LESSON XIX. Spell and Define. 2. Phosphor-us, a combustible sub- 21. Cer'tain, particular. stance. 25. Pro-jects', juts out. 2. Sulphur, a yellow mineral substance. 27. Sep'a-rate, to disjoin. 2. Al'co-hol, highly rectified spirit. room. 5. Nec'es-sa-ry, requisite, needful. 17. Ac-cu'mu-late, to collect. 27. Con'tact, union. 30. Slant'ing, oblique. 32. Un-der-stand', to comprehend. ERRORS.-2, Phos-pho'rus for phosphor-us; 2. al'ca-hol for al'co-hol; 6. bile'. ing for boil'ing; 10. hand'i-rons for and'i-rons; 15. beau'ti-fly for beau'ti-ful-ly, 25. teube for tube; 31. kep for kept; 37. cu'ris for curi-ous. PHILOSOPHY OF LAMP-LIGHTING,-CONCLUDED. J. S. C. ABBOTT. 1. ROLLO's father then repeated to her what he had just been telling Rollo, namely, that different substances take fire at different degrees of heat; and he said that it would be a very interesting experiment to take a long iron bar, and put a small quantity of several different substances upon it, in a row, and then heat the bar gradually from end to end, all alike, until it was very hot, and so see in what order the various substances would take fire. b 2. "I would have," said he, " phosphorus," sulphur, sawdust, charcoal, saltpeter, oil,- we should have to make a little hollow in the iron for the oil, alcohol, spirit of turpentine, and perhaps other things. The phosphorus would take fire first, I suppose, and then perhaps the sulphur, and others in succession." NOTES. -a Phosphorus is obtained from the bones of animals, by a chemical process. b Sulphur is found in the vicinity of volcanoes, where it rises to the surface of the earth. e Saltpe'ter is found ready formed in the East Indies, Spain, and the limestone caves of our own country; it is also made artificially. d Alcohol is obtained by the distillation of spirituous liquor. 3. "Well, father," said Rollo, "I wish you would. I should like to see the experiment, very much." 4. "No," said his father; I cannot actually try such an experiment as that. I could not get such a bar very conveniently; and if I had the bar, and all the substances, it could not be done very well, except in a chemical laboratory. But it would be a very pretty experiment, if it could be performed." 5. "Is there a very great difference," said Rollo's mother, "in the degree of heat necessary to set fire to these different things?" 6. "Yes," said Mr. Holiday; "I believe the difference is very great. Phosphorus inflames below the heat of boiling water, but it takes almost a red heat to set wood on fire. And iron will not take fire till it is white hot." 7. "Iron?" said Rollo, with surprise. 8. "Yes," said his father, "iron will take fire and burn as well as wood, if you heat it hot enough." 9. "I never knew that," said Rollo. 10. "The ends of the tongs and of the andirons do not burn," said his father, "simply because the fire is never hot enough to set such a large piece of iron on fire. 11. "But if we heat the end of a bar of iron very hot indeed, in a furnace, it will take fire and burn; and so if we take a very minute piece of iron, as big as the point of a pin, a common fire would be sufficient to heat that hot enough to set it on fire." 12. "Well, father," said Rollo, "let us try it." 13. "If we had some iron filings, we might sprinkle them in the fire, or even in the flame of a lamp, and they would burn." 14. 16 I wish I had some filings," said Rollo. 15. "Yes," said his father; "they burn beautifully." 16. "How can I get some?" asked Rollo. 17. “You can get some at a blacksmith's shop,' said his father. "The filings commonly accumulate behind the vice, and you can get plenty of them there. The next time you go by a blacksmith's shop, you had better go in and ask him to give you some." 18. "Well," said Rollo, "so I will." 19. "And now do you understand," said his father, " why it is that you can light a lamp more easily, when there is a little spirit of turpentine on the wick?" 20. "Yes, sir," said Rollo. "The spirit of turpentine need not get so hot before it takes fire, and so you do not have to hold the lamp-lighter so long, and burn your fingers." 21. "Will oil always take fire when it gets to a certain degree of heat?" asked Rollo's mother. 22. " Yes," said his father, "I suppose so." 23. "And yet," said she, "the lamp seems to take fire much more easily at some times than at others." 66 24. "Yes," said Mr. Holiday, that is true. If the wick is cut square across, and rises up only a very little way above the tube, it is very difficult to light it; because the tube itself and the oil below, keep the upper end of the wick cool. "And 25. "It is very hard to heat it, in that case, hot enough to set it on fire. But if the wick projects considerably out of the tube, then it is out of the way of the cooling influence of the metal, and you can heat the upper end more easily.” 26. "I never thought of that," said Rollo. 27. "That is the operation of it," said his father. if you push the wick open a little, so as to separate some of the fibers of it from the rest, then it will take fire more easily still; because the small part which is separated is more easily heated up to the necessary point, than it was when it was closely in contact with the rest, and so kept cool by it. 28. "That is the reason why a thin shaving takes fire so much more easily, than the outside of a large piece of wood. The outside of a large piece is kept cool by the parts of the wood behind it which touch it, while the shaving is heated through very soon." 29. "I did not know that before," said Rollo. 30. "In the cities," continued his father, "the lamp-lighters that trim and light the street lamps always cut the wick off, when they trim the lamps, in a slanting direction, so as to leave a point of the wick projecting up on one side. 31. "This point will light very easily; for it stands by itself, somewhat apart from the rest, and so is not kept cool by the rest of the wick. Then, when they put it into their great blazing torch, it heats this point to the degree necessary to influence the oil very easily. 32. "There is one thing more I want to tell you, and that will be all I have to say about lamps to-night; and that is, to explain to you the philosophy of putting them out. You must understand that two things are necessary to carry on combustion or burning. 33. "First, there must be air; and secondly, the body burning must be kept above a certain degree of heat. Now, if you either suddenly shut off the air from the substance that is burning, or suddenly cool the substance, it will go out. For instance, the wick,-you have to heat it to a certain degree before it will take fire. 34. "Now, if after it is burning, you suddenly cool it below that degree, it will go out; or if you shut out the air from it, then it will go out; for it cannot burn unless it continues hot, and unless it continues to have a supply of air. 35. "Now, when we blow out a lamp, we stop the burning by cooling it. The cool air which we blow against it suddenly cools the upper end of the wick below the point of combustion, and so it goes out. On the other hand, when we put it out by an extinguisher, we stop the burning by means of shutting out the air. Either mode will stop the combustion." 36. "And how is it when we put on water?" asked Rollo's mother. a NOTE. The reason why water extinguishes flame appears to be, first, because it is always cooler than the burning body, since it cannot be heated above 212 degrees, and therefore would extinguish it by cooling; and secondly, because two bodies cannot occupy the same space at the same time, and therefore the water excludes the air which is the supporter of combustion, and that extinguishes the flame by removing the cause of it. 37. "Why, that is somewhat different from either," said Mr. Holiday; "or rather it is both combined. There is something very curious in the operation of water upon fire; that I will explain at some other time." QUESTIONS. 2. How is phosphorus obtained? 2. Where is sulphur found? 2. Where is saltpeter found? 2. How is alcohol obtained? 6. At what temperature do phosphorus, wood, and iron, inflame? 13. What takes place when iron filings are sprinkled in the fire? 24. Why is it difficult to light a lamp, when the wick is cut short and square across? 30. How do city lamp-lighters always cut off the wicks of their lamps? 33. What two things are necessary to carry on combustion? 35. How is a lamp extinguished by blowing it out? 35. How by an extin guisher? 36. How is a lamp or flame extinguished when we put on water? ERRORS.-2. Wins for winds; 3. weel for wheel; 3. wite for white; 3. blas for blasts; 4. cheuse for choose; 4. hurth for hearth. THE SKATER'S SONG. 1. AWAY! away! E. PEABODY. our fires stream bright Along the frozen river, And their arrowy sparkles of brilliant light |