Chambers's Journal of Popular Literature, Science, and Art, fifth series, no. 126, vol. III, May 29, 1886

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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