304 Revieio cf Recent Geological Literature 
petrographic forms of Vogelsang, and thus displacing Levy's micropeg- 
matite, which has preciiely the same meaning. Again, professor Ros- 
enbusch recapitulates the structures of paleeovolcanic rocks a.a a, felsite 
habit, a porphyritic habit, and a doleritic habit; these are precisely the 
characters expressed by M. L^vy in the phrases structures of acid rocks, 
structures microUtic, and structures ophitic. 
Such is the nature of M. Levy's indictment for changes of nomen- 
clature. In our judgment, very many of Rosenbusch's terms are hap- 
pily chosen and expressive. Next in honor to him who gives exist- 
ence to a new conception is he who gives it to the world in fit phrase. 
M. Levy would undoubtedly recognize the superior fitness of many of 
Rosenbusch's terms ; but there is ground for complaint when a change 
of terms brings no gain in brevity or elegance, or truthfulness, but 
simply bequeathes synonymy and perplexity to hinder the progress 
of the learner. 
More important are M.Levy's criticisms of the subject matter of profes- 
sor Rosenbusch's work. In reference to the doctrine thatthe holocrys- 
talline rocks have but one period of consolidation, he says : "We know 
of but a single series where the two periods do not exist ; that is the 
saccharoidal granulites (structure microUtic of M. Rosenbusch, in 
which all the elements have proper crystalline forms (idiomorph, pan- 
idiomorph) and date from the second period, the first making almost 
complete default." He shows, also, that most of the idiomorphic 
rocks are not strictly as described. Depth is only one of the factors 
determining the crystalline state of a rock. "Mineralizers" often 
play a preponderating role in the structures of acid rocks. Rocks of 
deep origin may present a porphyroid structure in certain special cir- 
cumstances where the factors of crystallinity abruptly diminish. Even 
granitoid rocks may have had two periods of crystallization, though 
the products differ little in crystalline dimensions. In the view of M. 
Rosenbusch, there exist a great number of gabbros and diabases in 
the effusive or bedded condition. But in one part of his work he 
makes the statement that the gabbros with granular structure are the 
intratelluric form, the diabases with ophitic structure, the intrusive 
form ; the augite-porphyrites and the melaphyrs or basalts, with mi- 
croUtic structure are the bedded and veined forms of one and the same 
magma; while, by reading attentively almost any of his chapters, we 
meet with all these structures and all these passages in terranes the 
most diverse. The explanation of this state of things is afi'orded by 
the experiments of MM. Fouque and L^vy, who have reproduced all 
these structures by artificial fusion, and by baking more or less pro- 
longed in one or two periods. With these and other considerations, 
it is argued that the division of "rocks of deep origin" is artificial. 
More artificial is the division of intrusive rocks. Take the family of 
lamprophyres. Petrographically, they distribute themselves over 
the entire series, from microgranulites slightly basic, to and 
including melaphyrs, embracing micaceous, amphibolic and pyr- 
