Chapter 4

The ground floor comprises a large entrance hall or vestibule, 40 ft. by 44 ft., forming, with the cloakroom, the principal staircase, the rooms for the concierge, and the area, the whole front of the building. This large vestibule is vaulted over by means of one of the systems of cement armé to be described. The floor is constructed on another similar system, and will be paved with mosaic work. The ground floor of the courtyard will be occupied by the conference hall, 50 ft. by 50 ft., to hold 300 seats. An annex, 50 ft. by 20 ft., adjoining this hall, will open on the same by a large arched bay, and may be separated from the larger hall by means of a special system of wooden soundproof roller shutters. The floor of the large hall will be a movable one, to be raised or lowered by an ingenious system of hydraulics, and capable of being placed in an inclined position for conference meetings, or raised to a horizontal position for ball room purposes.

The entresol floor will comprise a large room for meeting, smoking and conversation rooms, and a reading room, to be used as a club for the members of the society. The first floor will contain the offices of the society, a large committee room, and all conveniences. The second floor will be devoted entirely to the purposes of the important library, comprising the library proper, a room 45 ft. by 25 ft. by 17 ft. high, rising to the ceiling of the low story above, and lighted by a large semicircular bay at either end: the surrounding rooms of the height of the second floor will be destined for the librarian, catalogues, drawing office, and library offices. The third floor will be devoted entirely to the purpose of storing the books of the library, in low rooms communicating by means of the gallery overlooking the library below, which will be crossed by means of a light, iron bridge. The bookcases will be suspended from the upper floor, and will be arranged in vertical tiers hung on rollers, after the system employed at the British Museum. The roof story will be divided up into an apartment for the chief secretary, and reached by a private staircase from the ground floor. The large basement, occupying the whole of the ground surface of the building, will be used for storing the records of the society, and will contain the heating apparatus, stores, etc. A hydraulic lift will afford access to the landings of each floor. The chief feature of the façade, which is simple in style, is the wide arched bay, 24 ft. across, rising from the pavement to above the cornice; this bay will be filled in with an open decorative framework of wrought and cast iron.

Some of the most interesting points of the construction, besides the large use of iron, are the systems employed in the construction of the floor. The ground floor is built after the Coignet system, composed of light iron bars and cement; the first floor and its supporting pillars and arches is constructed after the Hennebique system of cement armé; the upper floors are formed of iron joists, filled in either with the system of light supports and plaster, much employed at Paris, or with terracotta fillings between joints. The roof is lined internally with agglomerated cork bricks, affording protection from excessive heat or cold, and the walls of the area will be lined with opaline, a vitreous material of a bluish white color, which in this case will insure cleanliness, and afford additional light; the lavatories and water closets will also be lined with the same material.

Speaking of the Hennebique system of cement armé, employed for the arches and floor of the first story, it will be interesting to illustrate the method by a few sketches, explaining the theory of this system, which has been put to practical proofs in a large number of buildings, chiefly for industrial purposes, in the north of France. The perspective section will give an idea of the construction as employed in the building for the civil engineers, a system which holds its ground well against its rivals of other methods of cement armé.--The Building News.

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BELLEEK CHINA.

Belleek porcelain (frequently pronounced "Bleak" by those who do not know the derivation of the name) is a thin eggshell ware of great lightness and translucency, characterized by a creamy, or sometimes grayish, tint, and usually covered with a delicate pearly or lustrous glaze. It is in reality a variety of Parian ware, being formed in the same manner by the process called casting, or pouring diluted clay or slip of the consistency of cream into plaster moulds, which, by absorbing a part of the moisture from the portion of the liquid preparation in direct contact, retain a thin shell of partially dried clay after the superfluous contents are taken out. After standing a few minutes the thin cast can be liberated from the mould. The thickness of the walls, of course, depends upon the length of time the slip is allowed to remain in the mould before the surplus is removed. By this ingenious method cups, saucers and other forms of ware can be made almost as thin as an egg shell or a piece of heavy paper, and after being allowed to become thoroughly dry can be safely burned in the kiln. It can readily be understood that it would not be possible to make such fragile pieces by the usual processes with plastic clay, which must be of the consistency of putty or dough, on the potter's wheel or by pressing in moulds.

Belleek ware was first made at Stoke upon Trent by the eminent potter William Henry Goss, who invented the body or composition some thirty-five years ago; but it was not then known by this name. Soon after its introduction Messrs. McBirney & Armstrong induced some of Mr. Goss' workmen, including his manager, William Bromley, to join them at their porcelain works, then recently started (in 1863) in the town of Belleek, County Fermanagh, Ireland, and the art was established so successfully there that the name of the village was given to the ware which has since become so noted. The distinguishing characteristic of this beautiful product is its lustrous glazing, which varies in form from white to yellow and through graded tints to a dark leaden hue.

Mr. Goss has continued to manufacture this dainty variety of porcelain until the present time, and his factory has become one of the most noted in the British empire. Among the most popular of his productions in this body are loving cups and little cream jugs, cups and saucers, and fairy tea sets embellished with beautifully colored crests and coats of arms of the different English cities and of prominent personages, such as Queen Elizabeth, Sir Walter Raleigh, King Henry of Navarre, Queen Victoria, the Prince of Wales, Shakespeare, Sir Walter Scott, and Robert Burns.

Of more interest, perhaps, to Americans are the porcelain tumblers which have just been produced at the same factory, bearing on the front a faithful duplication in blue and yellow enamels of the insignia of the society of Sons of the Revolution, which were made at the suggestion of a member of the society in Pennsylvania. The soft, satiny Belleek body seems to be particularly well adapted to show off to advantage the rich designs of these badges, and this suggestion will doubtless be followed by other patriotic hereditary societies in the United States.

John Hart Brewer, of Trenton, first attempted the manufacture of Belleek ware in this country. He commenced his experiments in this line in 1882, and in the following year brought over from England William Bromley and his son from the Belleek works in Ireland. Subsequently the elder Bromley joined the Willets Manufacturing Company, of the same place, and introduced the manufacture of eggshell porcelain there, and at the present time there are no less than five or six establishments in Trenton where the same class of ware is made.

Among many specialties recently introduced is a new style of decoration which has been worked out by Miss Kate Sears, a Kansas girl who studied modeling in Boston. Going to Trenton for the purpose of pursuing her studies in this direction, one day in 1891, while engaged in working over the wet Belleek, the idea of carving delicate designs in the dry clay occurred to her, and after conducting a series of experiments her efforts were crowned with success. The process of modeling which Miss Sears has originated is as follows: A vase or other piece which has been formed in the wet clay and dried is taken before it has been in the kiln, and with knives or other tools the design is cut or chiseled so as to leave the background as thin and transparent as possible when finished. As the dry Belleek, besides being thin, is extremely brittle, and crumbles easily, the carving is an exceedingly difficult operation. It is necessarily a very slow process, since at any moment the knife is liable to cut through the wall and ruin the piece.

The result of this process is a clear cut, chiseled effect, which cannot be obtained by moulding or casting, a moonlight effect of fairy like character, most beautiful in conception, and possessing marked originality. While sometimes several weeks are consumed in executing a single piece of the carved ware, Miss Sears has produced a large number of such designs, each one of which is a perfect work of art, reflecting credit upon the artist and the manufacturers.

The marks which appear on the various productions of Belleek porcelain are of considerable interest to collectors and admirers of this beautiful ware. Mr. Gross has adopted as a factory mark his family crest, a falcon rising ducally gorged, which is printed on each piece in black. The mark of the Belleek factory in Ireland, consists of the four Irish emblems, the watch tower, the hound, the harp of Erin, and the shamrock, and is printed on the ware in green or black. At the Etruria Pottery, formerly operated by Messrs. Ott & Brewer, now known as the Cook Pottery Company, the mark used on Belleek ware was a crescent bearing the name with the initials of the proprietors, "O. & B." The Willets Manufacturing Company uses for a factory mark on its decorated Belleek pieces the figure of a serpent looped in the form of a W, which is printed in red. On similar ware produced by the Ceramic Art Company is printed in red a design composed of a painter's palette and a circle inclosing the monogram C. A. C., while Messrs. Morris and Willmore, of the Columbian Art Pottery, employ a shield with the initials of the firm name, M. W.

The manufacture of Belleek ware was introduced into this country by English potters who had learned the processes at the potteries in England and Ireland, and we cannot, therefore, lay claim to originality so far as the product itself is concerned; yet, in a measure, the ware as made in America differs materially from the foreign in many respects, and has been developed in new directions, so that it has come to have distinctive characteristics of its own which entitle it to be ranked with original American productions. While our potters, perhaps, have not yet reached the high degree of elaborate modeling which characterizes some of the imported Belleek, they have already surpassed the foreign manufacturers in the simplicity and elegance of their forms and the artistic quality of their decorations, while in delicacy of coloring, in the excellence and lightness of body, the American products are not surpassed. A visit to the showrooms of the Trenton potteries will prove a revelation to those who still believe that no artistic china is made in this country.--Edwin Atlee Barber, in China, Glass and Lamps.

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GOODMAN'S HATCHET PLANIMETERS.

The instrument we are about to describe is an improvement on the hatchet planimeter and is due to Prof. Goodman, of Leeds. One form of the instrument is intended for the measurement of areas of surfaces, and the other form for the measurement of the mean height of a figure such as an indicator diagram.

London Engineering, to which we are indebted for the cuts and copy, describes the instruments as follows: The method of using the two instruments is practically the same, but for the present we shall confine our remarks to the instrument for measuring areas. In order to familiarize oneself with the peculiar action of the instrument, it will be well to get a large sheet of paper on a drawing board or a large blotting pad, and holding the instrument vertical to the paper, grasp the tracing leg very lightly indeed between the forefinger and thumb of the right hand, with the hatchet toward the left hand, as shown in Fig. 1. Then by moving the tracing point round and round an imaginary figure and allowing the hatchet to go where it pleases, it will be seen that the hatchet moves to and fro along zigzag lines, and travels sideways--the side travel being nearly proportional to the area of the figure described by the tracing point. If the tracing point be too tightly grasped, the hatchet will not move freely, and, will have a side slip. When this occurs the side travel of the hatchet ceases to be proportional to the area traced out. A loose weight is hung on the hatchet to prevent this side slip, but as soon as a little skill is attained in the use of the instrument, this weight may be dispensed with.

When measuring the area of such a surface as that inclosed by the boundary line shown in Fig. 3, a point, A, is chosen somewhat near the center of the figure; the exact position is, however, immaterial. From the point, A, a line, AB, is drawn in any direction to the boundary; the tracing point of the planimeter is now placed at A, with the hatchet at X, Fig. 3, that is, with the instrument roughly square with AB. The hatchet is now lightly pressed in order to mark its position on the paper by making a slight dent, then leaving the hatchet free to move as shown in Fig. 1, the tracing point is caused to traverse the line, AB, and the boundary line in a clockwise direction, as shown by the arrows, returning to A via AB. The hatchet will now be found to have taken up a new position, Y, which must be marked by again pressing the hatchet to make a slight dent in the paper. If the figure under measurement be on a separate sheet of paper, the paper must now be revolved about the point, A, through about 180 deg. (by eye), using the tracing point of the instrument as a center, care being taken that neither the point nor the hatchet be shifted while the paper is being turned. The line, AB, will again be roughly at right angles to the instrument, but in the reverse direction (see dotted lines in Fig. 3). Again cause the tracing point to traverse the line, AB, and the boundary line as before, but this time in a contra-clockwise direction. The hatchet after this backward motion will take up the new position, X1, which may or may not coincide with X; if not, prick a central point between X and X1, as shown, then, of course, the distance of this point from Y is the mean side shift of the hatchet; this distance measured from the zero of the scale on the back of the instrument is the area of the figure in square inches. The scale is read in exactly the same manner as a geometrical scale on a drawing, the whole numbers being read to the right of the zero and the decimals to the left. The instrument does not profess to give results nearer than one-tenth of a square inch.

In some cases on large maps, for example, the figure cannot be turned round as indicated above; in that case the instrument itself must be turned round through 180° and two fresh dents, X¹Y¹, obtained; the area of the figure is then the mean of the two readings, XY and X¹Y¹.

When the area is large the instrument will move through a large angle, and consequently, if square with AB to start with, it will be considerably out of square at the finish. In such a case it is only necessary to see that the mean position of the instrument is square with AB.

By carefully examining the scale it will be observed (see Fig. 1) that the divisions are not equal, but that they gradually increase from zero upward; herein consists the improvement of this instrument over the ordinary hatchet planimeter invented by Knudsen, of Copenhagen, who shows in a pamphlet published by him that

c1 + c2 I = ------------- p [1 - (R / 2p)²] 2

Where I = the area traced out by the pointer in square inches.

c1 = the distance between the dents, X and Y, in inches.

c2 = the distance between the dents, X1 and Y, in inches.

p = the length of the instrument from center of hatchet to point in inches.

R² = the mean square of the radii of the figure.

The making of such a calculation for every area measured is, of course, quite out of the question. The labor involved would be as great as calculating the area by the ordinate or by Simpson's method; hence it is usual to neglect that part of the formula inclosed within the square brackets, which amounts to assuming the area to be equal to the product of the mean side shift of the hatchet by the length of the instrument; this, however, involves an error too big to be neglected, and, moreover, one that is not a constant fraction of the area measured, thus:

Area of circle, square inches. 10 20 30 40 Error per cent. 0.8 1.6 2.4 3.2

These errors are, however, compensated for in Goodman's improved instrument by making the scale with constantly and regularly increasing divisions. If, however, the area dealt with be not a circle, the error involved in assuming that its R² is equal to the R² of a circle of equal area is so small that it is quite inappreciable on a scale which only reads to one-tenth of a square inch. If the R² for any given area were say 5 per cent. greater than that of the equivalent circle, the error involved would be 0.0016 of the whole quantity when measuring an area of 40 square niches, or 0.064 square inch, a quantity which cannot be measured on the scale. It has been proposed to use a roller and vernier to enable the readings between the dents to be measured with a greater degree of accuracy, but it will be readily seen that the instrument is not reliable to the second place of decimals, hence such refinements are only imaginary. Even with this special scale that we have described above, the inventor does not profess to get as good results as with an Amsler planimeter; he regards his instrument as equivalent to a foot rule in comparison with a micrometric gage as representing Amsler's instrument; but for a great number of purposes the foot rule is sufficiently accurate, and only when great accuracy is required will a micrometer be used, so with the two forms of planimeter. The rougher instrument has some advantages, however; there are no delicate moving parts to get out of order, and the cost is but one-fourth.

In order to ascertain the relative accuracy of various methods of measuring areas, Prof. Goodman has had a large number of irregular areas measured by his first year students within a week or so of their entering the department, before they have attained to any degree of skill in using instruments. The results were as follows. Amsler's planimeter was taken as the standard, the area measured by it being independently checked by an assistant.

Measurement of Areas Method. Reduced to 100. Amsler planimeter 100 Goodman " 100 + or - 0.6 Simpson's rule 100 + or - 1.0 Mean ordinates 100 + or - 2.4 Cutting out in cardboard and weighing against piece of known area 100 + or - 4.4 Equalizing curved edges by drawing straight lines along boundary and calculating by triangles 100 + or - 7.0

In the averaging instrument for getting mean heights of figures, the length of the instrument between the hatchet and the pointer is variable. The length is set to the length of the diagram (see Fig. 2); it is then used in precisely the same manner as the planimeter described above. From what we have already said, our diagram in Fig. 5 will be perfectly clear. The mean distance between the dents is in this case the mean height of the diagram, measured on an ordinary scale, or the mean pressure in the case of an indicator diagram measured on a scale to suit the indicator spring.

Knudsen's formula given above applies equally well to this averaging instrument. Neglecting for the moment the quantity in the square brackets, we have I = c p where c = (c1 + c2)/2 but we also have I = h l where h is the mean height and l the length of the figure, therefore h l = c p; but in this instrument we make p = l. Hence h = c, or the mean height of the figure is equal to the mean distance between the dents. The quantity in the brackets is too great to be neglected, however. If we were always dealing with circles, the ratio (R/2p)² would be a constant, and numerically equal to 1/16 or 6.25 per cent. Then all we should have to do would be to use a scale 6.25 per cent. longer than the true scale. But with a long narrow figure such as an indicator diagram, this ratio is much smaller. The measurement of a large number of diagrams gave a mean value of 1/60 for diagrams 4 in. long. It is obvious that, if a diagram be shortened, this ratio will increase, for the value of R does not decrease as rapidly as p, and vice versa; hence this ratio varies approximately inversely as the length of the diagram. Taking the value of 1/60 for the 4 in. diagram, this is equivalent to saying that there is an error of 1 in 60, or 1.67 per cent., in the result, and from the formula it will be seen that the result is too great by this amount; hence, if we make the length, l, between the legs of the instrument 1.67 per cent. of 4 in., or 0.067 in. less than the length from the tracing point to the center of the hatchet, p, we shall compensate for the error on a diagram 4 in. long. But the ratio of this constant quantity 0.067 in. to the length of the diagram also varies inversely as the length in just the same manner as the ratio R/2p, hence this method of correcting the instrument is approximately right for all lengths of diagrams. It must be remembered that if this correction were entirely neglected, it would not exceed two per cent.; hence any inaccuracy in this correction is an exceedingly small quantity, well under 1 per cent.

Whenever errors have been attributed to the instrument, on examination it has always been found that they were due to carelessness in setting the length to the diagram, or to the tracing leg having been grasped so tightly as to cause side slip.

The accuracy of the instrument may be easily demonstrated by drawing a rectangle, say about 4 in. long and 2 in. high, and finding the mean height by the averager, then by doubling the paper over and comparing its height with the mean distance between the dents, it will be found that they agree if the instrument has been carefully used.

In many quarters we know that there is a great deal of prejudice against instruments of this kind. We are quite sure, however, that if only draughtsmen and others would spend half an hour in trying them over, they would save themselves many hours of tedious labor in calculating areas by methods which are seldom as accurate as the results obtained by a planimeter in the same number of minutes.

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APPARATUS FOR THE MANUFACTURE OF ACETYLENE GAS.

We give herewith, from Le Genie Civil, illustrations and brief descriptions of some of the more prominent apparatus used for the manufacture of acetylene gas.