LEUCITE CRYSTALS FROM VESUVIUS. 31 
The author, in conclusion, affirms that he has never observed 
deposits of peat truly marme. On the shores of the Baltic and the 
Ocean, lagunes are filled with peat, but produced by the same aquatic 
plants as grow on the margin of lakes. He has nowhere met with 
peat-mosses composed of fuci. The marie Zostera, sometimes thrown 
up on the shore in great masses, remains for an indefinite length of 
time exposed to all the changes of the atmosphere without undergoing 
any change in its nature orform. But these are not true formations ; 
and it is impossible to compare such mere accidents to the slow but 
constant operations which nature employs for the production of de- 
posits of peat. 
(J. N.] 
On the Ejection of Leucite Crystals from Vesuvius. By A. Scaccut. 
[From Annali civili, fase. Ixxxvii. L. and B.’s Jahrbuch, 1848, p. 97.] 
In the year 1839 Vesuvius ejected many crystals of pyroxene, which 
fell at a great distance from the crater. On the 22nd of April 1845, 
on the 10th of February and 22nd of June of the last year [1847 ?], 
the last time during the presence of the author, ejections of leucite 
crystals took place. After 1839 only small cones of smoke rose from 
a deep fissure im the crater, but the lava gradually rose up and at 
length, in 1845, flowed over the fissure, and hardening, rose in the 
form of a cone so high that the top could be seen at Naples over the 
edge of the crater. Only occasionally, when the force was most in- 
tense, lava was thrown up into the air, and along with it many leucite 
crystals sometimes quite free from lava. They were as large as peas, 
single, or rarely united in pairs, but according to no regular law, were 
translucent or transparent, striated in certain directions, somewhat 
rounded on the edges, but otherwise very pure forms of crystals. 
On those of the 22nd of June, however, the edges and angles are 
often less acute, and then the form is more spherical, and the whole 
crystal sometimes compressed on the sides which form the trigonal 
angles, these sides also bemmg more extended. On the 22nd of April 
1845 the guide conducted the author to the place where the leucite 
crystals had been thrown out in February ; and he succeeded in 
reaching on a hard bed of lava, which had flowed out on the day 
mentioned, the summit of the burning cone, which was frequently 
ejecting red-hot stones and lapilli. He then saw that the slagey 
lapilli were mixed with small groups of minute leucite crystals more 
or less free from the substance of the lava. These crystals were 
translucent, 0°5—2 millimeters large, whilst the groups had a dia- 
meter of 5—13 millimeters. 
If we now consider that the ejected lapilli and lava fragments were 
so soft when they fell that an impression could be made on the latter 
with a stick; further, that the leucite is more fusible than the mass 
of the lava itself, that the angles and edges of the ejected leucite 
crystals were rounded, and that the lava sometimes formed a varnish- 
like coating over them—it is evident that the power which projected 
