public in the pulpit of Westminster Abbey on the day following his death.

"Life is a serious thing,' as Schiller says," he writes, quoting the motto to his own book "Past and Present" in sending a copy of it to Thomas Cooper, "and as you yourself practically know. These are the words of a serious man about it." This deeply rooted and ever-present conviction explained much of the contempt for modern verse which he was never tired of proclaiming and reiterating in his published writings, in his letters, and in his conversation.

Of the earlier portraits of him, three are specially interesting: first, the full-length sketch by "Croquis" (Daniel Maclise) which formed one of the Fraser Gallery of portraits, and was published in the magazine in June 1833. The original sketch of this is now deposited in the Forster Collection at South Kensington. The next is a sketch by Count D'Orsay, published by Mitchell in 1839. The third, which was the great author's own favourite among the early portraits, is a sketch by Samuel Lawrence, engraved in Horne's "New Spirit of the Age," published in 1844. Since the art of photography came into vogue, a series of photographs of various degrees of merit and success have been executed by Messrs. Elliott and Fry, and by Watkins. The late Mrs. Cameron also produced a photograph of him in her peculiar style, but it was not so effective or successful as her fine portrait of Tennyson. An oil-painting by Mr. Watts exhibited some fifteen years ago, and now also forming part of the Forster Collection at South Kensington, is remarkable for its weird wildness; but it gave great displeasure to the old philosopher himself a displeasure which I once heard him express in no measured terms. More lately, we have a remarkable portrait by Legros and an admirable one by Mr. Whistler, who has seized the tout ensemble of his illustrious sitter's character and costume in a wonderful manner. The terra cotta statue by Mr. Boehm, exhibited at the Royal Academy in 1875, has received such merited meed of enthusiastic praise from Mr. Ruskin that it needs no added praise of ours. It has been excellently photographed from two points of view by Mr. Hedderly of Chelsea.

One of the best and most effective of the many likenesses of Mr. Carlyle that appeared during the last decade of his life was a sketch by Mrs. Allingham-a picture as well as a portrait-representing the venerable philosopher in a long and picturesque dressing-gown, seated on a chair and poring over a folio, in the garden at the back of the quaint old house at Chelsea, which will henceforth, as long as VOL, CCL. NO. 1803.

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it stands, be associated with his memory. Beside him on the grass lies a long clay pipe (a churchwarden) which he has been smoking in the sweet morning air. So that altogether, as far as pictorial, graphic, and photographic art can go, the features, form, and bodily semblance of Carlyle will be as well known to future generations as they are to ourselves. And this, in his opinion (that is, the preserving of the features of the noble, the wise, the brave, and the good), was the only worthy and proper function of the painter's art. All the rest he looked on as mere dilettantism.

The impression of his brilliant and eloquent talk, though it will probably remain, for at least half a century to come, more or less vivid to some of those of the new generation who were privileged to hear it, will, of course, gradually fade away. But it seems hardly probable that the rich legacy of his long roll of writings-historical, biographical, critical-can be regarded as other than a permanent one in which each succeeding generation will find fresh delight and instruction. The series of vivid pictures he has left behind in his "French Revolution," in his "Cromwell," in his "Frederick," can hardly become obsolete or cease to be attractive; nor is such power of word-painting likely soon to be equalled or ever to be surpassed. The salt of humour that savours nearly all he wrote (that lambent humour that lightens and plays over the grimmest and sternest of his pages) will also serve to keep his writings fresh and readable. Many of his dicta and opinions will doubtless be more and more called in question, especially in those of his works which are more directly of a didactic than a narrative character, and in regard to subjects which he was by habit, by mental constitution, and by that prejudice from which the greatest can never wholly free themselves, incapable of judging-such, for instance, as the scope and functions of painting and the fine arts generally, the value of modern poetry, or the working of Constitutional and Parliamentary institutions.

RICHARD HERNE SHEPHERD.

371

IN

SCIENCE NOTES.

SMOKELESS FIRES AND GAS COMPANIES.

N my last month's note on Mr. Scott Moncrieff's project for supplying towns with smokeless fuel, I referred to the probable difficulty of withdrawing the coke, from which only one-third of the volatile constituents have been distilled. Since that was written experiments have been made and this difficulty encountered. It appears to have been considerable; but, as it is mechanical, it may be overcome by mechanical ingenuity. Mr. Moncrieff's original proposition was to extract only one-third of the gases and vapours. If one-half were taken the difficulty would be diminished, and the principle of his scheme might be still carried out, especially if combined with that of Dr. Siemens to the extent of using gas for lighting the fire and reviving it when desired.

I have done what is equivalent to this by simply attaching one of Fletcher's solid-flame burners to a flexible tube and placing it under the grate of an open American stove in my study, using as fuel a mixture of coke and ordinary coal. It answers admirably. In five minutes the fire is fully lighted, and I can regulate it to the weather by using much, or little, or no gas afterwards.

A holder of gas shares has objected to my strictures on the monopoly of the London gas companies. The answer to his and all other arguments that have been or may be used in defence of such companies is the simple fact that most of the great towns of the midland and northern counties of England have abolished the gas companies by purchasing their plant and monopoly rights at very high prices, and are now supplying themselves with far better and cheaper gas than they received from the gas companies, at the same time paying off both interest and principal of the money borrowed for the purchase. In many cases they make a considerable profit besides this, and are debating whether to use it in reduction of the local rates or to lower still further the price of gas. The latter seems to be generally preferred, and will be carried out as soon as additional plant is erected for supplying the additional demand that lower prices will create.

As the by-products now pay for the gas at the works, its prime

cost when it reaches our houses being simply that of storing and conveying it to us; the economising of reservoirs, mains, pipes, &c., is of primary importance. While we only use it for lighting purposes, these reservoirs, pipes, &c., are idle during the day; but once the price of gas is lowered sufficiently to render it as cheap a fuel as coal, we shall keep these mains, &c., profitably at work all day long, to the great advantage of all concerned. This consummation is so devoutly to be desired, that, if the London gas companies attain it sooner than it is reached by the gas-making corporations of the Midland and the North, nobody will desire them to be superseded. But if, on the other hand, the system of great towns co-operating to supply themselves with their own gas continues to prove its superiority to the present London system, it is not likely that the metropolis of the world will consent to remain behind the other towns of England in the supply of such primary necessaries of life as heat, and light, and cleanly air.

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THE FORMATION OF FOGS AND CLOUDS.

VALUABLE contribution to the physical history of fogs, mists, and clouds has been recently made in a communication by Mr. John Aitken to the Royal Society of Edinburgh, a society that is far too much overshadowed by the Royal Society of London. He used two large glass receivers, one filled with ordinary air and the other with filtered air, the filtration being effected by passing it through cotton wool, which removes even the finest particles of dust. Into these he passed equal quantities of steam. In the unfiltered air the steam assumed the usual well-known cloudy form, in the filtered air it remained transparent.

From this it appears that aqueous vapour does not condense into cloud matter, or vesicular vapour," as it has been called, unless it is supplied with some sort of solid nuclei upon which the water may be deposited. We all know what happens when we supply a large nucleus, such as a bottle of iced water in a warm room. In this case the amount of condensation is due to the lower temperature of the bottle cooling the film of air immediately surrounding it, and diminishing its capacity for retaining vapour. This film of air thus becomes super-saturated with steam, which it deposits on the bottle.

The air in both of Mr. Aitken's receivers was super-saturated, but in spite of this remained clear when it contained no solid surfaces upon which the steam could condense. I presume that condensation did occur on the surface of the receiver itself.

Water behaves similarly in passing from the liquid to the solid state. Pure clear water standing in a smooth vessel may be cooled down considerably below its freezing point, but immediately upon the introduction of a solid nucleus, such as a grain of sand or anything angular, crystals of ice are formed on and around the solid nucleus, and the temperature of the whole rises to the ordinary freezing point. Super-saturated solutions of crystalline salts act in like manner, sulphate of soda notably so.

Mr. Aitken infers that a fog or a cloud or mist is an accumulation of minute solid particles coated with an extremely thin film of water. Other experiments lead him to conclude that when there is much dust in the air, but little vapour condenses on each particle, and thus all may continue floating; but if the proportion of dust to condensible vapour is small, each particle condenses so much that it more readily falls as rain.

According to these experiments, there would be no fogs, no clouds, and probably no rain if there were no dust, but instead of these the super-saturated air would deposit its vapour as heavy dew on the surface of every solid body upon the earth. All clouds, fogs, mists, every puff of steam escaping into the air, and the visible condensation of our breath in cold weather, are indications of the dusty state of our atmosphere. This dustiness is indicated by other investigations. Piazzi Smyth, in 1856, erected a temporary observatory on the Peak of Teneriffe, at a height of 10,700 feet above the level of the sea, but the dust-haze which interferes with telescopic work was still there, though much was left below.

The sources of dust were examined by Mr. Aitken, and in the course of this investigation it appeared that the chief fog-producing particles are those which are not large enough to form the visible motes of the sunbeam, but are far finer and quite beyond the reach of human vision. He found that if pieces of glass, iron, brass, &c., were heated in air that had been filtered, they introduced clouds of dust producing a dense fog, and that this source of dust (or what Mr. Aitken calls dust) is so effective that one hundredth of a grain of iron thus heated will produce a distinct cloudiness in the experimental receiver. Many different substances were thus tried, and all were found to be fog-producers.

The visible motes of the air may be destroyed by burning them with a gas flame; such a flame does not destroy the fog-producing particles, but on the contrary produces them, as was shown by burning gas in a receiver supplied with filtered air. The products of combustion of pure air and dustless gas gave an intensely fogproducing atmosphere.