168 On the Porosity of Agates, Calcedonies, Sc. 
Weisselberg, near Oberkirchen, in the district of Wendel, 
produces fine specimens, but in small quantity. Bamstedt 
relates that one was found in the year 1844, and weighed 
100 1b. It was sold in its crude state for 700 Rh. guilders. 
The purchases between the diggers and dealers are made 
by mutual understanding, and generally without any pre- 
vious trials being made or desired, the price being agreed on 
by the weight. 
That the different varieties of quartz which form agate 
balls and amygdaloidal-shaped pieces, vary in their porosity 
has been proved by an interesting experiment of Von Kobell, 
who applied fluoric acid to polished agate where the different 
streaks were not regularly developed and only slightly 
visible. 
Still more direct proof of the porosity of calcedony has 
been brought forward by Gautieri.* Near Vincenza there 
occur balls of caleedony, which contain, in their interior, wa- 
ter or air, and sometimes both, so that, through the trans- 
lucent balls, we can always observe the upper part of the 
contained bubble by giving them a slight motion. These 
stones are called Enhydri. Gautieri placed one of these cal- 
cedonies, which contained no water, but only air, for some 
weeks in water, and observed the result. Some had, and 
some had not, absorbed or taken in the water into their hol- 
low cavities ; those which had not had turned clearer and 
harder. Such masses, when kept in a dry place, lose their con- 
tained water, and yet no opening or fissure can be observed. 
This proof of their porosity was thus shewn by Gautieri. 
Fuchs lately repeated these experiments with similar masses 
of calcedony from Schio, obtained from the Zuggiano and 
Lago Mountains ; he did not succeed so well as Gautieri, but 
yet his experiments are convincing of the fact in question. 
A longer immersion in water, accompanied by strong pres- 
sure, is not sufficient to bring the water back into the empty 
cavities. It may, however, be done by gradually heating the 
* Untersuchung iiber die Entstehung, Bildung und den Ban des Chalcedons. 
Jena, 1800, 8S. 157. 
t Beitrag zur lehre von den Erzlagerstatten. Wien, 1846, 8. 41. 
