In order to prevent that inconvenient, unhealthy process of manufacture, the Société d'Encouragement of Paris proposed a premium for a chemical process enabling the manufacturers of these articles to dispense with putrid fermentation. The process suggested by Mons. Labarraque, the successful candidate, is remarkable for its cheapness and the facility of its application. In following the method recommended by this chemist, these animal matters can be worked more easily, and kept for a longer time without evolving any noxious smell.

The guts, previously scoured, are put into a vat containing, for every forty guts, four gallons of water, to which 14 pounds oxychloride of sodium, marking 13° on the areometer of Beaumé, is added. After twelve hours of maceration, the mucous membrane is easily detached, and the guts are free from any bad smell; by this method, the process of insufflation is more easily performed.

The insufflated guts are suspended in a dry room until the desiccation is complete; and, once dried, the extremities by which they were tied together are cut, and, in pressing the hand over the length of the insufflated (inflated) gut, the air inside is completely taken out. The guts are then submitted to fumigation by sulphur, in order to bleach and to preserve them from the attacks of insects. After this last operation, the guts are fit for use.

Besides a large home supply of bladders, England imports several hundred thousand a year, packed in salt and pickle, from America and the Continent; and the aggregate value of the bladders used in Great Britain, is stated at £40,000 or £50,000.

NEW METHOD OF PREPARING GUNPOWDER.

Mr. W. Bennett, of England, has invented a new method of manufacturing gunpowder, the ingredients consisting of lime, nitre, sulphur, and charcoal; the lime is dissolved in a sufficient quantity of water to bring the other elements into a paste. The lime, after having been made into a solution, is strained through a fine sieve; this solution is then added to the other ingredients, and the whole is put into a mill, and ground until it becomes a paste; it is then taken out of the mill, and passed between two rollers, one grooved and the other plain. The paste, by passing between the rollers, is formed into long strips of a triangular shape; it is then carried on an endless web or canvas over some hot tubes, which are heated by steam, hot water, or any other artificial heat which may be applied; by this means, the strips are easily broken into grains. This mode of manufacture prevents a great deal of danger, as the powder is pulverized and brought into grain while in a wet state. The lime makes a firm grain, resists the damp, and gives it a degree of lightness which increases the bulk 25 per cent. over ordinary gunpowder, —a great advantage for blasting purposes. Plaster of Paris, Roman or Portland cement, or other strong cementing substance, may be used as a substitute for lime. And the patentee finds that for blasting purposes the following proportions answer well, that is to say, nitre, 65 lbs.; charcoal, 18 lbs.; sulphur, 10 lbs.; and lime, 7 lbs.; but the proportions may be varied according to the strength required.

THE CONSTRUCTION OF SAFES.

The following is an abstract of a series of highly interesting and important researches recently made by Prof. E. N. Horsford, of Cambridge, Mass., on the "Construction of Safes," intended for protection against fire, dampness, rust, and frost:

Protection against Fire.-The experience of the last few years has practically demonstrated, what might have been foreseen, that protection against fire can be relative only, not absolute. Fire-proof buildings, so called, yield, when stored with combustible materials and for a long time surrounded by flame. The best of fire-proof safes are destroyed, when exposed to heat sufficiently intense and prolonged. This being admitted, how shall the largest practical measure of protection against fire be secured? First. By placing the books, papers, etc., to be preserved, in an incombustible enclosure, as of iron. Second. By surrounding the books, etc., by a non-conductor of heat. Third, and chiefly, by interposing between the incombustible enclosure, or outer iron shell, and the wooden case containing the valuables, a substance which on the approach of fire, is converted into vapor, absorbing the heat and carrying it away.

If the second and third be omitted, the contents of the safe will be destroyed as soon as the iron enclosure has become sufficiently hot to set them on fire. If the third only has been omitted, the power of preservation will be proportioned to the thickness of the layer of nonconducting material; and this, at the best, is relatively but for a brief period. If the second, only, has been omitted, since the protection arising from vaporization is due to the absorption of heat in converting liquid or solid substances into vapor, it will obviously be proportioned to the quantity of substance so converted into vapor. A hundred pounds of water will absorb twice as much heat in passing off in the form of steam, as fifty pounds will; and a safe that contains one hundred pounds of water to be evaporated, will preserve its contents in safety, through a fire in which a safe containing but fifty pounds would be destroyed. A safe will then, manifestly, be a better protection against fire, in proportion as it unites within it, an incombustible shell, the best non-conductor, with the largest amount of liquid or solid to be converted into vapor, at a temperature not dangerous to the contents of the safe.

Dampness. Injuries from dampness in safes are not unfrequently of a most serious character; such as the mildew, and disintegration of papers, writings, &c. These injuries arise from the transmission of water from the fire-resisting composition, through cracks imperfectly closed at the time of manufacture, or made subsequently by rusting; or through the pores of the wooden case; or by the freezing of the water of the composition, by the expansion of which the walls are separated from each other, and communication established between the filling and the chamber of the safe. They may be prevented by so constructing the safe as absolutely to prevent any communication of water or vapor between the filling of the safe and the books and papers.

In a climate like ours, a safe may be exposed occasionally to temperatures below freezing. Any of the safes, as at present constructed, cannot contain any considerable quantity of water above that in chem

ical combination, without the danger of bursting by cold. This opening of the seams of the safe at once exposes the contents of the case to the exhalation of moisture from the filling. The protection against this kind of injury manifestly lies in such construction of the safe as will provide for the expansion consequent on freezing, without opening the joints or seams of the various parts.

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Rust. This is one of the agencies by which communication between the filling and the chamber of the safe is effected after the lapse of time; and by which the contents of the chamber become damp. It may be prevented by consuming the oxygen of the air which would otherwise act on the iron. Chemical compositions are prepared which will, by absorbing the oxygen, perfectly protect the iron from corrosion or rust, even in the presence of air and water.

Varieties of Safes in use. -The safes at present in use differ from each other in various respects, but chiefly in the capacity of the composition employed, to yield vapor.

The earliest safes were designed chiefly to protect treasure against burglary, and were distinguished for their strength. Next came safes having non-conducting walls as protection against fire. In 1840, a safe appeared which took advantage of the principle of vaporization of water as protection against fire. The alum safe, upon the same principle was devised in 1843. The gypsum safe, also on the same principle, has long been in use. The cement safe, in which hydraulic cement is substituted for gypsum, has been many years in use. In the English safe of Milner, invented in 1840, the space between the iron shell and wooden case is occupied with closed tubes containing water, these tubes being imbedded in saw dust. On exposure to fire, the tubes burst, and the water, flowing into the sawdust, is converted into vapor, and escapes through the joints of the iron shell.

In the alum safe, invented by Messrs. Tann, of England, and a modification of which is produced in this country, the vapor is derived from the water of crystallization of the alum. Twenty per cent. of the weight of the alum is converted into vapor at 212°, and eighteen more at 250°. The remainder is given up only at a heat destructive to the contents of the safe.

goes out at 212°.

In the ordinary gypsum safes, the surplus water added in the mixing, if it does not remain to do injury by charging the case and books with dampness, or by freezing, is in process of time exhaled until there remains only what has entered into chemical combination. This latter amounts to twenty per cent. Of this, ten per cent. is given up at 212°, and half of the remainder below 300°. The cement safes, as they are usually prepared, contain, after setting, and after time for giving up the surplus water, about six per cent. of water. Of this, one per cent. As the Alum safes are prepared in this country, the alum is mixed with pipe clay, and this mixture with fragments of brick, the former to absorb the water as the alum melts and to facilitate the vaporization; the latter to give support and prevent the composition from falling when the alum melts. The proportion of alum is about one quarter of the whole. This would give of water from the composition, at 2120, only five per cent., and at 250°, four and a half per cent. more, or only nine and a half in all. If the alum were raised to the proportion of one half of the whole mixture, it would give up but

ten per cent. of water at 2120, and nine more at 250°, or only nineteen per cent. at temperatures not dangerous to the contents of the safe.

In most fires the exposure is for so brief a period that the protection in some of the best safes is adequate; but there is the constant possibility that the fire may be too powerful and too protracted for the composition employed, and the protection consequently inadequate.

Can this protection against fires be increased?-The incombustible inclosure is of wrought iron, and nothing could be better than this. The points, therefore, remaining for consideration are, What is the best practicable non-conductor? and, What is the best composition for keeping down heat for vaporization?"

In answer to the first question, experiments were made, among other materials, with Infusorial Earth; a mixture of Sal Soda and Gypsum ; a mixture of Glaubers Salt and Gypsum; set Cement; Alum and dry Cement; Gypsum with Gelatine.

A wrought-iron cup, containing about eight ounces of water, was filled with each substance in its turn, and the bulb of a thermometer imbedded to the same distance from the bottom in all. The vessel and its contents were then subjected to the same degree of heat. The conducting power, or the facility of heating throughout, was measured by the number of degrees swept over by the ascending column of mercury in successive minutes. The range of heat was from 220° to 572°. Infusorial earth was heated 27° in one minute.

Sal soda and gypsum taken in equal parts, 14° in one minute., Glaubers salt and gypsum, taken in equal parts, 12° in one minute. Cement, set and dried, 11° in one minute.

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Potash alum, 3 oz. 5° per minute, from 220° to 300°. Dry cement, 6 oz. 4° per minute, from 300° to 572°. Gypsum, 6 oz., and water, 6 oz., 2° per min. from 220° to 300°. with 3 per cent. of gelatine, 4° per min. from 300° to 572°. From each, the water due to a temperature of 212°, had, as already intimated, been driven out. In the cement, alum, and gypsum, there remained water in combination. The infusorial earth proved the best conductor, and would of course be the poorest substance for filling a safe. Of all, the gypsum and gelatine, as prepared for this experiment, throughout the range in which the contents of the safe are secure against fire, namely, below 300°, affords the best protection, so far as conduction is concerned. It is, indeed, difficult to conceive of a substance better suited for non-conduction than this mass of set plaster and gelatine, after the surplus water alternating with every particle of gypsum has been driven out, leaving behind an infinity of minute cavities, rendering the whole porous and non-conducting to the last degree.

How shall this quality be combined most advantageously with the second requisite mentioned above, that of supplying matter to be vaporized, thereby carrying the heat away?

Two sets of experiments were undertaken to determine this point. The first on a small scale, the second on a large and more practical scale. The first was conducted at the same time with the series already detailed, and employing the same apparatus. The wrought-iron cup was filled with each mixture in turn, supported at a constant altitude over a flame of uniform height, and the thermometer imbedded to the same depth in all."

The results showed, that, as regards protection to be afforded by vaporization from 212° to 220°, the following substances ranked in value in the order stated:-Gypsum, gelatine, and water; Cement; Glaubers salt and gypsum; Sal soda and gypsum; Alum.

The question of using a composition which should give up vapor at a temperature above 212° only, was tested in the use of a mixture of sulphate of ammonia and common salt, diluted with powdered coke, which, on the application of heat, yielded sal ammoniac. Experiments were also made with a mixture of ammonia-alum and common salt, diluted, like the above, with coke. This yielded water in addition to sal ammoniac. Clay and powdered brick were substituted for coke. They gave results inferior to all except the potash-alum.

In addition to these laboratory experiments, a series were undertaken on a scale of such magnitude as to render the results of more direct practical value. As the object was to determine the relative excellence of different kinds of safes in which all the circumstances of exposure were the same, it was conducted with great attention to details, and was, on many accounts, the most important ever made of which any record has been preserved.

Experiments in Reverberatory Furnaces.-Five wrought-iron safes were constructed, each of one cubic foot capacity. For each, a small wooden box four inches in the clear, and three-quarters of an inch in thickness, was prepared to represent the inside case. When in place, there was a space for composition of three inches thickness on every side of the box. In each wooden box was placed a piece of parchment, some white writing paper, cotton batting, a piece of sealing-wax, a selfregistering thermometer ranging to 600°, and a series of small thermometers bursting at given temperatures.

No. 1 contained sulphate of ammonia, 15.5 lbs. ; common salt, 15.5 lbs. ; powdered coke, 24 lbs.; wooden box, 2 lbs.; iron shell, 27 lbs. Total, 84 lbs.

No. 2 contained potash-alum, 26 lbs. ; pipe-clay, 26 lbs.; brick, 28 lbs. ; dry cement, to fill, 2 lbs.; wooden box, 2 lbs.; iron shell, 283 lbs. Total, 1124 lbs.

No. 3 contained ammonia-alum, 26 lbs.; common salt, 13 lbs. ; coke, 16 lbs.; wooden box 2 lbs. ; iron shell, 294 lbs. Total, 874 lbs. No. 4 contained cement, 60 lbs.; water, 193 lbs.; soapstone front, 9 Ibs.; wooden box, 2 lbs. ; iron shell, 30 lbs. Total, 1203 lbs.

No. 5 contained plaster of Paris, 50 lbs.; water, 21 lbs.; dry cement, to fill, 9 lbs.; wooden box, 2 lbs. ; iron shell, 28 lbs. Total, 110 lbs. These safes were carefully introduced into a reverberatory furnace from which a discharge of twenty thousand pounds of molten iron had just taken place, and when the walls were nearly at the temperature of melted iron. The safes were placed on the bottom of the furnace, the door closed, and after adjusting the draft so as to permit the furnace to cool slowly down in the usual way, the safes were left from five o'clock in the afternoon till ten the next morning.

On taking the safes from the furnace, they were first weighed. No. 1 had lost 8 lbs.; No. 2, 153; No. 3,2 163; No. 4, 13; No. 5, 16.

1 This is the common alum safe, except that one-third of alum was employed instead of one-quarter.

2 One pound of this, and of each of the preceding two, is due to the charring of the wooden box.