the Mediterranean naturalist 
returns, plant life disappears, and once again the 
island dons that sterile, desolate garb which has 
earned for her such an unen viable reputation. But 
these periodical alternations have not been effected 
without leaving behind them some traces of their 
existence. This annual decay must be, and is fol- 
lowed by its usual physical accompaniments, na- 
mely, the disintegration of the surface upon which 
the plants have rested, and thus new surface in- 
dentations are formed and old ones are, by the 
latest opera ion, still further enlarged, 
1 do not say that this is the only cause to which 
these surface excavations are due, but it, at least 
seems to me to be the principal one. 
From the preceding observations it will be seen 
that I have considered the effects wrought by one 
only of the numerous class of agents that are con- 
stantly engaged in wearing down the surfaces' of 
the islands strata. 
It is, however, one the importance of which is 
not always so fully appreciated as it should be, for 
though it works as effectively as the others, yet by 
reason of its subtle methods, and the fact, that 
under certain conditions it exerts directly opposite 
effects, it does not always get the full credit for 
the work that it is actually responsible for. 
J. H. C. 
The Flora of Northern Germany during 1 
the Middle Ages. 
We extract the following notes from an interes- 
ting paper by Dr. E.H.L. Krause on the Flora of 
Northern Germany in the Middle Ages, which ap- 
pears, with a map, in the current number of ‘Pet- 
erman n’s Mitteilungen.’ The author deals mainly 
with the period from the twelfth to the beginning 
of the sixteenth century — the materials relating to 
eailier periods being very scanty — and concerns 
himself only with the vegetation of uncultivated 
lands. North-west Germany was in the Middle 
Ages rich in forests. In Saxony there was less 
forest in the sixteenth century than the twelfth to 
the fifteenth centuries. In Oldenburg to-day 
there are Oaks and beeches estimated to lie over 
500 years old, notably in the so-called virgin forest ! 
305 
of the Varel district. The general character of the 
forests of Schleswig-Holstein in the Middle Ages 
was deciduous, with a predominance of oaks and 
beeches, pines being absent. The West Bailie 
coast was from the eighth till the twelfth century 
little inhabited, and remained thickly wooded, the 
forests being much less broken up by heaths and 
moors than those of North-west Germany. The 
central mountains of Western Germany were also 
well covered with forests. The heights in the 
basin of the Moselle, which had been cleaved of 
trees bv the Romans, were, shortly after the occu- 
pation of the country by the Franks, again clothed 
with forests. Turning to the three central provin- 
ces of Thuringia, we find that the heights to the 
north and south of the Harz Mountains were wood- 
ed, and besides oaks and beeches, aspens and 
birches were very common. The flora of the 
Sarmatian lowlands stood in striking contrast to 
that of the western provinces. In the former, 
pinewoods were everywhere abundant, the Scotch 
pine being in many places the most common tree. 
In this region the western limit of the pine forests 
appears to have been in some measure coincident 
with the boundary between the Slav and Low 
German populations.' On the East Baltic coasts 
the red pine was more common, and beech almost 
entirely disappeared. The higher mountain ranges 
were characterised by the presence on their lower- 
slopes of the silver-leaved fir. This tree lias com- 
pletely disappeared in the Harz Mountains. It is 
doubtful whether this species of fir flourished in 
the highlands of Roland in the Middle Ages. Dr. 
Krause’s paper forms a valuable contribution to 
the historical study of the geographical distribution 
o 1 plants, and his map is carefully worked out. 
Journ R. G. S. 
SCIENCE ECHOES. 
Phenomena of a British Coal Mine. — A newly 
opened coal-mine near Manchester, Eng., lies at 
the great depth of about 1000 yards, and the bor- 
ing presents the curious phenomenon of passing 
down, from one seam of coal to another one 400 
1 yards geologically higher. This is due to a rove;- 
