In the manufacture of shoes the finest quality of rubber is received in wooden boxes 4 × 2 × 1½ feet, containing about 350 pounds in lumps of 1 to 75 pounds. These lumps are cut to suitable size, and are then ground and washed in the machine shown in Fig. 161, water and steam being sprayed on the rubber during the operation. It is then worked into sheets or mats between rolls. From the grinding room the sheets are taken to the mixing room, where lampblack, sulphur and other ingredients are added, and worked into it by being passed many times between heated rolls, the sheets being finally reduced to a thickness of less than 1/32 of an inch. The rubber sheets are then applied to a cloth backing by cloth calendering rolls, shown in Fig. 162, which are steam heated and by great pressure serve to incorporate the sheets of rubber and cloth into intimate and inseparable union. Out of this rubber fabric, which is made of different thicknesses for the upper, sole and heel, the patterns for the shoe are cut, and the parts are deftly fitted around the forms by girls, and secured by rubber cement, as shown in Fig. 163. The shoes are then covered with a coat of rubber varnish, and are put into cars and run into the vulcanizing ovens, where they remain from six to seven hours at a temperature of about 275°. The goods are then taken out, and after being inspected are boxed for the market. The vulcanizing is a very important part of the manufacture of a rubber shoe, for it is absolutely necessary in order to give them stability and wearing qualities. A shoe that had not been vulcanized would mash down, spread, become sticky and go to pieces after a few hours’ wear. The rubber shoe industry of the United States is carried on by about fifteen large companies, representing an investment of many millions of dollars, most of which companies are located in Massachusetts, Rhode Island and Connecticut. Some idea of the immensity of this industry may be obtained from the import statistics. In 1899 the United States alone imported crude rubber to the extent of 51,063,066 pounds, as much as 1,000,000 pounds a month coming from the single port of Para. The export of manufactured rubber goods for the same year amounted to $1,765,385. The statistics for Great Britain for 1896 showed the imports of rubber to that country to be one-third more than the imports of the United States. Germany also is a large consumer. The great Harburg-Vienna factories cover sixty-seven acres, are capitalized at 9,000,000 marks, and employ 3,500 hands. Much fine technical apparatus, toys, and balls are made here, the daily output of balls reaching 8,000. These, with the Noah’s arks of India rubber animals, are the delight of the little ones all over the world.