Rags are a marketable commodity, and command fixed prices according to their quality. As with all articles of commerce, t|iese prices are governed in a measure by the mercantile law of supply and demand. As foreign rags are sold at a less price than the American article, and the consumption in the United States is considerably greater than the supply of the latter, large quantities are imported from Europe. The larger proportion of foreign rags that find their way to our Atlantic cities, are exported from Bremen, Hamburgh, Rostock, Ancona, Messina, Leghorn, Palermo, and Trieste. They arrive in our ports in closely packed bales, containing each about four hundred pounds, which, according to their respective qualities are branded S. P. F. F., S. P. F., F. F., F. X., and F. B. There are many varieties, even in these divisions, and their qualities afford very clear indications of the state of comfort and cleanliness of the particular localities from whence they were originally gathered. The rags of England and the United States are generally clean, and require but little washing and cleansing before they are ground into pulp ; the Italian rags, on the contrary, are originally so dirty that they require to be washed in lime before they are fit for use. The greater portion of the rags from the north of Europe are so dark in their color and so coarse in their texture that one naturally wonders how they could have formed part of any t*(ly woman's garments ; while those, on the other hand, which are collected in England, Scotland, and the United States, appear evidently to have belonged to a people much better clad. Having thus alluded to the material employed in paper making, the reader's attention will now be directed to the process of its manufacture. The visitor to a regularly organized paper mill is first conducted to THE BAG ROOM. The initial process of sorting the rags is conducted in a long room, in which from twenty to thirty women are employed in sorting, dusting, and cutting them. Each woman stands at a frame or table, the top of which is covered with a net-work of wire, through which to admit ih?i dust ; on her left is a quantity of rags conveniently placed, on her right is a box divided into three compartments. On a part of the table an upright knife is fixed for cutting the rags into suitable lengths. As it is the business of the woman to sort and cut the rags, she spreads a certain quantity on the wire frame, and as she shakes them a great deal of the dirt passes through the interstices of the wire into a box beneath. Those pieces that require to be cut she draws across the blade of the knife, by which it is instantly divided. All seams are thrown out, as the sewing thread, unless thoroughly ground, would produce filaments in the paper. These are afterwards picked out by children, and again find their way to the woman's table. The work of sorting and cutting rage is performed with great rapidity. When cut, sorted, and dusted, the rags are weighed into bags of a hundred pounds each and conveyed to THE BOILING AND WASHIJsG ROOM. Here they are placed into large square chests or vats, in which steam is admitted from below and boiled with lime for a few hours. From the boiling room they are conducted in suitable vessels to an upper room in the mill, where they are emptied into troughs or cisterns, several of which are ranged in a row ; these troughs and the machinery within them, are technically called engines, and are used for washing the rags, The troughs are usually ten feet long, four arid a half feel broad, apd two and a half feet deep, and are made of wood lined with lead. In each trough an iron cylinder 33| inches in diameter and 26 inches wide is fitted ; pure water is conveyed by means of a pipe or tube into the trough a few inches from the top, and another tube connects with the lower pari for carrying off the soiled water. The cylinder being set in motion by means of steam or water power, about a hundred weight of rags are dumped in, as before mentioned, and as much water introduced as will raise the whole to within an inch or two of the brim. Into the cylinder is fixed a numbei of knives at given distances apart, projecting a little more than an inch from its axis; and beneath the roller is a plate ii which is also attached a number of knives. When the cylin der commences its revolutions, of which it is made to make about 160 per minute, the rags are carried with great rapiditj through the knives ; and as the cylinder is depressed or ele vated, the rags are bruised or cut as may be required. Above he cylinder is a cover made of a wire frame communicating vith the pipe which admits the pure water. When, tliere-bre, the whole mass is in agitation, the rags, after passing hrough the knives of the cylinder and plate are carried up in inclined plane in the trough and the foul water is carried )ff througk the waste pipe below ; in this way the rags are ;ut bruised, and washed. After the above opei-ation is continued for a sufficient time, he water is let off and the cleansed mass is removed to a )ress for the purpose of driving out the greater part of the vater. They then undergo the process of BLEACHING, This process reduces all descriptions of rags to a uniform vhiteness, and requires to be so conducted as not to injure the quality of the fabric. On being removed from the press the ags are placed in a receiver, or chamber made of wood, from vhich the external air is carefully excluded. Into this chamber are conveyed pipes communicating with a retort, in which I chemical chlorine is formed by the application of heat to a iue proportion of manganese, common salt, and sulphuric icid. This part of the process is completed in a few hours, riie rags are now white, but they have an intolerable smell, lo remove this, and to preserve them from being injured through the effects of the bleaching, they undergo a secorici process of washing and braising which entirely purifies them. Prom the washing engine the rags are conveyed to the beating engine, which is constructed similar to the other except that the knives on the cylinder and plate are closer togtither, and the former revolves with greater rapidity. Havino- been ground for several hours in this machine, the rags assume the beautiful appearance of pulp technically calltd "stuli?' It should here be remarked that all paper manufacturers do not use the same materials for bltiiiching the rags." In several large paper mills a substitute for manganese is used. This is 1 mixture of phosphates of lime and soda ash,which seems to mswer the required purpose,and is much less expensive. The 3ame may be said of the whole prescribed formtilee in jmyvv making. So rapid are the strides of scientific progress, that 3re a useful practical theory is put in full operation, new improvements are suggested, which, in many cav.cB, iivo made to supersede it. Hence, no description of this extensive branch )f art will fully rcpresjiit every manufacturer's method. The 3ssential features, however, of the processes employed in paper making, are similar in all paper mills. As what is technically called " machine-made paper " is a comparatively late invention, it may properly be expcjcfced ihat this keatise should preface any remarks upon the sul)-iect with a brief description of HAND MADE PAPER. Until a little more than half a century since all descriptions jf paper were made by hand. The process though silraple is very beautiful, and evinces a remarkable degree of mechanical ingenuity. We have already described the various stages the rags have gone through up to the time they are reduced to a pulp. From this pulp or " stuff," which is about the consistency of pure milk, and resembling it in appearance, paper is made. The stuff is first poured into a vat, at the bottom of which is a copper vessel made to fit exactly within it for the purpose of keeping the stuff warm. This warmth is communicated by means of heat supplied by a steam pipe from below. The workman forming the sheet, who is called a " vat-man," is provided with two molds. These are slight frames of wood, covered with a fine wire cloth. Fitting to each mold is a dekle or movable raised edging which determines the size of the sheet. The vatman, putting the dekle on one of the molds, dips it vertically into the stuff, find bringing it to the surface horizontally, covered with pulp—which, to preserve an equal consistency is kept in a state of agitation in the vat—and shakes it gently so that all xarts of the wire frame shall be equally covered with it. This operation requires a great deal of nicety, both in determining the required thickness of the sheet and in producing it of a uniform thickness throughout. The vatman then pushes the mold with the incipient sheet to his fellow workman, who is called a " couch er," and carefully taking off the dekle applies it to the second mold, and proceeds as before. The coucher, who receives the first mold, having a pile of porous pieces of flannel by his side (called "felt"), turns the mold carefully over upon one of these, and upon which the sheet remains, having been detached from the mold ; he then places a felt on the sheet and is ready to turn over another from the second mold. Thus the vatman and the coucher proceed, only two persons being required at each vat, the one molding a sheet of paper and the other placing it upon the felt, until a certain quantity its made, when the pile of felts is subjected to the iiction of a powerful press. The sheets, after this pressure is completed, have acquired sufficient consistency to enable them to be again pressed by themselves. They are next parted, then dried; next sized in a mucilage, to give them greater body and strength, and again dried and pressed, and finally counted into quires and reams. Any number of vats, each requiring the servicjs of two men, may be used at the same time. This is a matter, however, usually regulated by the capacity of the mill and the means of the manufacturer. MACHINE MADE PAPER. As previously intimated, the progress of mechanical science of late years, in paper making as in many other branches of art, has been so rapid in its onward inarch that manual labor is in a great measure superseded by machinery. In paper making, machinery is not only a saving of manual labor, but economizes time and money, and largely mulliplies the facilities for its manufacture, as will be made plainly manifest to the most indiflerent observer. The process of converting a thin pulp into paper by machinery is a rapid though complicated operation. In the 179 whole range of labor-saving machinery there is perhaps no series of contrivances which so forcibly address themselves to the senses ; and yet, with all its intricate and wonderful operations, there is nothing mysterious in it, as the spectator can see and comprehend its workings from the beginning to the end. At one extremity of the machine is a large chest which is kept full of pulp, and through which a wooden cylinder with fan-shaped projections attached, is kept revolving to keep the fibers of rags, which resemble pure snow flakes, perpetually moving, and consequently equally suspended in the the water which contains them. At the bottom of the chest is a cock through which a continuous stream of pulp flows into a vat placed below it, which is always kept fllled to a certain hight. This pulp flows through a narrow wire sieve, situated in the upper part of the vat, and is also kept in motion to make the sifting process the more complete. Having passed through the sieve the pulp flows through a pipe in the vat still onward to a ledge, over which it falls in a regular stream, like a sheet of water over a smooth dam; here it is caught upon a plane which presents an uninterrupted surface of flve or six feet, upon which it is evenly spread. This plane is constanly moving onwards with a gradual pace, and has also a shaking motion from side to side. This plane is composed of an endless web of the flnest wke very closely woven together. The pulp does not flow over the sides of the plane because of a strap on each side, which is kept moving and passing upon its edges, and which regulates the width of the paper. After passing the wheels where these straps terminate, the paper is sufiiciently formed not to require any further boundary to deflne its size. The pulp at this stage has ceased to be a fluid though the paper is till tender and wet. When it quits the plane of wire the paper passes over a large cylinder covered with felt, upon another plane also covered with felt, which moves onward the same as the wire plane. This felt surface is also endless, being united at the extremities like a towel upon rollers. It now travels up an inclined plane of felt, which gradually absorbs its moisture, when it is seized between two rollers which powerfully squeeze it. From thence it travels up another plane of felt and through a second pair of pressing rollers. The paper up to this point is quite formed but it is fragile and still damp ; from these it is received upon a small roller, and is guided by this over the polished surface of a large heated cylinder. The soft tissue now begins to smoke and the paper commences to harden. From this cylinder or drum, it is received upon a second, considerably larger and much hotter than the flrst; as it rolls over the polished gurface of the drum all the roughness of its appearance when in the cloth region gradually vanishes. At length having passed over a third cylinder, still hotter than the second, and having been subjected to the pressure of a blanket which conflnes it on one side, while th5 cylinder smoothes it on the other, it is caught upon the last cylinder, which passes it over to the reel, upon which it is wound in a flnished state but in an endless roll. It has now to be cut into required lengths so as to form the size of the sheet. This is done in a supplementary machine which receives it ofl of the reel, and by means of a circular knife it is cut into the requisite lengths. The paper is counted into quires and reams, folded double, and Subjected to a certain pressure, so that it may pack close for marketable purposes. From the commencement of the process, when the pulp flrst flows into the wire web until the paper into which it is formed is received upon the reel, a little less than two minutes is occupied. The web of wire travels at a rate which produces twenty-flve superflcial feet of paper per minute. In a machine the thickness of the paper is regulated by the quantity of stufi* which is allowed to flow out of the chest ; and all that is required to render the thickness invariable is an invariable speed in the motion of the machine. If the web of wire travels at a rate that will form twenty-flve feet of paper per minute, and the chest discharges flve gallons of pulp in the same period, there can be no change in the thickness of the sheet; but let the machine move at greater speed, say at the rate of twenty-flve per minute, while the discharges are but five gallons, and the paper will be thinner by one fifth. Again, let the pace of the wire plane be unaltered, and the chest discharge ten instead of five gallons per minute, and the sheet will be just double the thickness. In conclusion it should be remarked that the process of converting rags into pulp is the same with machine-made as with hand-made paper, except that in the former it is conducted on a more extensive scale. A hundred years ago rags were made into pulp, first by washing them by hand and then by placing* them in close vessels until they became half rotten, and afi,er the fiber was nearly destroyed they were reduced to pulp either by hammering in a mortar or by a cylinder grinding against the sides of a circular wooden bowl. These operations were slow, expensive, and very destructive to material; and yet, crude as the method was, it existed for centuries, and so continued up to the period when science stepped in to enlighten mankind with its manifold wonders.. Portable Boilers. At the Steam Users' Association monthly meeting, held at Manchester—Mr. W. Fairbairn, President, in the chair—Mr. L. E. Fletcher, chief engineer, said that the increasing number of boilers used for steam crane and other similar purposes, renders it important that any dangerous defects to which these boilers are liable should be generally known. The explosion of these boilers has become by no means un-frequent, and as they are now constantly used in the erection of public buildings, and sometimes in close proximity to crowded thoroughfares, the subject becomes of increasing importance. The boiler in question was of the internally- fired vertical class, cylindrical i n the external casing, as well as in the internal fire-box, and domed on the top, while the flames from the fire-box pass ofl* to the chimney through a single central uptake tube, which formed a most important tie between the crown of the flre-box aiid that of the external casing. Boilers of this type are very simple in construction, and well calculated when new to resist a high pressure, so that they are very generally adopted. The dimensions of the one under consideration were : Height, 8 ft. 9 in.; diameter, 3 ft. 6 in. in the external shell, and 3 ft. 9 in, in the flre-box ; while the thickness of the plates was -j-th. in., and the load on the safety-valve, per square inch, 70 lb. The defect to which it is now wished to call attention, was a deep groove or furrow running entirely round the inner casing of the flre-box at the bottom of the water space, and eating into the metal to a depth varying from to j-th in., so that more than"half the strength of the plate was gone. This is not a peculiar case ; others very similar havd been met with, and* especial danger arises from the fact that these grooves are very diflScult to detect. They take place so low in the water space as to be very nearly, if not entirely, concealed by the blocking ring at the bottom, while the only opportunity of examining them is through one or two small sight holes cut through the outer casing. It is frequently supposed that because boilers are small therefore they are safe, whereas the fact of their being small makes them dangerous. Small boilers cannot be inspected as larger ones can, since they do not admit of access for a man, and, therefore, they are to a greater or less extent apt to be worked on at a risk. The internal examination, and thus the safety, of portable boilers is a question which hitherto has not received that consideration which it deserves, but the subject should no longer be neglected. It is well worthy of the attention of engineers to endeavor to construct such portable boilers as are too small to admit of a man's getting inside, so that they may be taken to pieces for examination; and it becomes imperative either that arrangements should be made for doing this, or that these boilers should not be allowed to work on for more than three or flve years without being cut open for exMnina-tion, whatever the inconvenience might be. No doubt if the attention of engineers were directed to this subject, inventive talent would soon construct boilers that could without much difficulty be taken to pieces so as to be examined internally, and thus their safety ensured.