Then there was what the boys called a circular saw, made of a flat, circular piece of lead, as large as the top of a tea cup. Jonas had hammered it out of a bullet. There were saw-teeth cut all around the circumference, and two holes bored through the lead, at a little distance from the centre, one on each side. There was a string passed through these holes, and then the ends were tied together; and to put the circular saw in motion, this string was held over the two hands, as the string is held when you first begin to play cat's-cradle. Then, by a peculiar motion, this saw could be made to whirl very swiftly, by pulling the two hands apart, and then letting them come together again,--the string twisting and untwisting alternately, all the time. There were various other articles of apparatus for performing philosophical experiments; such as a prism, a magnet, pipes for blowing soap bubbles, a syringe, or squirt-gun, as the boys called it, made of a reed, which may be said to be a philosophical instrument. Jonas made a collection of specimens of _wood_, which was, on the whole, very curious, as well as somewhat useful. As he was at work sawing wood from day to day, he laid aside small specimens of the different kinds; as oak, maple, beech, ash, fir, cedar, &c. He generally chose small, round pieces, about as large round as a boy's arm, and sawed off a short piece about three inches long. This he split into quarters, and reserved one quarter for his specimen, throwing the others away. This quarter had, of course, three sides; one was covered with bark, and the other two were the split sides. As fast as Jonas got these specimens split out in this manner, he put them in the barn, upon a shelf, near the bench; and then, one day, he took them one by one, and planed one of the split sides of each, and then smoothed it perfectly with sand paper. Rollo, who was standing by at the time, asked him why he did not plane them all around. "O, because," said Jonas, "they are for specimens, and so we want them to show the bark on one side, and the wood on the other side, in its natural state; and the third side is enough to show its appearance when it is manufactured." "Manufactured!" said Rollo. "Yes," said Jonas; "planed and varnished, as it is when it is made into furniture." "Are you going to varnish the sides that you plane?" Jonas said he was; and he did so. He planed one side, and one end. He varnished the planed side, and pasted a neat little label on the planed end. On the label he wrote the name of the wood, and some very brief account of its qualities and uses, when he knew what they were. For instance, on the end of the specimen of walnut, was written in a very close but plain hand-- Walnut, very tough and hard. Used for handles.