F. S. Bendant on the Calcareous Tiifas of Hungary. 31 
escarpes & pic to a moderate height, at the edge of the little 
plain of Old Buda. The lower part is a coarse tufa, of a yel- 
lowish-white colour, full of infiltrations of calcareous spar 
which here and there forms brilliant veins in the midst of 
the rock, or even stalactites in the cavities which abound in 
its substance. In proportion as we proceed upwards, the tu- 
fa becomes more compact; and in the upper parts, it pre- 
sents an extremely solid, and very hard rock, with a splin- 
tery fracture, perforated with irregularly tubular holes, some- 
times empty, sometimes crusted, or even filled with white trans- 
parent calcareous spar. I have distinguished, in some parts, 
vegetable impressions, helices, and other shells which appear to 
belong to the genus paludina, and to the species designated by 
the name of paludina impura. These deposits of calcareous tu- 
fa have been wrought in many points as a building stone, espe- 
cially in the more solid parts. The works have been carried 
on, as it would seem, for many ages ; for these stones have been 
used in some parts of the fortress of Vissegrad, which shows, 
that, at the period when that fortress was built, the tufas in ques- 
tion were nearly such as we see them at the present day. I have 
discovered no trace of the springs from which they have derived 
their origin; and nowhere have I observed modern augmenta- 
tions made to the mass. 
It was without doubt, also, at a very remote epoch, that the 
calcareous tufas were formed, which we see on the western side 
of Bloksberg, and which are particularly remarkable on account 
of the planorbes which they contain in certain points. These 
tufas are very solid, of a whitish or yellowish colour, and have, 
in some parts, a great analogy with the Travertino of the neigh- 
bourhood of Rome, which is also an ancient tufa. No traces of 
the waters from which these masses have been deposited, are to 
be seen now at Bloksberg : it is probable that they were formed 
at a time when that mountain was altogether different from 
what it is at the present day. The presence of planorbes indi- 
cates, that there were other waters than those of an incrusting 
spring, which might be imagined upon the sides of the moun- 
tain ; there must have been a stream or body of fresh water of 
some kind, where the planorbes could have lived ; and at the 
