Phillips on Mineralogy. 321 



primary importance, we shall briefly state its outlii\e, as, notwith- 

 standing our conviction that the work is in ihe hands of almost 

 every mineralogist, there may be one or two unacquainted with it; 

 and to such, if such there be, the statement 7mist be useful. 



The basis of the arrangement is chemical, and since certain 

 substances are found to occur in very large proportion in those 

 rocks which, geologically, are usually considered to be of the 

 oldest formation, the close alliance between geology and mine- 

 ralogy suggests the order, in which each class of minerals may be 

 taken. 



Some of the earths chiefly constitute tliose rocks which are esteemed to 

 be of the oldest formation ; while others do not enter into the composition 

 of rocks, being found only in the veins which traverse them ; these, there- 

 fore, (as veins are considered of posterior formation,) may be estimated as 

 being of later origin than the former. 



Of the alkalies and acids as mineral constituents, either combined with 

 the earths or with each other, the former claim the precedence, as entering 

 into the composition of the oldest rocks. 



Two or three of the metals occur in small quantity in the masses of some 

 of the earlier rocks ; but in general the metals are found in veins ; some in 

 veins traversing the older rocks, and rarely or never in those of a nf-wer 

 kind; others most abundantly, or only in those of newer formation. 



As rocks are constituted chiefly of earths, and metals are principally 

 found in veins, earthy minerals may be assumed to be of earlier origin than 

 the metalliferous. 



Proceeding according to this assumed relation in the respective 

 ages of the mineral elements, and beginning with the most simple, 

 and ending with the most compound substance, our author places 

 silica at the head of his list, " because it is estimated that silex 

 forms the largest proportion of the oldest and most abundant of 

 the primitive rocks ; and all earthy minerals, of which silex is the 

 largest ingredient, are arranged under that head ; beginning, che- 

 mically, with silex in its purest forms, and proceeding to such as 

 consist of that and another earth, as sile.x and alumine ; then to 

 those consisting of silex and lime, &c.; and afterwards to such mine- 

 rals as are chiefly constituted of three or more earths, terminating 

 with the most compound; and regarding the iron, manganese, &c., 

 involved in many of them only as accidental ingredients ;" because 

 they do not alter the external form, and internal structure of those 

 minerals. 



The other earthly minerals are proceeded with in like manner ; arbitrarily 

 selecting such as contain the rare earth glucine, and placing them under 

 that bead, except that the gadolinite, which also contains the still ffiore rare 

 earth yttria, is placed under the latter. 



Next after those minerals which consist only of one or more of the earths, 

 succeed those in which one or other of tlie alkalies is found ; to these, such 

 of tlie acids as occur in the concrete state ; then those minerals wliich are 

 primarily constituted of one or more earths and an acid ; and, after these, 

 those consisting of an alkali and an acid ; and, finally, the very few in which 

 an earth, an alkali, and an acid are combined together. 



Then follow those minerals (chiefly earthy) which have not been ana- 

 lyzed, or of' which but little is known. 



The native metals and metalliferous minerals succeed, arranged accord- 

 ing to the order of age and formation ; subordinately beginning with the 

 Y2 



