"I think that this thing is a sort of engineer's handbook," he said. "In the front there is a section devoted to mathematical tables. You know, a table of logs to the base twelve which is because the Martians had six fingers on each hand. There is what seems to be a table of definite integrals--at least if I were writing a handbook I'd place the table of integrals at the last part of the math section. The geometry and trig is absolutely recognizable because of the designs. So is the solid geom and the analyt for the same reason. The next section seems to be devoted to chemistry; the Martians used a hexagonal figure for a benzene ring, too, and so that's established. From that we find the key to the Periodic Chart of the Atoms which is run vertically instead of horizontally, but still unique. These guys were sharp, though; they seem to have hit upon the fact that isotopes are separate elements though so close in grouping to one another that they exhibit the same properties. Finding this will uncover a lot of mystery." "Yeah," agreed Baler, "from a book of this kind we can decipher most anything. The keying on a volume of physical constants is perfect and almost infinite in number. What do they use for Pi?" "Circle with a double dot inside." "And Planck's Constant?" "Haven't hit that one yet. But we will. But to get back to the meat of this thing, the third section deals with something strange. It seems to have a bearing on this gadget from the top of the tower. I'd say that the volume was a technical volume on the construction, maintenance, and repair of the tower and its functions--whatever they are." Barney spread the volume out for Jim to see. "That dingbat is some sort of electronic device. Or, perhaps subelectronic. Peel away that rusted side and we'll look inside." Jim peeled a six-inch section from the side of the big metal tube, and they inspected the insides. Barney looked thoughtful for a minute and then flipped the pages of the book until he came to a diagram. "Sure," he said exultantly, "this is she. Look, Jim, they draw a cathode like this, and the grids are made with a series of fine parallel lines. Different, but more like the real grid than our symbol of a zig-zag line. The plate is a round circle instead of a square, but that's so clearly defined that it comes out automatically. Here's your annular electrodes, and the ... call 'em deflection plates. I think we can hook this do-boodle up as soon as we get to our place in Lincoln Head." "Let's go then. Not only would I like to see this thing work, but I'd give anything to know what it's for!" "You run the crate," said Barney, "and I'll try to decipher this mess into voltages for the electrode-supply and so on. Then we'll be in shape to go ahead and hook her up." * * * * *