Bol 
H. J. Joanston-Lavis, who very emphatically contended for the tufa- 
character of the piperno, and who attempted to give a peculiar 
strength to his argument by writing: 
“All geologists who have attempted to explain these principal 
“peculiar characters, have utterly failed to do so, and had I space 
“to enumerate many minor ones, the difficulty would be still greater. 
“Unfortunately, most of these inclusions have been jumped at, as 
“the result of that useful instrument though unfortunate misleader 
“of geology, the microscope, which has caused investigators to forget 
“that it is only one means to an end, and that field investigation is 
“of far greater importance.” *) 
On account of the aversion which Jounston-Lavis has to the 
microscope it will be impossible to convince him of the difference 
between a piperno and a pipernoid tufa. But we point out the fact, 
that it was exactly the “field-geologists” who, as yet, not knowing 
anything of the application of “that useful instrument” to the domain 
of petrography, have ascertained that piperno was an eruptive rock. 
Besides Lrop. von buch we need only mention Scipio BREISLAK *), 
H. Apicn ®), J. Rora, G. Gouiscarpi*). It is likewise a fact known 
long since that a tufa may obtain a pipernoid structure in the way 
surmised by Jounston-Lavis, but the investigators knew, also without 
the help of the microscope, how to distinguish such like rocks from 
real piperno. °) 
The rhyolite of the Pelapis Islands is a stronger evidence of the 
fact that the piperno-structure is not connected with a tufa-formation 
as the porosity of the main mass of the rock is as insignificant as 
that of the “Schlieren” whose form has as little resemblance to that 
of volcanic ejections. 
1) Notes on the Pipernoid Structure of Igneous Rocks: Natural Science II]. London- 
New-York 1893, p. 219. 
*) Voyages physiques et lythologiques dans la Campanie. II. Paris An. IX (1801) 
p. 42—47.— Institutions géologiques. III. Milan 1818, pp. 154—156. 
35) Ueber die Natur und den Zusammenhang der vulkanischen Bildungen. Braunschw. 
1841, p. 39. 
4) Il piperno. Rendic. Accad. Sc. fis. e Mat. VI. Napoli 1867, p. 221—226. 
5) J. Rorr, Der Vesuv und die Umgebung von. Nerpel. Berlin 1857, p. 512. — 
G. vom Ratu. Mineralogisch-geognostische Fragmente aus Italien. Zeitschr. d, 
Deutschen geolog. Gesellsch. XVIII, 1866, p. 633—634, 
