the government with a balloon for signalling purposes, which he has
invented, is about to exhibit a balloon of the same kind at the Crystal
Palace, Sydenham. This aërostat will have a capacity of eighty thousand
cubic feet, sufficient to give it the necessary lifting power to carry
up several passengers. The balloon will be a captive one, like that
exhibited at Paris in 1878, and will, like its huge forerunner, be
hauled down to the earth after each ascent, by steam-power. It will
ascend for the amusement of visitors during the daytime, telephonic
communication being maintained between the car and the earth; while at
night it will be illuminated by the electric light, so that Mr Bruce’s
method of signalling may be fully demonstrated.
The number of deep wells sunk in London and its neighbourhood during
the past thirty years has had the effect of lowering the general
water level in the chalk to the amount of about twelve inches
annually. But there is still a very large quantity available—so the
experts say—without sinking shafts to extraordinary depths. Much
interest attaches to the subject at the present time on account of
the threatened action of the London corporation to sink wells for
themselves, as the strongest protest they can offer against the high
charges of the Water Company supplying the city.
The title of one of Turner’s best pictures, ‘The _Téméraire_ towed to
her last Moorings,’ comes to the mind as one hears that the _Great
Eastern_, the largest steamship ever built, too large, indeed, to
be profitably worked, has steamed round to Liverpool to serve as a
show-place during the Maritime Exhibition there. After this last duty
is done, this monument of Brunel’s wonderful skill will take up her
position as a coal-hulk.
People who rejoice in the possession of wealth and who have plenty
of time on their hands, generally develop into ‘collectors.’ Coins,
pictures, books, china, orchids, postage-stamps, &c., have their
periods as the fashionable things to gather together. The last craze of
this kind is devoted to engraved plates. Old copper plates are perhaps
the best; and the way to preserve and exhibit them is as follows:
the plate is rolled with ink and polished, just as if an impression
were required of it. It is then set aside for the ink to dry, when it
receives a coating of clear varnish, to protect it from the oxidising
action of the air. It is now framed and hung up like an ordinary
picture.
The Kyrle Societies have seldom reason to congratulate iron
manufacturers on the progress of their art; but it seems as if they
might heartily rejoice in a Report recently made at the instance of
the North-eastern Steel Company as to the utilisation of an important
by-product of the steel manufacture. The Report is on the results of
experiments made to test the value of basic cinder as a manure, and
is the joint work of Professor Wrightson and Dr Munro, of the College
of Agriculture, Downton, Salisbury. Basic cinder, or basic steel
slag, is the broken-up and useless lining of the converters used in
the Thomas-Gilchrist process for dephosphorising iron, and is a bulky
by-product of the manufacture. It contains from sixteen to nineteen
per cent. of phosphoric acid combined with lime and other bases; and
the Report in question puts it beyond a doubt that the undissolved
phosphates of the cinder have an available and remarkable value for
manurial purposes. Extensive and elaborate experiments conducted
at Downton and elsewhere showed decisively that this heretofore
inconvenient substance is an excellent fertiliser for swedes and other
turnips, as well as for grass. It seems to be positively better for
this purpose than ground coprolites, and only a little less effective
than superphosphate. This interesting Report is published at the _Daily
Exchange_ Offices, Middlesborough. Similar experiments have been
attended with like success in Germany; and from _Le Temps_ it would
appear that enterprising agricultural chemists are already in treaty
with some of the blast-furnaces of Alsace-Lorraine for the purchase of
all the slag produced by them.
The history of the recovery of a portion of the mails from the Cunard
steamer _Oregon_, ought to supply chemists and inventors with a good
deal of food for thought. Before the vessel sank, a portion of the
mail was recovered, but by far the greater portion went down with
her. This was the case with the registered letters, the portion of
the mail containing securities, coupons, &c., to the value of at
least one hundred thousand pounds, besides drafts, letters of credit,
&c., of which the value was unknown. A notice has been issued by the
Liverpool postmaster which tells us that the whole of these registered
letters have been recovered. The letters were thoroughly soaked, but
the post-office authorities dried them as carefully as they could and
sent them on to their destination. All the mail-matter that has been
recovered was badly damaged by wetting, while the bags which were
subjected to long-continued soaking at the bottom of the sea were
very much damaged. In one case, a fifty pound note sent from Frome to
Chicago was delivered only just recognisable, but still sufficient to
insure its being honoured.
These facts have led an American scientific journal to urge the
necessity for waterproof mailbags, waterproof paper, and waterproof
ink. Waterproof mailbags alone will not be sufficient, as, in the
process of handling them or raising them from a sunken vessel, they
are liable to be rendered leaky. Waterproof paper, again, would be of
no service unless it was accompanied by waterproof ink. The mailbags
need only be waterproof in the ordinary acceptation of the term; and if
there could be certainty that they would remain so, nothing more would
be needed to protect documents or anything else placed in them; but as
holes are likely to be worn or torn in them, the only final resource
is the production of paper and ink that will resist the prolonged
action of sea-water. If such a paper and ink can be produced at a
reasonable cost, they would meet with a ready market throughout the
civilised world. But the paper must be lighter, more flexible, and more
opaque than the waterproof parchment paper now obtainable.
The lesson which the loss of the _Oregon_ seems to teach the commercial
world is, that a convenient waterproof paper is required for
transatlantic correspondence. Modern chemistry and mechanical invention
ought to be able to meet this want.
No class of the community has received so much good advice as that to
which the farmer belongs, and it would be a wonder if he did not resent
some of it, and say that it is not good advice that is wanted most, but
good seasons. However, when a practical lesson comes within one’s reach
for the better utilisation of available material, only a foolish person
would neglect to learn it. In the model dairy at the Brighton Show,
last summer, Professor Long gave an explanatory demonstration of the
simple methods of making three kinds of soft cheese, by the employment
of tinned-iron hoops, beech-boards, straw-mats, milk-vessels,
draining-shelves, and a thermometer. In the Journal of the Bath and
West of England Society, he has recently drawn attention to the subject
again, and explains his method whereby the farmer may utilise his
skim-milk by the profitable manufacture of soft cheese. It seems that
anybody can learn the processes; and a few experiments will teach the
practice of ripening the cheeses in an apartment having a regulated
temperature proper for the development of the necessary white mould,
followed by blue mould, producing the most accepted flavour.
From a gallon of ‘whole’ milk, costing sixpence, Professor Long
made Brie cheese—the most famous of French varieties—worth, at ten
days to three months old, from one shilling to one shilling and
sixpence; from half a gallon of milk, half of it skim-milk, valued at
twopence-halfpenny, he made Coulommiers, a round cheese worth at least
eightpence; and from skim-milk only, costing about one penny, he made a
square variety, of his own invention, named Graveley cheese, partaking
of the qualities of the Limburg of Germany and the Livarot of France.
We understand that nearly six millions of the delicious Brie cheeses
are made annually in certain districts of France for the Parisian
market. An important point will be gained, however, in this country,
if some of our farmers begin to convert their skim-milk into a product
which will sell at three or four times the value of the milk.
Honey-wine is said to be excellent; and Dzierzon—one of the most famous
German writers on scientific bee-keeping—tells us that it is often
manufactured by peasants in Eastern Europe. It is made as follows:
Twenty-five pounds of honey are mixed with four and a half gallons of
water in a bright copper boiler, the mixture being gently boiled and
constantly skimmed during half an hour. Three pounds of finely powdered
chalk are then gradually added, under constant stirring. The tough scum
which rises to the surface is skimmed off, and when no more rises,
the liquid is poured into a wooden vessel, where it is allowed to
settle. The liquid is then carefully decanted into the cleaned kettle,
mixed with six pounds of finely powdered and recently burned charcoal,
and raised to boiling. It is now once more poured into the wooden
vessel, allowed to cool, and then filtered through felt or flannel.
It should be stated that the chalk is added to neutralise free acid,
while the charcoal removes the waxy taste. The filtered liquor is then
transferred to the boiler, mixed with the white of twenty-five eggs,
and raised to boiling, when the coagulated albumen will have clarified
the liquid. After having kept the liquid at a gentle boil for one hour
longer, it is allowed to cool, and is then poured into a cask, which
must not be quite full, and the bung-hole covered with a piece of clean
linen. In this condition it is allowed to remain until fermentation
has been completed. When it is perfectly clear, the liquid is drawn
off into bottles. We are told by Dzierzon that this wine, if properly
prepared, resembles the best brands of Madeira, and is a truly royal
beverage. It keeps for any length of time, provided the bottles are
stored in a cool cellar.
A NEW THEORY OF DEW.
The explanation of the formation of dew and hoar-frost which Dr Wells
published about seventy years ago, has been almost universally accepted
as satisfactory ever since. Shortly stated, Dr Wells’ ‘Theory of Dew’
is as follows: Air always contains a certain amount of moisture in the
form of invisible vapour. The hotter the air is, the more vapour will
it contain. Thus, during a warm day, a good deal of moisture passes
into the air; and when the temperature falls in the evening, some of it
is deposited as a fine mist. But even when this mist does not appear,
dew is formed. As soon as the sun is down, especially if it is a clear
evening, the grass, trees, shrubs, and even the soil itself rapidly
get cooled by radiating into space the heat which they contain. These
cooled bodies in turn cool the warm air above them, and this causes it
to deposit more or less of its moisture, which appears either as a film
or in minute drops of dew. The points of the grass, small twigs, and
all other good radiating surfaces are cooled the most; and accordingly
we find the dewdrops most abundant on these bodies; whilst on metal or
hard stone surfaces, which are poor radiators, we seldom or never find
any dew. A clear, cloudless sky, which promotes radiation, is always
favourable to the formation of dew; but on cloudy nights, little is
formed, because the clouds return the heat radiated from the earth.
Hoar-frost is only dew deposited on bodies cooled below the
freezing-point. It is formed in winter when the temperature of the
air during the day is only a little over this point. At night, the
grass and ground are soon cooled below thirty-two degrees Fahrenheit,
and what moisture is deposited appears as minute ice-crystals or
hoar-frost.
Many experiments can be cited which tend to strengthen and confirm
this explanation. Thus, every one is familiar with the fact of glass
bottles, mirrors, &c., being covered with moisture on being brought
into a warm room. The same thing happens with a cold cabbage leaf, or
with a bundle of vegetables or a bunch of flowers. On a cold night,
the windows of a warm room soon get dimmed. Still more striking is a
phenomenon which frequently occurs in countries where the temperature
is much below the freezing-point in winter. The houses are well heated,
and if a number of people are together, as in a ballroom, the air soon
becomes moisture-laden. If the ventilation is not over-good, it may
happen that a door or window will be opened. With the rush of cold air
from without, the merry-makers are often alarmed by being suddenly
covered with hoar-frost, or sometimes even a shower of snow. This does
not come from the outside, as it occurs most readily on cold, clear,
starlit nights. It is the moisture of the air of the room suddenly
cooled below freezing-point that appears as snow or hoar-frost. Many
similar experiments may be noticed, all of which are satisfactorily
accounted for on Dr Wells’ theory.
Yet, within the last few months, Mr Aitken, in a communication to the
Royal Society of Edinburgh, has brought forward many observations, and
the results of numerous experiments, which appear to prove that Dr
Wells’ theory of dew is not, after all, correct.
The essential difference between the old and the new theories is as
to the source of the moisture which forms the dew. Instead of being
condensed from the air above by the cooled vegetation, Mr Aitken
maintains that it comes from the ground. The author of the original
theory admitted that some of the dew might come from below, but
affirmed that it must be an exceedingly small proportion. Mr Aitken’s
experiments, on the contrary, seem to prove that most if not the whole
comes from the ground.
It is quite clear that the grass and soil do get rapidly cooled on
dewy nights; but if they are below the temperature of the air above,
the ground just under the surface is much warmer. Thermometers placed
on the surface of grass were often found ten to eighteen degrees
lower than those placed under the surface among the stems. In such
circumstances, vapour must be rising from the soil, and part of it will
condense on the grass, which has been cooled by radiation. By carefully
weighing small squares of turf cut from a lawn before and after the
appearance of dew on them, it was always found that they _lost_ weight.
If the dew had condensed out of the surrounding air, the turf would
have _gained_ in weight by the amount of dew deposited. It was thus
clear that vapour was rising from the ground, only part of which was
condensed on the grass, the remainder passing into the air.
Another experiment, pointing to the same conclusion, was made by
inverting thin trays over the grass. On dewy nights these trays were
always found wet on the under surface; and the grass below them was
always much wetter than that freely exposed outside. The moisture
rising from the ground was evidently trapped and condensed, instead of
being allowed to pass freely into the atmosphere.
The explanation of the absence of dew on the surface of stones, roads,
and other hard surfaces, on the old theory was, that these, being poor
radiators, did not get much cooled. But closer observation shows that
dew does form on stones and clods and gravel, only it is chiefly on the
under surfaces. Thus, slates laid over both hard and gravelly roads
are always found dripping wet on their under surfaces on dewy nights;
while their upper surfaces and the surrounding roads are dry. During
frost, too, clods and stones on the surface of the soil are almost
always found to be covered with hoar-frost, showing that the moisture
is trapped as it rises from the soil.
But perhaps the most interesting observations and experiments were
those made to determine the origin of the ‘dewdrops’ on grass and
vegetables. In the first place, it is found that these drops do not
appear on all plants. Some are wet, while others growing alongside
are dry, though there could be no great difference in their radiating
power. Then the leaves do not get wet all over, but only at the edges
and on the tips. A closer observation reveals the fact that these
so-called ‘dewdrops’ are formed at the end of the minute veins of
the leaves and grass, and are not now recognised as dew at all, but
moisture exuded from the interior of the plants themselves. Moreover,
these drops always appear before the true dew in the evening, and
very often are seen when no true dew is formed. They even appear when
the vegetables are placed under conditions where condensation of the
surrounding water-vapour is impossible, and must, therefore, be due to
the vital activity of the plants.
Another observation may be mentioned which clearly shows that moisture
rising from below may become condensed on the cooled surfaces of loose
material. If the weather is at all cold, the beard and moustaches get
covered with moisture; and in very cold climates, the eyebrows, hair,
and whiskers get covered with a coating of hoar-frost. The moisture
which forms this certainly comes from the body, which is always at a
much higher temperature than the surrounding air.
All these observations and experiments have led to the conclusion that
moisture is constantly being given off from the earth; and that, except
on the rare occasions when a warm moisture-laden wind blows gently over
a previously cooled surface, it only returns to the surface of the
ground after being condensed into rain, sleet, snow, or hail. Dew is
only a portion of the outward current trapped on the exposed and cooled
surfaces of the grass and other bodies.
COMRIE EARTHQUAKES.
Regarding earth-tremors or earthquakes, which, curiously enough,
seem to be mainly confined in Scotland to Comrie, in Perthshire, a
correspondent writing from Comrie kindly favours us with the following
notes as to the erection which is there devoted to the registering of
earthquakes. Our correspondent says:
I recently visited the building with a view of giving you a few notes
as to its history and construction. I may state that about fourteen
years ago, the British Association applied to Mr Drummond of Drumearn
for leave to erect a house on his property, which he at once granted
free of charge, and assisted to defray the cost of erection.
The reason why the British Association selected a site here and erected
this earthquake-house at Comrie, was on account of the long-continued
periodical shocks that had been felt in Upper Strathearn, particularly
from the year 1780 to 1848. About the former date, they had been rather
severely felt over the whole district, and damage to some extent
done to buildings. On a sheet of water near to Lawers House, the ice
was shattered to pieces. Some of the inhabitants at that time kept a
record of their occurrence; and we believe the late Sir David Dundas,
of Dunira, had a seismometer placed on his estate in Glenlednoch, to
the north of Comrie; but there seems to be no evidence to show that
it had ever indicated any shock. Coming down to the year 1839, the
inhabitants of the village of Comrie were greatly alarmed, about eleven
o’clock on the night of the 23d of October, by one of the most violent
tremors that had been experienced there; and the good people rushed
out of their houses and assembled in the old Secession Church for
prayer, which was conducted by the Rev. R. T. Walker, the minister of
that church. Many others fled to the hills. But no serious damage was
done to property, save some rents in the chimneys. From 1839 to 1847,
tremors continued to be more frequent, causing considerable alarm by
the movements of furniture and crockery.
The work of erecting the building proposed by the British Association
was carried out under the care of the late Dr James Bryce of Glasgow,
who resided here for many seasons, and was well acquainted with the
locality and its geological formation. The site chosen is a rising
ground near Drumearn House, and is built on rock that is supposed to
extend a considerable distance westward. The building is stone, and
slated, and is about seven feet square inside. The floor is laid with
Arbroath pavement, on solid rock, and is overlaid with fine sand, on
which are placed two boards, at right angles to each other. These
boards are six feet long by nine inches broad, and on each are placed,
standing, nine round wooden pins, varying from the fourth of an inch to
an inch and a half in diameter, but all of one height (eight inches).
The building is in excellent condition, and the pins or markers are
in their places, awaiting the action of an earthquake to record the
desired information as to the severity and direction of this now
seemingly extinct agency of force in Upper Strathearn. The size of pin
or cylinder thrown down, and the direction in which it falls, indicate
the strength of shock as well as its direction. Any one who feels
interested and may wish to visit the building will readily get access
by applying to Mr Drummond.
Many theories have been propounded as to the cause of the earthquakes
which have visited this district. The late Mr Patrick M‘Farlane of
Comrie, who took a great interest in them, erected a seismometer in
the steeple of the parish church of Comrie, which was visited by many
of the members of the British Association and others; but so far as
we are aware, it never registered any markings. It was a very simple
apparatus. The pendulum was of considerable length, and all but rested
on a table overlaid with magnesia, which, being light, offered no
resistance to the oscillation of the pendulum. A few slight shocks
occurred between 1847 and 1877, but these attracted little notice.
I may remark that no earthquake had, till recently, been felt here for
some years, consequently, there had been no registering. But on Sunday
morning 18th April last, at one o’clock, and again on Thursday the
22d of the same month, about half-past five A.M., a slight earthquake
occurred. I visited the earthquake-house on both occasions; but there
were no markings, none of the pins having fallen.
WHICH?
If thou art false as thou art fair,
And false the fairest fair may be,
Again the wondrous power to snare,
Again the siren’s self we see.
There’s danger in those dimpling smiles,
It glances from that witching e’e,
And he who would escape thy wiles,
Must quickly from the tempter flee.
For better far, as sages tell,
From fickle fair to bid adieu,
Than fall beneath the magic spell
Of charms the heart may ever rue.
Beware, if false, of beauty bright,
Beware that luring beacon’s ray,
For, oh! the love that trusts its light,
May drift a wreck ere dawn of day.
But if thou’rt true as thou art fair,
Art leal in heart, though seeming gay,
Wouldst ever constant prove, and ne’er
With faithful heart all faithless play,
Then thou’rt a gem worth more than gold,
More precious than the ruby rare,
More to be prized than wealth untold,
True heart enshrined in form so fair.
JOHN NAPIER.
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