In cutting out the gores of the envelope it is possible to waste fully ⅓ of the material unless the work is skilfully planned. Taking the width of the chosen material as a basis, we must first deduct from ¾ of an inch to 1½ inches, in proportion to the size of the proposed balloon, for a broad seam and the overlapping necessary. Dividing the circumference at the largest diameter--the “equator” of the balloon--by the remaining width of the fabric gives the number of gores required. To obtain the breadth of each gore at the different “latitudes” (supposing the globe of the balloon to be divided by parallels similar to those of the earth) the following table is to be used; 0° representing the equator, and 90° the apex of the balloon. The breadth of the gore in inches at any latitude is the product of the decimal opposite that latitude in the table by the original width of the fabric in inches, thus allowing for seams. [Illustration: Finsterwalder’s method of cutting material for a spherical balloon, by which over one-fourth of the material, usually wasted in the common method, may be saved. It has the further advantage of saving more than half of the usual sewing. The balloon is considered as a spherical hexahedron (a six-surfaced figure similar to a cube, but with curved sides and edges). The circumference of the sphere divided by the width of the material gives the unit of measurement. The dimensions of the imagined hexahedron may then be determined from the calculated surface and the cutting proceed according to the illustration above, which shows five breadths to each of the six curved sides. The illustration shows the seams of the balloon made after the Finsterwalder method, when looking down upon it from above.] TABLE FOR CALCULATING SHAPE OF GORES FOR SPHERICAL BALLOONS 0° 1.000 3° 0.998 6° 0.994 9° 0.988 12° 0.978 15° 0.966 18° 0.951 21° 0.934 24° 0.913 27° 0.891 30° 0.866 33° 0.839 36° 0.809 39° 0.777 42° 0.743 45° 0.707 48° 0.669 51° 0.629 54° 0.588 57° 0.544 60° 0.500 63° 0.454 66° 0.407 69° 0.358 72° 0.309 75° 0.259 78° 0.208 81° 0.156 84° 0.104 87° 0.052⅓ In practice, the shape of the gore is calculated by the above table, and plotted out on a heavy pasteboard, generally in two sections for convenience in handling. The board is cut to the plotted shape and used as the pattern for every gore. In large establishments all the gores are cut at once by a machine. The raw edges are hemmed, and folded into one another to give a flat seam, and are then sewn together “through and through,” in twos and threes: afterward these sections are sewn together. Puckering must be scrupulously avoided. In the case of rubberized material, the thread holes should be smeared with rubber solution, and narrow strips of the fabric cemented over the seams with the same substance.