In the province of the Rhine there is a range of mountains, including
several extinct volcanoes, which offer grand and beautiful scenery and
every opportunity for geological study, leading the mind back to the
early ages of the earth.
Let us take an imaginary trip through this region, starting on our
wanderings from the Rhine, where it breaks through the vine-clad slate
mountains of the Westerwald and the Eifel. A short distance above the
mouth of the Ahr we leave its banks, turning to the west, and entering
the mountains at the village of Nieder Breisig. A pretty valley leads
us up through orchards and meadows. The lower hills are covered with
vineyards and the mountains with a dense growth of bushes, so that we
do not obtain an extended view until we reach an elevated ridge.
[Illustration: DISTANT VIEW OF THE VOLCANIC PORTION OF THE EIFEL,
TAKEN FROM THE HEIGHTS OF THE SCHNEIFEL.]
The valley of the Rhine lies far below us, but the glittering surface
of the river, with the little towns, the castles and villas and the
gardens and vineyards on its banks are still visible, while in the
background the mountains of the Westerwald have risen above the hills
on the river. This range stretches out into a long wooded ridge
crowned by cone-shaped peaks of basalt. To the northwest of this lies
Siebengebirge, with its numerous domes and pinnacles, making a grand
picture veiled in the blue mist of distance. On the opposite side we
have a very different view of curious dome and cone shaped summits
surrounded by undulating plateaus or descending into deep ravines and
gorges. It is the western part of the volcanic region of Rhineland
which lies before us, and in the center of which is the Laachersee or
lake of Laach. The origin of these volcanoes is not as remote as many
suppose, but their activity must have continued for a comparatively
long period, judging from the extent of their lava beds.
[Illustration: THE SHORES OF LAACHERSEE.]
There was a time when the sea covered the lowlands of North Germany,
and the waves of a deep bay washed the slopes of the Siebengebirge.
Then the bed of the Rhine lay in the highlands, which it gradually
washed away until the surface of the river was far, far below the
level of its old bed; and then the volcanoes poured forth their
streams of lava over the surrounding plains.
In the course of time the surface of the country has changed so that
these lava beds now lie on the mountain sides overhanging the valleys
of to-day. Some of the volcanoes sent forth melted stones and ashes
from their summits, and streams of lava from their sides, while the
craters of others cracked and then sank in, throwing their debris over
the neighboring country. In the Eifel there are many such funnels
which now contain water forming beautiful lakes (Maaren), which add
much to the scenery of the Eifel. The Laachersee is the largest of
these lakes. In the mean time the channel of the Rhine had been worn
away almost to its present level, but the mountains still sent forth
their streams of lava, which stopped brooks and filled the ravines,
and even the Rhine itself was dammed up by the great stream from
Fornicherkopf forming what was formerly the Neuwied. The old lava
stream which obstructed the river is still to be seen in a towering
wall of rock, extending close beside the road and track that follow
the shore.
[Illustration: CRATER AND LAKE ON TOP OF THE MOSENBERGE.]
After having made these observations, we descend from the height which
afforded us the view of the Vinrt Valley. A clear brook flows through
green meadows and variegated fields stretch along the mountain sides,
while modest little villages are scattered among the fruit trees. On
the other side of the valley rises the Herchenberg, an extinct
volcano. As we climb its sides we see traces of the former
devastation. Loose ashes cover the ground, bits of mica glittering in
the sun, and on the summit we find enormous masses of stone which were
melted and then baked together. In the center lies the old crater, a
quiet, barren place bearing very little vegetation, but from its wall
an excellent view of the surrounding country can be obtained. Not far
from this mountain lies the mighty Bausenberg, with its immense, well
preserved crater, only one side of which has been broken away, and
which is covered with a thick growth of bushes. The ledges of this
mountain are full of interest for the mineralogist. Nearer to Lake
Laach are the Wahnenkopfe, the proud Veitskopf, and other cone-shaped
peaks. To these we direct our steps, and after a long tramp over the
rolling, cultivated plateau, we climb the wood-covered sides of the
great basin in whose depths the Laachersee lies. From the shore of
this lake rise the high volcanic peaks which tower above all the other
mountains.
[Illustration: LAKE GEMUNDEN.]
Tired from our climb through the ashes, which are heated by the sun,
we rest in the shade of a beech-wood, looking through the leaves into
the valley below us, with the old cloisters and the high Roman church
which the monks once built on the banks of the lake.
[Illustration: THE CRATER OF THE HERCHENBERGES.]
To the south of the lake rise other volcanoes, lying on the border of
the fertile Maifeld, which gradually descends to the valley of
Neuwied. Here, at the southern declivity of the group of volcanoes
which surrounds the Laachersee, remarkably large streams of lava were
ejected, covering the surface of the plateau with a thick layer. The
largest of these streams is that from the Niedermendig, which consists
of porous masses of nepheline lava. In the time of the Romans
millstones were made from this mass of rock, and the industry is
carried on now on a larger scale. It is a strange sight which meets
one's eyes when, after descending through narrow passages, he finds
himself in large, dark halls, from which the stone has been cut away,
and in which there are well-like shafts. The stones are raised through
these shafts by means of gigantic cranes and engines. Because of the
rapid evaporation of the water in the porous stone, these vaults are
always cool, winter and summer, and therefore they are used by several
brewers as storehouses for their beer, which owes its fame to these
underground halls.
[Illustration: THE MILLSTONE GALLERIES IN THE LAVA BEDS OF
NIEDERMENDIG.]
[Illustration: ON THE LAVA BEDS OF NIEDERMENDIG.]
Although the traces of former volcanic action are evident to the
student of nature, the Rhine with its mild climate and luxuriant
vegetation has covered many marks of the former chaotic state of the
land. Very little of this beauty is seen on the higher and,
therefore, more severe and barren mountains of the Western Eifel,
through which a volcanic fissure runs from the foot of the high
unhospitable Schneifel to Bertrich Baths, near the Moselle. From the
ridge of the Schneifel the traveler from the north has his first
glimpse of the still distant system of volcanoes. The most beautiful
part of this portion of the Eifel is in the neighborhood of Dann and
Manderscheid. Near the former rises a barren mountain with a long
ridge, on each side of which is a deep basin. These are sunken
craters, which now contain lakes, and near these two there is a third,
larger lake, the Maar von Schalkemehren, on the cultivated banks of
which we find a little village. The middle one, the Weinfelder Maar,
is the most interesting for geologists, for there seems to have been
scarcely any change here since the time of the eruption. On the other
side of the mountain lies the Gremundener Maar, the shores of which
are not barren and waste land, like those of the middle lake, but it
is surrounded by a dark wreath of woods whose tops are mirrored in the
crystal water. Farther to the south, near the villages of Gillenfeld
and Meerfeld, there are more lakes.
[Illustration: THE WEINFELDER LAKE ON THE MAUSEBERGE.]
[Illustration: EASTERN DECLIVITY OF MOSENBERGE NEAR MANDERSCHEID.]
The grandest picture of these ancient events is offered by the
Mosenberg, near Manderscheid, a mighty volcano which commands an
extensive view of the country. Two old craters lie on its double top,
one of which has fallen in, forming a short rocky valley, but the
other retains its original regular shape. In the circular funnel,
whose walls consist of masses of lava stone, rests a quiet, black
lake, that looks very mysterious to the wanderer. Only low juniper
bushes grow near the crater, bearing witness to the barrenness of the
land. From the foot of this mountain an immense stream of lava, as
wide and deep as a glacier, broke forth and flowed into the valley,
where the end of the stream is still to be seen in a high, steep wall
of rock.
[Illustration: THE "CHEESE GROTTO" AT BERTRICH BATHS.]
Similar sights are met all through this western volcanic region, and
we can consider the mineral and acid springs, which are very numerous,
as the last traces of the former disturbances, the products of the
decomposition of the volcanic stones buried in the earth. At Bertrich
Baths there are hot springs which were known to the Romans, for
numerous antiquities dating from their time have been excavated here.
Near these springs, at Bertrich, there is a "Cheese Grotto," which is
a break through the foot of a stream of lava, the stones of which have
not assumed the usual form of solidified columns, but have taken flat,
round shapes which resemble the forms of cheeses.
Now we have completed our wanderings, which required only a few days,
although they extended over this whole volcanic region, and which end
here on the Moselle.--_Ueber Land und Meer; Allgemeine Illustrirte
Zeitung._
* * * * *
[NATURE.]
THE "METEOROLOGISKE INSTITUT" AT UPSALA, AND CLOUD
MEASUREMENTS.
The Meteorological Institute at Upsala has gained so much fame by the
investigations on clouds which have been carried on there during the
last few years, that a few notes on a recent visit to that
establishment will interest many readers.
The Institute is not a government establishment; it is entirely
maintained by the University of Upsala. The _personnel_ consists of
Prof. Hildebrandsson, as director; M. Ekholm and one other male
assistant, besides a lady who does the telegraphic and some of the
computing work.
The main building contains a commodious office, with a small library
and living apartments for the assistant. The principal instrument room
is a separate pavilion in the garden. Here is located Thiorell's
meteograph, which records automatically every quarter of an hour on a
slip of paper the height of the barometer, and the readings of the wet
and dry thermometers. Another instrument records the direction and
velocity of the wind.
This meteograph of Thiorell's is a very remarkable instrument. Every
fifteen minutes an apparatus is let loose which causes three wires to
descend from rest till they are stopped by reaching the level of the
mercury in the different tubes. When contact is made with the surface
of the mercuries, an electric current passes and stops the descent of
each wire at the proper time. The downward motion of the three wires
has actuated three wheels, each of which carries a series of types on
its edge, to denote successive readings of its own instrument. For
instance, the barometer-wheel carries successive numbers for every
five-hundredth of a millimeter--760.00, 760.05, 760.1, etc.; so that
when the motion is stopped the uppermost type gives in figures the
actual reading of the barometer. Then a subsidiary arrangement first
inks the types, then prints them on a slip of paper, and finally winds
the dipping wires up to zero again.
An ingenious apparatus prevents the electricity from sparking when
contact is made, so that there is no oxidation of the mercury. The
mechanism is singularly beautiful, and it is quite fascinating to
watch the self acting starting, stopping, inking, and printing
arrangements.
We could not but admire the exquisite order in which the whole
apparatus was maintained. The sides of the various glass tubes were as
clean as when they were new, and the surfaces of the mercuries were as
bright as looking glasses.
The university may well be proud that the instruments were entirely
constructed in Stockholm by the skillful mechanic Sorrenson, though
the cost is necessarily high. The meteograph, with the anemograph,
cost £600, but the great advantage is that no assistant is required to
sit up at night, and that all the figures wanted for climatic
constants are ready tabulated without any further labor.
But the Institute is most justly celebrated for the researches on the
motion and heights of clouds that have been carried on of late years
under the guidance of Prof. Hildebrandsson, with the assistance of
Messrs. Ekholm and Hagström.
The first studies were on the motion of clouds round cyclones and
anticyclones; but the results are now so well known that we need not
do more than mention them here.
Latterly the far more difficult subjects of cloud heights and cloud
velocities have been taken up, and as the methods employed and the
results that have been obtained are both novel and important, we will
describe what we saw there.
We should remark, in the first instance, that the motion of the higher
atmosphere is far better studied by clouds than by observations on
mountain tops, for on the latter the results are always more or less
influenced by the local effect of the mountain in deflecting the wind
and forcing it upward.
The instrument which they employ to measure the angles from which to
deduce the height of the clouds is a peculiar form of altazimuth that
was originally designed by Prof. Mohn, of Christiania, for measuring
the parallax of the aurora borealis. It resembles an astronomical
altazimuth, but instead of a telescope it carries an open tube without
any lenses. The portion corresponding to the object glass is formed by
thin cross wires: and that corresponding to the eye piece by a plate
of brass, pierced in the center by a small circular hole an eighth of
an inch in diameter. The tube of the telescope is replaced by a
lattice of brass work, so as to diminish, as far as possible, the
resistance of the wind. The vertical and horizontal circles are
divided decimally, and this much facilitates the reduction of the
readings.
The general appearance of the instrument is well shown in the figure,
which is engraved from a photograph I took of Mr. Ekholm while
actually engaged in talking through a telephone to M. Hagström as to
what portion of a cloud should be observed. The latticework tube, the
cross wires in place of an object glass, and the vertical circle are
very obvious, while the horizontal circle is so much end on that it
can scarcely be recognized except by the tangent screw which is seen
near the lower telephone.
Two such instruments are placed at the opposite extremities of a
suitable base. The new base at Upsala has a length of 4,272 feet; the
old one was about half the length. The result of the change has been
that the mean error of a single determination of the highest clouds
has been reduced from 9 to a little more than 3 per cent. of the
actual height. At the same time the difficulty of identifying a
particular spot on a low cloud is considerably increased. A wire is
laid between the two ends of the base, and each observer is provided
with two telephones--one for speaking, the other for listening. When
an observation is to be taken, the conversation goes on somewhat as
follows: First observer, who takes the lead--"Do you see a patch of
cloud away down west?" "Yes." "Can you make out a well-marked point on
the leading edge?" "Yes." "Well, then; now." At this signal both
observers put down their telephones, which have hitherto engaged both
their hands, begin to count fifteen seconds, and adjust their
instruments to the point of cloud agreed on. At the fifteenth second
they stop, read the various arcs, and the operation is complete.
But when the angles have been measured the height has to be
calculated, and also the horizontal and vertical velocities of the
cloud by combining the position and height at two successive
measurements at a short interval. There are already well-known
trigonometrical formulæ for calculating all these elements, if all the
observations are good; but at Upsala they do far more. Not only are
the observations first controlled by forming an equation to express
the condition that the two lines of sight from either end of the base
should meet in a point, if the angles have been correctly measured and
all bad sets rejected; but the mean errors of the rectangular
co-ordinates are calculated by the method of least squares.
[Illustration: N. EKHOLM MEASURING CLOUDS.
This figure shows the peculiar ocular part of the altazimuth,
with the vertical and horizontal circles. It also shows the
telephonic arrangement.]
The whole of the calculations are combined into a series of formulæ
which are necessarily complicated, and even by using logarithms of
addition and subtraction and one or two subsidiary tables--such as for
log. sin²([theta]/2) specially constructed for this work--the
computation of each set of observations takes about twenty minutes.
Before we describe the principal results that have been attained, it
may be well to compare this with the other methods which have been
used to determine the height of clouds. A great deal of time and skill
and money have been spent at Kew in trying to perfect the photographic
method of measuring the height of clouds. Very elaborate cloud
cameras, or photo-nephoscopes, have been constructed, by means of
which photographs of a cloud were taken simultaneously from both ends
of a suitable base. The altitude and azimuth of the center of the
plate were read off by the graduated circles which were attached to
the cameras; and the angular measurements of any point of cloud on the
picture were calculated by proper measurements from the known center
of the photographic plate. When all this is done, the result ought to
be the same as if the altitude and azimuth of the point of the cloud
had been taken directly by an ordinary angle measuring instrument.
It might have been thought that there would be less chance of
mistaking the point of the cloud to be measured, if you had the
pictures from the two ends of the base to look at leisurely than if
you could only converse through a telephone with the observer at the
other end of the base. But in practice it is not so. No one who has
not seen such cloud photographs can realize the difficulty of
identifying any point of a low cloud when seen from two stations half
a mile or a whole mile apart, and for other reasons, which we will
give presently, the form of a cloud is not so well defined in a
photograph as it is to the naked eye.
At Kew an extremely ingenious sort of projector has been devised,
which gives graphically the required height of a cloud from two
simultaneous photographs at opposite ends of the same base, but it is
evident that this method is capable of none of the refinements which
have been applied to the Upsala measures, and that the rate of
vertical ascent or descent of a cloud could hardly be determined by
this method. But there is a far greater defect in the photographic
method, which at present no skill can surmount.
We saw that the altazimuth employed at Upsala had no lenses. The
meaning of this will be obvious to anyone who looks through an opera
glass at a faint cloud. He will probably see nothing for want of
contrast, and if anything of the nature of a telescope is employed,
only well-defined cloud outlines can be seen at all. The same loss of
light and contrast occurs with a photographic lens, and many clouds
that can be seen in the sky are invisible on the ground glass of the
camera. Cirrus and cirro-stratus--the very clouds we want most to
observe--are always thin and indefined as regards their form and
contrast against the rest of the sky, so that this defect of the
method is the more unfortunate.
But even when the image of a cloud is visible on the focusing glass,
it does not follow that any image will be seen in the picture. In
practice, thin, high white clouds against a blue sky can rarely be
taken at all, or only under exceptional circumstances of illumination.
The reason seems to be that there is very little light reflected at
all from a thin wisp of cirrus, and what there is must pass through an
atmosphere always more or less charged with floating particles of ice
or water, besides earthy dust of all kinds. The light which is
scattered and diffused by all these small particles is also
concentrated on the sensitive plate by the lens, and the resulting
negative shows a uniform dark surface for the sky without any trace of
the cloud. What image there might have been is buried in photographic
fog.
In order to compare the two methods of measuring clouds, I went out
one day last December at Upsala with Messrs. Ekholm and Hagström when
they were measuring the height of some clouds. It was a dull
afternoon, a low foggy stratus was driving rapidly across the sky at a
low level, and through the general misty gloom of a northern winter
day we could just make out some striated stripes of strato-cirrus--low
cirro-stratus--between the openings in the lower cloud layer. The
camera and lens that I use habitually for photographing cloud
forms--not their angular height--was planted a few feet from the
altazimuth with which M. Ekholm was observing, and while he was
measuring the necessary angles I took a picture of the clouds. As
might have been expected under the circumstances, the low dark cloud
came out quite well, but there was not the faintest trace of the
strato-cirrus on the negative. MM. Ekholm and Hagström, however,
succeeded in measuring both layers of cloud, and found that the low
stratus was floating at an altitude of about 2,000 feet high, while
the upper strato-cirrus was driving from S. 57° W. at an altitude of
19,653 feet, with a horizontal velocity of 81 and a downward velocity
of 7.2 feet per second. This is a remarkable result, and shows
conclusively the superiority of the altazimuth to the photographic
method of measuring the heights of clouds.
Whenever opportunity occurs, measures of clouds are taken three times
a day at Upsala, and it may be well to glance at the principal results
that have been obtained.
The greatest height of any cloud which has yet been satisfactorily
measured is only 43,800 feet, which is rather less than has usually
been supposed; but the highest velocity, 112 miles an hour with a
cloud at 28,000 feet, is greater than would have been expected. It may
be interesting to note that the isobars when this high velocity was
reported were nearly straight, and sloping toward the northwest.
The most important result which has been obtained from all the
numerous measures that have been made is the fact clouds are not
distributed promiscuously at all heights in the air, but that they
have, on the contrary, a most decided tendency to form at three
definite levels. The mean summer level of these three stories of
clouds at Upsala has been found to be as follows: low clouds--stratus,
cumulus, cumulo-nimbus, 2,000-6,000 feet; middle clouds--strato-cirrus
and cumulo-cirrus, 12,900-15,000 feet; high clouds--cirrus,
cirro-stratus, cirro-cumulus, 20,000-27,000 feet.
It would be premature at present to speculate on the physical
significance of this fact, but we find the same definite layers of
clouds in the tropics as in these high latitudes, and no future cloud
nomenclature or cloud observations will be satisfactory which do not
take the idea of these levels into account.
But the refinements of the methods employed allow the diurnal
variations both of velocity and altitude to be successfully measured.
The velocity observations confirm the results that have been obtained
from mountain stations--that, though the general travel of the middle
and higher clouds is much greater than that of the surface winds, the
diurnal variation of speed at those levels is the reverse of what
occurs near the ground. The greatest velocity on the earth's surface
is usually about 2 p.m.; whereas the lowest rate of the upper currents
is about midday.
The diurnal variation of height is remarkable, for they find at Upsala
that the mean height of all varieties of clouds rises in the course of
the day, and is higher between 6 and 8 in the evening than either in
the early morning or at midday.
Such are the principal results that have been obtained at Upsala, and
no doubt they surpass any previous work that has been done on the
subject. But whenever we see good results it is worth while to pause a
moment to consider the conditions under which the work has been
developed, and the nature and nurture of the men by whom the research
has been conducted. Scientific research is a delicate plant, that is
easily nipped in the bud, but which, under certain surroundings and in
a suitable moral atmosphere, develops a vigorous growth.
The Meteorological Institute of Upsala is an offshoot of the
Astronomical Observatory of the university; and a university, if
properly directed, can develop research which promises no immediate
reward in a manner that no other body can approach.
If you want any quantity of a particular kind of calculation, or to
carry on the routine of any existing work in an observatory, it is
easy to go into the labor market and engage a sufficient number of
accurate computers, either by time or piece work, or to find an
assistant who will make observations with the regularity of clockwork.
But original research requires not only special natural aptitudes and
enthusiasm to begin with, but even then will not flourish unless
developed by encouragement and the identification of the worker with
his work. It is rarely, except in universities, that men can be found
for the highest original research. For there only are young students
encouraged to come forward and interest themselves in any work for
which they seem to have special aptitude.
Now, this is the history of the Upsala work. Prof. Hildebrandsson was
attached as a young man to the meteorological department of the
astronomical observatory, and when the study of stars and weather were
separated, he obtained the second post in the new Meteorological
Institute. From this his great abilities soon raised him to the
directorship, which he now holds with so much credit to the
university. M. Ekholm, a much younger man, has been brought up in the
same manner. First as a student he showed such aptitude for the work
as to be engaged as assistant; and now, as the actual observation and
reduction of the cloud work is done by him and M. Hagström, the
results are published under their names, so that they are thoroughly
identified with the work.
Upsala is the center of the intellectual life of Sweden, and there,
rather than at Stockholm, could men be found to carry out original
research. It redounds to the credit of the university that it has so
steadily supported Prof. Hildebrandsson, and that he in his turn has
utilized the social and educational system by which he is surrounded
to bring up assistants who can co-operate with him in a great work
that brings credit both to himself, to themselves, and to the
institute which they all represent.