CHAPTER XIV EXPERIMENTS IN THE COMPRESSION OF SHEETS OF DIFFERENT SUBSTANCES BY CONVERGING PRESSURE APPLIED AT THE EDGES THE FORMATION OF DOMED ANTICLINALS EXPE XPERIMENT No. 10.-Preliminary to the actual compression of sheets into domed structures, with the object of elucidating the movements and flow of material that must take place in their formation, I took a piece of apron linen and cut out a circle 9 inches in diameter. The problem I set myself was to reduce the periphery to 8 inches diameter. With material such as cloth the only possible mode of reducing the circle is by folding at the edges, the tendency being to force up a quasi-dome formed of radial anticlines. An examination of Plate VIII., fig. 1, p. 150, will show that in this case I reduced the circular area covered by the linen cloth from 9 inches to 8 inches diameter by folding at the periphery in four places, the folds being pinned down to the board. This reduced the area covered by the cloth from 81 circular inches to 64 circular inches, which formed the area of the base of the intended dome. These folds, being all in one direction, created a series of four radial curved anticlinals, meeting near the centre, and forming there an irregular domical centre which measured about 2 inches in vertical height. The illustration explains itself and shows the form a non-rigid sheet will take in adapting itself to the new conditions of space. It is this sort of folding by which drapery adapts itself to the movements of the human body in an infinite variety of ways, to the delight of the sculptor, who rejoices in the beauty of form which it discloses though it clothes. Experiment No. 11.-The next material experimented with was what is called 'cork carpet.' It is a pliable material, possessing a limited compressibility, and also capable of a little stretching without rupture. The thickness of the material was in this case a full quarter of an inch. Out of this Mr. M. Treleaven Reade cut a circle 5 inches in diameter, which was planted upon a board. Wire nails were driven into the board just touching the periphery of the circle, and then bent down so as to claw the periphery down to the board. The circle was compressed by a screwcramp, and a second ring of nails driven in, the cramp being moved round the circle as the operation went on, the nails being clawed down as before. The photograph, Plate VIII., fig. 2, p. 150, shows this. The advantage of this process, besides its simplicity, is that the model retains its form, which it would not do if a compressing machine without holding-down nails were used. The result was the arching up of a very perfect dome having a diameter at the base of 4.62 inches, or a reduction of area from 25 circular inches to 21.39 inches. The height of the dome was 87 inch. This proved a very interesting experiment; it showed that the tendency to fold at the periphery being prevented by the clawing down of the nails was compensated by compression of the peripheral area. I may add that the resultant dome was immensely strong. Experiment No. 12.-We next took a similar disc, also 5 inches diameter, and by the same process compressed it into an ellipsoidal form, the longer axis of the base being 5 inches and the shorter 4 inches. The result was a perfect arch along the longitudinal section rising inch vertically. The length of the arch was 51 inches. The section along the short axis commenced with a concave curvature from the periphery towards the centre, which changed into a prominent convex curve as it approached the centre.1 An analysis of the movements proves that the material stretched along the long axis and was compressed along the short axis; probably an area of the apex of the dome was stretched in both directions. I have thought it unnecessary to reproduce this photo. TH CHAPTER XV FOLDING OF CLAY STRATA-PLATES BY THE Compressor.—With the object of applying circumferential compression to circular discs or plates of clay a 'compression band' was devised. This consisted of a thin pliable band of zinc, 2 inches wide, to which a strap of similar zinc 16 inch wide was riveted at one end to the 2-inch band, the other end being passed through an aperture or slit near the opposite end of the 2-inch band. A handle was fixed to the free end of the strap, and another to one end of the band. When these handles were drawn apart, in the direction shown by arrows on the photo, Plate XV., by means of a cramp-screw, a gradual tightening of the band took place and a reduction of the circumferential girth. The photograph of the actual machine (Plate XV.) will fully explain the extremely simple action of the band compressor,' which was made for me by my son, who also assisted to carry out the following experiments. The material used in the experiments was modelling clay. This was made very plastic and |