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in ice. The value of the felted boxes from a sanitary point of view is to be found in the possibility of providing poor mechanics and laborers with warm food. By portable contrivances it will be easy to keep food warm for some hours, and the advantages to poor workmen cannot be overestimated. To the rich it also insures thoroughly cooked food, while even by them the economy will not be despised. At the Paris Exhibition of 1867 these felted boxes in the Norwegian department attracted a good deal of attention. They were shown in actual operation, and an opportunity was afforded of tasting food that had been kept in them for some hours."
At a recent meeting of the French Academy of Science, a report was presented from the committee appointed to inquire into the alleged insalubrity attending the use of cast-iron stoves. Extensive experiments had been made, and the results arrived at were, first, that all heating apparatus made of metal, and all stoves made of cast iron, give off, while in use, a large quantity of carbonic acid ; second, that the quantity of that gas given off from stoves of plate iron was often insignificantly small; third, that the carbonic acid contained in the air was readily converted into carbonic oxide, by coming into contact with thoroughly redhot stoves; and, fourth, that the oxide of carbon thus generated may, especially in confined localities, become very injurious to health. To obviate all bad effects, the committee recommend that cast-iron stoves be lined inside with fire-brick, and enveloped outside with a casing of sheet iron, so arranged as to leave space for free circulation of air in communication with a well-drawing chimney.
ON A NEW METHOD OF BREAD-MAKING." Baron Liebig has just made some important researches on a new method of bread-making. He remarks on the stationary character of this art, which remains to the present day much in the state in which it was thousands of years ago. He dwells upon the sanitary importance of the mineral constituents of grain, and the necessity of a sufficiently abundant supply of them in bread. These are best found in certain kinds of black and brown bread, which are, therefore, more wholesome than the white bread that is nevertheless preferred by most people (especially by the lower orders), on account of its better appearance and superior palatableness. The problem has hence arisen, how to provide a beautiful white bread which shall contain all the essential mineral constituents of black bread. These mineral constituents (phosphate of potash, lime, magnesia, and iron) are introduced into the bread by the use of the baking-powder'invented by Professor Horsford, of Cambridge, in North America. This baking powder consists of two powders, – the one acid, the other alkaline. The acid powder is phosphoric acid in combination with lime and magnesia; the alkaline powder is bicarbonate of soda. Two measures made of tinned iron, the larger one for the acid powder and the smaller one for the alkali, are employed. When bread is required to be made, every pound of four is mixed with a measure of the acid powder and a measure of the alkali powder, and sufficient water added to make dough, which is presently made into loaves and baked. In one and a half to two hours bread may be made by this process.
The chemical change which takes place will be easily intelligible; carbonic acid is generated and phosphate of the alkali is formed at the same time. The essential feature in Horsford's invention is the economical getting of phosphoric acid in the shape of a dry, white powder. This is done by taking bones, burning them, and then treating the well-burnt bone-earth (which consists of phosphate of lime and magnesia) with a certain quantity of sulphuric acid, so as to remove two-thirds of the lime, and leave a soluble superphosphate of lime. The sulphate of lime which results from the action of the sulphuric acid is separated from the rest by filtration, and the solution subsequently concentrated by evaporation, and, when it becomes very concentrated, mixed with a certain quantity of flour, and dried up. The mixture of flour with the superphosphate admits of being reduced to the finest powder, and constitutes the acid powder just referred to. It will be observed that the alkali powder contains soda, whereas potash is required, in order to furnish the right kind of mineral salts. Liebig proposes to rectify this defect by using a certain quantity of chloride of potassium along with the alkali. Chloride of potassium is now tolerably cheap, owing to the finding of immense quantities of it at Stassfurt. - British Medical Journal.
M. Revoil, an architect well known in France, from having the charge of the restoration of the Roman remains at Montpellier, Toulan, Nimes, has recently been engaged in a special study of the early architecture of the southern provinces of the ancient kingdom. In the course of his attempts to arrive at exactitude of definition, by the aid, at one time, of the camera lucida, and at another, of the telescope, he has been induced to make experiments as to the combination of the principles of the two instruments. The result of this effort M. Revoil has called the Téléiconograph.
The principle of this instrument is that of allowing the image transmitted by the object-glass of a telescope to pass through a prism connected with the eye-piece. The rays of light that would, in the ordinary use of the telescope, be transmitted direct to the eye, are refracted by this prism, and thrown down upon a table placed below the eye-piece. The distance between the prism and the table determines the size of the image projected on the latter, and it is easy for the observer to trace on a paper placed on this sketching-table the actual outlines indicated by the refracted light.
The idea once grasped, it is easy to work out the details. The telescope is placed on a stand with screws and clamps, allowing of both horizontal and vertical motion, as it may often be necessary to give traverse to the instrument in order to make a connected drawing of a larger area than can be included in the object-glass at one view. In fact, an entire panorama can be traced, if the relative position of the axis of the telescope and the surface of the sketching-table are undisturbed.
We see no reason to doubt that M. Revoil's eye-piece might be adapted to the ordinary theodolite, so that any person who possesses one of these instruments may, at a small expense, obtain a good sketching apparatus.
The advantages possessed by the téléiconograph over the camera lucida are manifest. The size of the image may be determined at will by the person who uses the former, without any diminution of accuracy. We have before us a lithograph of the summit of one of the towers of Notre Dame de Paris. The “ croquis” was taken by means of the instrument of M. Revoil, at the distance of about 300 metres. It is 12 inches long. A sketch, taken by the aid of a camera lucida, is drawn alongside, and is only one inch in length, or one-twelfth part of the linear measure of the bold outline of the teleiconogram (as we suppose the new likeness will be called.) Two mountain-peaks, in Provence, sketched by aid of the same apparatus, show how admirably it can be applied to the sketching of country. For the purpose of military surveying its services promise to be of the utmost value.
The teleiconograph insures certitude in drawing, but it does not draw. It is an aid to the artist, not a self-acting substitute for his eye and hand. The sharp, bold touch of a master of the art of drawing will be as distinct from the feeble peddling of an inferior workman, when the refracting prism is used, as when freehand sketching is resorted to. The division of attention between the object and the copy, which is often so painful, will be entirely avoided by the use of this instrument. In the hands of a true artist the result will be every way admirable, exact as a photograph, without the distortion of all those parts of the field which are distant from the centre, and at the same time marked by all the peculiarity of touch proper to the master. The camera lucida, from its greater portability, will still hold its own; but we shall hope to see M. Revoil's instrument brought into familiar use in this country, to meet circumstances for which it is peculiarly adapted. - Builder, July 17.
METHOD OF DETECTING POISONOUS GASES. THE GASOPHANER. The 66
Pioneer,” England, states that a discovery has been made by an officer, which, if the results on a large scale are at all commensurate with the experiments made on a small one, may prove of great value in giving a timely indication of the approach or presence of that poisonous state of the atmosphere which is generally believed to precede cholera and other epidemic diseases.
The gasophaners, or poisonous gas indicators, as the discov
erer calls them, are easily and cheaply made. A piece of fused toracic acid, the size of a walnut, from which the water of crystailization has been expelled, is heated to redness in chlorine, or has dissolved in it while hot a small quantity of common salt, care being taken that there is not sufficient soda-16 per cent.-to convert the boracic acid into borax, which would spoil the effect. The red-hot lump of boracic acid thus charged is blown with a common glass-blower's tube into a thin glass ball or bulb, about the size of a small hand-lamp shade, and the gasophaner is ready for
When first made, the glass is clear, with beautiful irridescent colors, due partly to the thinness of its sides; but left for a time, shorter or longer, according to the amount of moisture in the atmosphere, in normal breathing air, it becomes covered or clouded with a light-blue film (due chiefly to the carbonic acid gas of atmosphere), which, combined with the irridescent colors beneath, has an opaline or pearly lustre. On bringing the clouded gasophaner carefully to the flame of a spirit-lamp, this film instantaneously vanishes, leaving the glass of that part again clear and shining; . The delicacy of this test is so great that, although by breathing on the newly-made gas the film may be much more rapidly formed than by mere exposure to the atmosphere, an approach to the spirit-lamp flame will no longer drive off the carbonated compound formed, on account of the impure gases contained in breath. At the same time, carbonates thus formed from the breath of a child, or of an extremely healthy person, vanish precisely as the aerial ones do on application of gentle heat. Held over a solution of ammonia, the air carbonate will not form, except on the upper part, where the ammoniacal gas has less action; but if held so that the breath may mix with the ammoniacal gas, a thick white cloud of carbonate of ammonia without opaline lustre covers the gasophaner. This cannot be driven off by heat, but froths up on an approach being made to the lamp flame. But the most remarkable indication given by the gasophaner is when it is held over a solution of sulphuretted hydrogen. The gasophaner immediately becomes pitted, as it were, with small-pox on the surface next the gas; and these spots, on being examined with a microscope, are found to be round, radiated crystals, the centre or nucleus of which soon bursts into a hole. They are white by transmitted, and dark brown by reflected, light. Nitride of boron gave exactly similar crystals as the chloride, and so did pure boracic acid. These crystals, therefore, are presumed to indicate a combination of boron with hydrogen, a fact hitherto unknown to chemists. The gasophaner can be reheated and reblown as often as required.
UNIFORMITY OF WEIGHTS AND COINS.
Professor Leone Levi, at the meeting of the British Association, read the report of the committee on Uniformity of Weights and Coins in the interest of Science." The report commenced by stating that considerable progress has been made during the year in the assimilation of weights, measures, and coins in different countries. The North German Confederation of 1868 adopted the metre is the basis of measures and weights, and resolved to take as the primary standard measure of length the platinum bar in possession of the Prussian government. This bar is equal to 1.000 0301 metre at the temperature of melting ice. Metre weighits and measures are made legal in the United States, and are employed in post-office exchanges with foreign countries. It were much to be desired that our post office would follow the good example. Still greater progress had been made in the introduction of the metrical system into India, — with regard to which the report entered into particulars. Efforts had been made to promote the adoption of the same system in the colonies. The second report of the royal commission had lately recommended the removal of every difficulty, and the full and legal introduction of the metric system. Chambers of Agriculture and Commerce (including the Barnstable Farmers' Club) had petitioned Parliament in favor of a uniform system of weights and measures. With respect to international coinage no further step had been taken since the report of the royal commission. The Chancellor of the Exchequer had, however, recently enunciated his views in favor of imposing a seignorage of about one per cent. for coining gold into sovereigns. This was a difficult question, and the committee contented themselves with echoing the recommendation of the royal commission, that another international congress be speedily held to consider the scheme. In conclusion, the report recommended the reappointment of the committee for the purpose of further stimulating the early realization of a uniform system of weights, measures, and coins in all countries.
NEW OXYGEN PROCESS.
Oxygen procured cheaply and easily, is, as we have often said, a very desirable thing. The numerous applications that could be made of it are so evident that we need not stop to mention them, but we lay before our readers yet another plan, and this time an ingenious one, for obtaining it. The mineral sources of oxygen being comparatively expensive, MM. Montmagnon and Delaire have betaken themselves to that cheap reservoir, our atmosphere, and have further availed themselves of the discriminative action of wood charcoal and water, or certain saline solutions. We give here, it must be understood, the figures of the authors named, without checking them by a reference to the figures of Dr. Angus Smith, who has made most careful experiments on the absorptive action of charcoal. According, then, to our authors, 100 litres of fresh wood-charcoal will, when exposed to atmospheric air, occlude 925 litres of oxygen, but only 705 litres of nitrogen. Now, it would appear that when the charcoal so saturated with gas is thoroughly saturated with water, there will be expelled 650 litres of nitrogen, but only 350 litres of oxygen. Thus we have now left in the pores of the charcoal 575 litres of