreciable error will be introduced into the calcula- 

 tions if we take it as having the same specific gravity and molec- 

 ular volume as in calcite. Using therefore the specific gravities 

 for the dift'erent molecules as given on p. 215 the theoretical 

 specific gravities have been calculated for each analysis. 

 These together with the measured values are given in the 

 second half of Table II. Without making any attempt to criti- 

 cally examine the analyses the average difference between the 

 calculated and measured specific gravities is .048, or if the plus 

 and minus signs are considered it becomes -|-.oo8. It seems 



TABLE II 



Magnesite-Siderite and Siderite-Rhodochrosite Series 



* (i) Marchand and Scheerer, J. prakt. Chem., 50, 95. (2) Miinster, 

 Pogg. Ann., 65, 292, 1845. (3) Jentsch, N. Jb. Min., 535, 1853. (4) 

 Rumpf, Min. Mitt., 263, 1873. (5) Heddle, Min. of Scotland, i, 140. 

 (6) Bradley, previously unpublished. (7) Nikolajev, Min. Russlands, 7, 

 222, 1875. (8) Eisenhuth, Zs. Kr., 35, 594, 595, 599, 1901. (9) Fritsche, 

 Pogg. Ann., 70, 147, 1847. (10) Patera, Haidinger Ben, 2, 296, 1847. 

 (11) Weiss, J. preuss. geol. L. A., 113, 1885. (12) Manasse, Att. Soc. 

 Tosc, 22, 81, 1906. (13) Ford, previously unpublished. (14) Manasse, 

 Proc. Verb. Sc. Nat. Tosc, 15, 20, 1906. (15) Khuen, Handbuch Min. 

 Chem., I, 420. (16) Hutchinson, Min. Mag., 13, 209, 1903. (17) Diirr, 

 Zs. Kr., 47, 304, 1909. (18) Penfield, Am. J. Sc, 18, 50, 1879. (19) 

 Sandberger, N. Jb. Min., 2, 2>7, 1892. (20) Kunz, Am. J. Sc, 34, 477, 1887. 



