"I do," said Jim: "you have been and spattered yourself with silver, and the sunlight has turned it black. You are in a nice fix, for nothing will take it off." "The coat was only a work jacket," said Fred, "and I don't care a bit about my hands. But let us see what you have bought." "In the first place," said Jim, opening his packages, "here are some tin plates--great big fellows, too, and all for fifty cents. And here is some collodion. These green crystals are sulphate of iron, and the man says we must keep them in a very tight bottle, because if the air gets at them they will spoil. He told me they were made of old nails and sulphuric acid. Do you believe it? These green crystals we must dissolve in water before using. This stuff in the bottle is acetic acid. Doesn't it smell queer? And here is some hyposulphite of soda; and that's all. Now let's get to work." The two hours were now over, and Fred returned to his silver bath, and let it run through a filter, when, by rule, the bath was ready. It was placed in a flask, and tightly corked. "Now, Jim," said Fred. "I guess we would better leave everything until Saturday, because to-morrow we have an examination in algebra, and ought to cram for that to-night; and to-morrow afternoon is the ball match, and in the evening we shall be tired." At last Saturday morning came, bright and sunny, and the two boys began in earnest the task of taking a picture. Fred had procured a tall narrow glass vessel to hold the silver bath, and a glass dipper with which to suspend the plate, and having mixed the developing and fixing solutions, the boys were at last ready. "Now you pour on the collodion," said Jim, "and put the plate in the bath, while I get the camera in position and adjust the focus." "What are you going to take?" asked Fred. "I guess I'll try old Spriggins's back yard," answered the other. "He's got a big grape-vine arbor there that will take immense." Fred, left to himself, poured the collodion over the plate, and gently tilted it from side to side. The liquid did not flow evenly, but lay in rings and streaks all over the surface. "Why didn't we try the Professor's gum-arabic, and save collodion!" he exclaimed. But not discouraged by failure, he tried again, and by sheer luck succeeded in making a smooth surface. In about five seconds he put the plate in the bath, and awaited the result. When he removed it, instead of being finely coated with silver, the plate appeared cracked, greasy, and spotted. "Oh, misery!" he cried, "the bath is all full of yellow stuff. What shall I do?" Hearing this, Jim returned to the laboratory, and with his usual calmness simply said, "Filter." Fred did so, and in a few moments a clear bath was again obtained. "How did that happen, I wonder?" said Fred. "I don't believe you allowed the collodion time enough to set," was the answer. "Let me try this time."