& 



310 Scientific Intelligence. 



Containing augite: diabase, augite-porphyry, melaphy 

 andesyte, feldspar-basalt (including doleryte and anamesyte), and 



tachytytc. — (</.) Containing ,ll,illny. n;,!, 1, ,■,,._(,. , t,,,t, ,„»,,< 



hypersthene: hypersthenyte. — (/.) Contolnhnj <!lvl n e: (serpentine) 

 "forellenstein." 



HI. Containing nephelite as the feldspar mineral. — Nephelin- 

 yte and nepheline-basalt. 



IV. Containing leucitk as the feldspar mineral. — Sanidin- 

 leucite rocks and leucite-basalt.* 



To understand this list it is necessary to have in mind some 



points in German usage connected with the naming of rocks. 



First, as to the affix, porphyry. It is not. as m -In ' ■ i"t v <l 



the name of a natural group or family of rocks, but, as the list 



shows, it is applied to rocks of various groups. It signifi. s n ally 



a f<: r h>i,';t;r ,-nrl.ty of some kind of rock. Felsite-porphyry is a 



telsite (typical p. u-phyry ) ; -rani; -porphyr\ is a pyi'- 



■ L by Zirkel to a Hi 



. between ordinary granite and fel- 



site. So in cases, not above particularized, diabase-porphyry is a 



porphyritic diabase, dioryte-porphyry, a porphyritic diorytc and 



soon. Again, the affix is used where th< 



nt some other mineral: thus. horiibiendc-per- 

 3 used by Zirkel, is a gray hornblendie rock in which the 

 seminated crystals arc hornblende ; and augite-porphyry, 

 one in wbicli the crystals arc augite. The science would be better 

 off without the word, except as used in the adjective form. 



Further: syenite of the Germans i> a nuk* consisting of horn- 

 blende and orthoclase without quartz, unlike the rock of Syene, 

 Egypt, which originated the name. Syenite containing quartz as 

 a prominent constituent is made a variety of granite — although 



- nearest relations to other hornblen 

 made the typical syenite, entitled, by usage elsewhere in the 

 above list, to the name quartz-syenite. 



Again, the names of some kinds of rocks are made to depend on 

 their geological age— an igneous rock if of Tertiary age 

 name, and : lorite WW 



augite along with more or less magnetite make together a rock 

 which is called basalt or >/.,/. ,-yt. u T.rti:,r\ ,„■ y u:.l 

 base if of earlier date. It is a method of naming which might 

 multiply names indefinitely, and whi.-h ha- u..ihi:u to commend 

 it. It is to be noted also rh.-a Zirkel uses the name basalt in place 

 of doleryte. Both ba-alt and di:iba>r ar. described a> often een- 

 tai iii _ viridite or a hydrous chloritic mineral. The term mela- 

 phyre is restricted to an amygdala 



always easily made, since the same dike or mass of rock is often 

 amygdaloidal in one small part and not through the rest of the 

 mass, and there is an indefinite gradation between such melaphyre 

 and the chloritic basalt. Peridot. ing olivine, 



is left as a variety of basalt. 



* The y in the last syllable of the names of many of the rocks, is inserted by 



