"Go ahead;" said Mr. Techman. "To tell you the truth, I've never given the philosophy of it two thoughts, and nobody ever taught me." "Oh! In that case," said the neighbor, "perhaps The point is not to waste your I can tell you a little. heat up the chimney. Get the box of the furnace full of live coal, but don't let it get any hotter than the weather calls for. Be sure nevertheless to keep the draught in the front above the fire closed all the time." Here Mr. Techman broke in with "Why, how can you keep it from running away? That draught is the one that checks the fire." "Now I know where your money goes," said the neighbor. "When that draught is open, the air draws right through over the coal and carries off the hot gases right up the chimney instead of letting them remain above the coal to heat the walls of the furnace which in turn warm the air that is going to come up through the radiators to the rooms. The secret is to open the draught of the smoke pipe, and keep the front door draughts closed both top and bottom. Then the escape of heat up the chimney will be checked, and the coal will smolder a long while, keeping the furnace walls hot so as to warm the air that flows to the radiators. When the house gets too cool, shake the fire to get rid of the ashes. The coal being then not very hot, there will be hardly any clinkers formed, and the fire will be cleaned. Then throw on fresh coal, close the draught in the smoke pipe, and open the lower draught. Soon the fire will be hot again. Then close up the lower draught, open the smoke pipe draught, and so on." Mr. Techman thanked his neighbor not only for loaning the six hods of coal which he returned in a few days, but for his good advice which would last him many years. This he immediately put in practice with almost magical results. The house kept warm. The fire kept clean. Clinkers formed so little that he could keep a fire many weeks without dumping, and very little good coal went into the ash barrel. What was not so plain at the time, but showed soon enough, in money saved if not to the eye, was that the coal no longer flew away up the chimney. It was about February that they had their talk, and Mr. Techman finished the winter with only two tons of coal. The next year he cut his usual coal pile in half and kept the house warmer than it had ever been before. When he reflected on how foolishly he had allowed hundreds of dollars of his good money to fly away up chimney for lack of applying the principles of his education, Mr. Techman could not be very proud of himself. It reminded him of the only examination he had ever flunked at college, when he had ground up all night out of the text book, and been completely dazed, and all his classmates with him, by a set of problems on practical applications of higher mathematics which followed directly out of the principles of the book but were not treated specifically in it. What are brains and knowledge for but to apply? CHAPTER XII RAGS AND VELVET GOWNS Hark! hark! the dogs do bark, How many strands are there in a silk thread? Count them. Take the thread and untwist it till the fibres can be unraveled and separated. Pull out a piece containing one single filament and see how fine it is. Such single silk fibres used to be used for supporting the delicate moving parts of scientific instruments, and for making the crossed threads in telescopes. But now it is commoner to use fibres of quartz crystal. One can hardly believe, as he looks at a rock crystal, far harder than glass, that it would be possible to make threads of it as fine, yes, very much finer than a single fibre of silk, but it can be done very easily. The first process for making quartz fibres was invented by Mr. C. V. Boys of England and it was very neat. A little bow and arrow was used. A bit of crystal was attached to the bow and another to the arrow. They were then melted together in a fine hot oxyhydrogen flame. At the right instant the arrow was shot away and trailed after itself a fine thread of quartz less than a ten-thousandth of an inch in diameter. Molasses candy or glue can be drawn out into fine threads much in the same way. This, indeed, except for the bow and arrow, is what a spider or a silkworm does, or any caterpillar that spins a cocoon of threads. These creatures have a store of liquid something like mucilage, from which they can draw out their almost never-ending thread to build into a web or cocoon. As much as a half mile of fibre can be reeled from a single silkworm's cocoon. The silk industry was first practised commercially in China. The Chinese guarded the secret of the silkworm very carefully. They kept it from going outside of China, it is said, for over 2,500 years. Silk culture gradually spread through Korea to Japan and westward to India about the year A. D. 300. Later, the Emperor Justinian at Constantinople induced two Persian monks who had lived in China and learned all about the silk industry to impart their knowledge. These monks traveled back to China under his patronage and returned to Constantinople about the year A. D. 550, bringing silkworm eggs concealed in a bamboo cane. All the silkworms in Europe descended from this first stock. From Constantinople the silk industry gradually spread westward, and it was established in France about the time of Columbus. The silkworm feeds with an enormous appetite on the leaves of the mulberry tree and spins a cocoon about as big as the little finger. This shell is a perfect network of the tiny fibres imbedded together in a sticky mass which dries firmly. In order to reel off the silk fibres, the cocoons must be softened in hot water nearly of boiling temperature. The reeling is quite a skilled art and is done by the aid of a special machine which draws the silk off from the cocoons as they bob about in a tub of warm water. A number of cocoons are reeled at once to form a single thread of from five to twenty strands, the "raw silk" of commerce. This long thread of many strands is still too weak and a number of such threads are twisted and these again recombined and twisted to make the ordinary thread used in weaving. But still its separate fibres are covered by the gummy matter that made the cocoon firm and hard. It has no lustre or smoothness, and feels stiff and harsh. To remove the gum, the silk is treated with strong hot soapy water nearly at boiling, and again with a weaker cooler soapy solution. The two processes take several hours and dissolve away nearly a quarter of the weight of the raw silk. After careful washing and drying, the silk now takes on its shiny lustrous soft texture. In the dyeing of silk, chemical compounds of tin are used as fixing agents technically called "mordants." They have the property of soaking into the fibres, where they make insoluble compounds with the dyes used to give the desired colors. Thus the colors are "fast" and are not lost by washing the goods in water. The silk industry of France and Italy, and even of the whole world, was endangered about the year 1860 |