parent vapour. But in doing this an amount of heat will be rendered latent (ie. deprived of its existence as temperature) which would be sufficient, if directly applied and concentrated upon the solid portion of the earth, to raise its surface above the fusion-point of granite.'

Besides the heat that would be rendered latent by evaporation, a further demand would be made by the arctic and antarctic iceaccumulations and those above the Alpine snow-line. These must go before a great rise of general temperature can occur; for while they remain they spread cold air currents over the earth's surface far beyond their own boundaries.

But this is not all. The vapour added to the atmosphere would form a veil of additional resistance to the transmission of the solar heat rays. It would greatly increase the density of our clouds and mists, maintaining such atmospheric conditions as we now experience at the opening of 1882.

Summing up all these considerations, I venture to conclude that if the comet. of 1880, or any other comet, should presently shower its contents into the sun, its utmost effect upon us here in England will be an improvement of the harvests of the succeeding years, and upon our neighbours a little farther south a fuller ripening of their grapes, justifying the old tradition concerning "comet vintages."

THE POLYTECHNIC OF THE FUTURE.

'HEN I wrote the Note on the Polytechnic in last October

WHEN number of this Magazine, a regard for vested interests pre

vented me from going beyond a mere allusion to the requirements of the future, but now I am at liberty to speak plainly and fully.

The old Polytechnic, though admirably adapted to the requirements of such a Society as that for which it has lately been purchased, is too small to meet the present requirements of our vastly extended metropolis.

The demand for a great Metropolitan Hall of Popular Science is now far greater than ever. The members of the old Polytechnic staff who maintained that "Science don't pay," that purely scientific lectures and demonstrations will not "draw" in these days unless spiced or Peppered with theatrical entertainments, made all their calculations on the narrow basis of the old building.

My one month's experience prior to the Directors' resolution to

1 The data upon which these conclusions are based will be found all together in small space in the XIXth Chapter of my Simple Treatise on Heat. Note particularly Regnault's Table on page 146, and that I inch of mercury is equal to 13 inches of water. Also the climatic action of water, page 170.

wind up, brought out the depressing fact that the cost of providing scientific lectures and demonstrations of quality and magnitude commensurate with the present-day demand, and of advertising these as other London shows are now advertised, would amount to more than could be covered by filling the hall and theatre with all the paying visitors they could accommodate over and above the free list.

On this account, I urged several leaders of the Temperance movement to take it up as a place of rational recreation for the abstainers. It is big enough for a section of the community who have within themselves their own special means of easy advertisement.

It is now purchased by or for (I do not know which) "The Young Men's Christian Institute," and is admirably adapted for such a Society; but for the great metropolis and its myriads of visitors, another, a far larger and more magnificent, Hall of Science is demanded.

As regards the building, nothing has yet been invented more suitable than an ordinary play-house. It should be as large as Drury Lane or Covent Garden Theatres-one of these would do well; but if such a theatre be bought, the first necessary step to be taken is the radical demolition of all the scenery, scene-shifting machinery, dressing-rooms and everything requisite for stage-plays, lest the sad history of the old place be repeated.

The stage space of a theatre would serve as a hall for scientific models and exhibits, and for a promenade that could be cut off when necessary by the drop-scene, duly whitewashed to serve as a screen for dissolving views and microscopic illustrations.

Such a theatre and hall ought to be made to supply, for the million, what the Royal Institution now so admirably provides for the "Upper Ten ;" and, provided it resisted all dramatic seductions, and adhered to sound though popular science as firmly as the Royal Institution, the London Institution, the Society of Arts, &c., have done, it might be as successful as they are, on a much larger scale, with low admission fees, if popular scientific lectures and demonstration of the highest class, and of a magnitude worthy of the metropolis of the world, were supplied.

M.

THE PHILOSOPHY OF MANURING.

LADUREAU describes the results of the action of those farmers in the North of France who return to the soil all that remains after separating the sugar from the beet. being composed of only carbon and the elements

Pure sugar, of water, is

obtained by the plant entirely at the expense of the atmosphere, from the carbonic acid and water which it supplies.

Therefore land may be cropped for sugar for an indefinite length of time without exhaustion, provided everything else but the sugar is returned to it. The beet plant, as a whole, exhausts the soil upon which it grows, as does the sugar cane, taking away certain minera compounds that must somehow be returned, in order that it shall retain its undiminished fitness for this particular crop.

This is so simple and self-evident that it scarcely appears possible that it need be taught to those who are interested in the subject. Nevertheless, the want of a knowledge of this simple principle has nearly ruined some of the West Indian sugar plantations. The old practice was to use the canes as fuel in boiling down the syrup, and the ashes of these canes, i.e. the purely mineral matters which they had obtained from the soil, were left to be washed away by the rains, when, by simply spreading them on the soil, they would have supplied, in the most concentrated possible form, just the manure which the soil demanded for the particular business of sugar-growing.

But we need not go so far as the West Indies to discover manifestations of this particular form of ignorance. In an ordinary garden, especially an amateur or ornamental garden, the amount of crop actually taken away for use forms a very small fraction of the total weight of the vegetable matter growing on the ground. Such a garden, once fairly started, demands no more than a restitution of the mineral matter contained in the crop consumed, provided all the weeds and all the unused stalks and leaves are honestly returned to the soil from which they were taken.

I have had more than twenty years' experience in amateur gardening-mainly utilitarian-have moved about a good deal, and thus have cultivated many different gardens. All have been remark. able for their abundant crops, though I have never purchased a single load of manure, while my neighbours have carted in ton after ton, and obtained smaller edible crops than mine. I do not even waste the ammonia and the agricultural fuel of my weeds by burning them, but bury them whole, and with them the pea-stalks, beanstalks, cabbage-stalks, &c. &c. Thus buried, they undergo during the winter slow combustion, warm the soil, and supply it with humus, at the same time giving up their ammoniacal salts to this humus and to the absorbent alumina of the clay, which supply it in the summer to the succeeding crops.

These weeds, &c., with the addition of the vegetable refuse of a small household, and the well-burned coal-ashes (ie. the mineral

matter of fossil vegetation), I have found sufficient to maintain and increase the fertility of a kitchen garden and orchard covering more than an acre.

At the same time, I see the gardeners employed by my neighbours wheeling away barrow-loads of weeds to pitch them on waste ground, if any is at hand, and the dustman carrying away cartloads of vegetable treasures. Then, on the day following, or thereabouts, cartloads of expensive and offensive manure are brought to the same doors from which far better material was thrown away the day before.

Stable manure and cattle-stall manure are especially valuable for farm land, simply because they carry back to the hay-field and the oat-field precisely that which has been taken away. But the salts removed by garden weeds differ materially from those contained in hay and straw litter, or oats and horse-beans, and thus the unscientific gardener who uses these requires at least half a ton to be as effective as one hundredweight of the decayed produce of the garden itself.

IT

GASES PASSING THROUGH SOLIDS.

Tis not generally known that certain metals are readily permeable by certain gases, though it has long been known to scientific investigators. Iron, for example, when red-hot, is but a sieve in relation to hydrogen and carbonic oxide.

Everybody knows that an ill-constructed close stove, i.e. a stove that can possibly become red-hot at its sides, vitiates the atmosphere, but the cause of this is not so generally understood. It has been attributed to the drying of the air, and vases of water have been placed on such stoves to compensate this by evaporation. It has also been attributed to the burning of particles of dust and fibre floating in the air; but the real source of the actual mischief is the passage of carbonic oxide gas through the red-hot iron of the stovewalls. This carbonic oxide, or imperfectly burned carbon, is quite different from the carbonic acid formed by complete combustion of carbon. The latter is suffocating when sufficiently abundant, but not poisonous, while the former is an irritant poison even in very small quantities.

Mr. J. B. Hannay has recently shown that even glass, when heated to 200° C. (= 392° Fahr.), absorbs large quantities of oxygen and carbonic acid at high pressures, the gases apparently becoming fixed within the solid; but to what extent they may be given out again, or pass airly through, remains to be further tested.

W. MATTIEU WILLIAMS,

IN

TABLE TALK.

AN ECCENTRIC BOOKSELLER.

N some future edition of "English Eccentrics" a place should be reserved for old Sams, the once well-known bookseller. So many years have elapsed since the old man died, that it will shortly be too late to gather any particulars concerning him. My own recollections are now becoming misty, and a shadowy outline is all that remains of a figure that used once to be distinct and familiar. Among book-buyers, however, particulars concerning this strange being may yet be gleaned, and it is partly with a view to eliciting these that I supply my few remaining recollections.

When I first encountered Sams, he occupied the shop in the market-place at Darlington in which he died. The impression I preserve of him is that of a tall, venerable-looking man in a Quakerlike costume of rusty black and with black gaiters. This was about 1850-55, when I was still a young man, and as such but indifferently observant, at least of any one belonging to my own sex. Sams had a decided stoop, a lean, pinched, and scholarly face, and long white hair. In that curious old shop, with its two low windows, one on each side of the door, old Sams kept a collection of books such as no bookseller out of London could rival. Here were folio Shakespeares and Chaucers galore, with Caxtons, Wynkyn de Wordes, and Pynsons enough to make the bibliophile's mouth water. Woe, however, to the ignorant and confiding purchaser who trusted to Sams' plausible speeches and the manuscript notices in front of his volumes. If ever it was necessary to take to heart the sage counsel caveat emptor, it was when his shop was entered. In those days, as in these, bibliographical knowledge was in very few hands. Aware of this fact, Sams did not hesitate to make up his books in a fashion that puts to shame the bungling attempts in the same direction of some modern booksellers. I was early, if vainly, put on my guard. Having on my first visit bought of Sams what professed to be a copy of Pynson's edition of Barclay's "Ship of Fooles," and discovered that the bulk of the volume was made up from the much inferior edition of Cawood, I learned to investigate closely Mr.