110 PROCEEDINGS OF THE ACADEMY OF 



July 7. 

 The President, Dr. Ruschenberger. in the chair. 

 Fifteen members present. 

 The death of Dr. Governeur Emerson was announced. 



Prof. Persifor Frazer, .Jr., made the folloTving remarks : 



I had the honor, at the hist meeting, of presenting to the Aca- 

 demy for its consideration, some attempts to reconcile the results 

 of the analyses of minerals 1)3' tlie best chemists with formulas, 

 which were constructed on the doctrine of quantivalence, i. e., the 

 known atom-saturating power of the elements. In my former 

 communication I endeavored to show that such a mixture of defi- 

 nite chemical compounds (generally cr3^stalli^ing in different sys- 

 tems) as was indicated b}^ the greater number of the old formulas 

 could not have those characteristic physical properties which serve 

 to distinguish homogeneous bodies from each other ; and above 

 all, that no mixture of two minerals crj-stallizing in different sys- 

 tems could produce a third cr\^stallizing in still another S3'stem. 

 I stated that there seemed to be onl3' two cases in which the for- 

 mation of minerals in this way is possible ; the one where one of 

 the compounds preponderates to such an extent that the resulting 

 mass is moulded according to its own morphological law ; aiid the 

 other where the resulting mass is not crystallized at all, but at 

 most cr3'stalline, 2. e., made up of minute cr3'stals or individuals 

 of each species, but simpl3- ^ggi'cgated together. 



That such is the explanation of man)' crystalline and cr3'pto- 

 crystalline rocks the microscope has sufficientl3' demonstrated, 

 and it would hardl3^ be going too far to sa3^, that, wherever an 

 amorphous mineral shows such a chemical constitution that its 

 elements cannot be brought into a single formula consistent with 

 what we alread3' know of the behavior of its anion and cathion 

 radicals, a strong probabilit3' exists that the mineral is simph^ a 

 mixture. 



On this hypothesis of the case the circumstance cannot fail to 

 demand explanation that the same mixtures in the same propor- 

 tions should so often occur with similar paragenesis ; and it is 

 not to be denied that this fact needs careful study'. 



But in man3' instances the cause of this uuiformit3', itself appa- 

 rently the result of chance, is to be traced to disintegration of a 

 previousl3' existing mineral into two or more others, or the partial 

 alteration of one mineral into another throughout its whole mass, 

 and by the action of outside forces. 



Thus chalcop3'rite might suffer partial decomposition into chal- 

 cocite and jna-ite, or into tenorite and hematite, or into all four of 



