One fact interested Peter very much, and that was that usually the slats were thinnest where the wool was longest. "I suppose the strength of the sheep all went to its hair," speculated he to Nat. "Isn't it funny that it should!" Another thing the boys learned about sheepskins which was very different from the treatment of calfskins was that before the slats could be tanned they had to be put through a powerful press and have the grease squeezed out of them. "The skin of a sheep has a vast amount of oil in it," explained one of the workmen, "and it is impossible to do anything until this grease has been extracted; so we put a bunch of skins under a heavy press and then collect the grease that runs out, refine, and sell it." Peter and Nat watched this pressing with great interest. When the skins came out of the press they were so hard and stiff that it was necessary to put them into the revolving drums that separated and softened them. This was called "wheeling up the slats." The odor in the press room was far worse than anything that Peter had yet encountered--much more disagreeable than was an ordinary beamhouse. Both he and Nat were only too glad when noon time came and they could get out into the air. "Whew!" cried Peter, throwing himself down in the sunshine, "I hope they don't put us in that press room to work, Nat." "It's fierce, isn't it?" Nat answered. "The men must hate it." "I suppose they get accustomed to it just as I got used to the beamhouse," Peter said. "Why, when I began work in the beamhouse of Factory 1 I thought I never could endure it. Do you remember how you tried to cheer me up that first day?" Nat laughed at the memory. "Indeed I do. You looked perfectly hopeless, Peter." "That's about the way I felt," smiled Peter, "and I believe I'd feel so again if I thought I had weeks of that press room smell before me." But Peter need not have feared any such calamity, for after lunch he and Nat were given a lesson in tanning sheepskins and were told they were to work at that task until further notice. The process, they discovered, differed very radically from the calfskin treatment with which they were so familiar. Many of the slats were tanned by being laid in trays of fine, moist powder that looked like brown sugar. "What is this stuff?" inquired Peter of a man who stood near by. "That is sumac, young man." "Sumac! Just common sumac?" "Well, no. It is the same sort of thing, though. We import this from Sicily, because the foreign leaves grow larger and contain more tannin. Sicilian sumac makes better leather than does the American variety, which comes chiefly from Virginia." Peter nodded. "And how long, pray, do the skins lie covered up in this snuffy brown powder?" questioned Nat.