CHAPTER I. Introduction (Part 4)

which thej possessed millions of years ago before their imprisonment in the lime. You can extinguish the flame of a taper by plunging it in this gas, or you can pour the gas over a flame, as one pours water, with the same effect it would have produced millions of years ago. The experiment is an interesting one, and can be tried without difficulty. The importance to plumbers of an elementary knowledge of these subjects will become more apparent to each artisan in proportion as he obtains more of that information. Plumbers often meet this dangerous gas when fixing or repairing pumps in deep closed-in wells. Its presence is detected by lowering a lighted candle into the well, when the flame will be extinguished, as the man's life would be under similar circumstances. The universal force of gravity is one of the physical phenomena of nature which intimately concern the plumber in his business, and he will be wise to endeavour to com- prehend something about it. Gravity is that mysterious omnipresent power by which every particle of matter attracts every other particle. By the force and effect of gravity, under the heat of the sun, the vapour and the clouds are caused to ascend, the rain and the dew to fall. It causes the upward springing of the fountain into the air, as well as the flow of rivers downwards to the sea ; it causes water to flow through pipes, and sewage to discharge through drains ; it causes water to rest in our cisterns and to flow out from them ; it enables us to ventilate and heat our buildings, and it produces the circulation of hot water in pipes; it governs and controls every action of our bodies and every detail of our craft. No particle of matter, solid, liquid, or gaseous, invisible though it may be to our eyes, is too minute to be free from this universal force of gravity. 32 DOMESTIC SANITARY DRAINAGE AND PLUMBING. sometimes called weight. The word " weight " conveys the idea of the downward attraction towards the centre of the earth alone. Gravity is more than that; it is a universal force of attraction, innate in and belonging to every particle of matter, whereby every atom must of necessity attract every other atom. If you place two blocks of stone on a bench, one large and one small, they are drawn downwards and held from flying together by the overpowering force of gravity exerted on them by the enormous mass of matter in the earth ; but these two blocks have a mutual attraction for each other, so that, if all other attraction could be destroyed, they would instantly fly together — the large block would draw the small block towards it and the small block would draw the large block towards it, each moving a certain distance at a certain speed in exact proportion to their relative mass. If they were blocks of equal mass each would move an equal distance at an equal speed and meet exactly half-way. Plumbers, as practical men, should seek to realise this universal attraction. The sun attracts the earth, and the earth attracts the sun. The earth attracts the moon, and the moon attracts the earth, each in proportion to its mass and to its distance apart from the other. The ebb and flow of the tides are chiefly caused by this attraction of the sun and moon. The waters, being drawn up from the earth towards the sun and moon, tend to follow these bodies, producing the tides. This force of gravity has been accurately measured. All bodies, though differing in volume and mass, such as lead and water, fall in a vacuum at an equally increasing velocity, and it has been ascertained that at the end of one second of time in falling the velocity acquired is 321948 feet, or 322 feet nearly in one second, and this is taken as the measure of the force of gravity. It is important ELEMENTARY SCIENCE FOR PLUMBERS. 33 that every plumber shonld know and remember that all hydraulic calculations are based upon that unit of measure- ment which is algebraically called g. The flow of water through pipes and drains, and along open channels, and from cistems and reservoirs is solely caused by this force of gravity acting on each atom of the water, directly tending to draw all towards the centre of the earth, a tendency which \a checked by the bed, or channel, or vessel by which the water is carried or supported. A knowledge of the laws of gravitation means, to the hydraulic engineer, a knowledge of the foundation on which his practice rests. To the philosophers Galileo and Newton we are indebted for this knowledge. We here find the highest discoveries of science serving for the daily practical guidance of engineers and artisans. One law of gravitation determines that all bodies on the earth, whatever may be their volume and mass — lead, water, etc. — fall freely in vacuo, with equally increasing velocities, over the space of 161 feet in one second, 644 feet in two seconds, 1449 feet in three seconds, 2576 feet in four seconds. We find these distances easily by squaring the number of seconds during which the body is falling, and multiplying the rest by 161. For one second „ two seconds „ three ,, „ four ,. ,. eight „ !>=: 1x1=1x16'!=: 16 '1 feet in one second. 2^=2x2= 4x161= 644 ,, two seconds. 8« = 8x3= 9x161= 144-9 ,, three „ 4«=4x 4 = 16x16-1= 2576 .. four 8«=8x 8 = 64x161 =10304 „ eight ,, Galileo discovered the law that the space described by bodies falling freely under the action of gravity is propor- tional to the square of the time elapsed from the beginning of the fall. The top of the flagstaff on the Eifiel Tower in Paris is D 34 DOMESTIC SANITARY DRAINAGE AND PLUMBING. about 1,030 feet high ; we find that a bullet dropped from this height will reach the ground in eight seconds, and will have attained a velocity of 2575 feet per second at the end of the eighth second. To find the space fallen through in any given time multiply the square of the number of seconds by 161, which is the distance fallen through in feet during the first second of falling — 82 = 8x8 = 64x161 = 1 ,0304 feet in eight seconds. The velocity increases second after second in falling in a steady ratio. To find the velocity in feet per second acquired in falling, for any number of seconds, at the end of the final second, multiply the number of seconds by 322 — 8 X 322 = 2575 feet velocity per second at end of eighth second ; or multiply the distance fallen through in feet by 644, and take the square root of the product — 1,030x644 = 66,332; ^66,332 = 2575 nearly = velocity in feet at end of eighth second ; or multiply the square root of the space fallen through in feet by the square root of 644, the result will be the same — Vi;;030 feet = 32-1 nearly; ^64-4 = 8025 x 321 = 2575 nearly = the velocity acquired in feet per second at the end of the eighth second of falling. A bullet dropped from the dome of St. Paul's, London, will fall the 272 feet in 43 seconds. In every case a fraction of time must be allowed in addition, for the resistance of the air medium acting on the falling body. The depth of very deep wells may be approximately measured in a similar fashion, allowing extra time for the sound of the bullet or stone, on striking the water, to travel up to the ear. ELEMENTARY SCIENCE FOR PLUMBERS. 35 In calculations for plumbing and hydraulic work frac- tions are frequently neglected for convenience, but then care should be used to insure that the actual results shall be more, rather than less, favourable than the calculated results in consequence. Accuracy is always an advantage, and should be cultivated in all calculations. In the case of a falling body the velocity is rapidly in- creased if no resistance or friction affects it, as in vacuo ; in the case of an ascending body the velocity is diminished in the same ratio. In order to throw a column of water 16 feet high it must be given an initial velocity of 322 feet per second to overcome the attraction of gravity, together with an additional velocity to overcome the resistance or friction of the air. To obtain any given velocity in water flowing through pipes and drains the pipes must be given not only the fall required by the laws of gravity to produce that velocity, but also an additional fall or head to overcome resistance or friction offered by the surface over which the water flows and by the air through which it passes. If we could obtain a vertical glass tube 16 feet high and, by extracting the air, form a perfect vacuum within the tube, and if we could, without admitting air, let fall a leaden shot and a drop of oil, they would each, as before explained, fall in one second, and would each have attained a velocity of 322 feet per second at the end of the second of time occupied in falling. Let fall some water in the same tube ; it will drop in the same space of time, and remain in a mass unbroken, producing a dry click, like a solid, on striking the bottom. Such a tube forms what is called a '' water hammer.'' Smoke also falls in vacuo, for smoke has weight, and all gases have weight. 36 DOMESTIC SANITARY DRAINAGE AND PLUMBING. The specific gravity of various solids, liquids, and gases intimately concerns plumbers. Every solid, every liquid, and every gas possesses a density specific or peculiar to itself, and different relatively to all other substances. This is known as its specific gravity. It is found in three ways, either by the hydro- static balance, the hydrometer, or the specific gravity fiask. The specific gravity of each solid and liquid is ascertained and determined generally by careful comparison with an equal bulk of pure distilled water at the temperature of 39" F. or 4° C, the temperature at which water attains its greatest density, before it expands in freezing. In our country the weight of a cubic inch of water at 60' F., with atmospheric pressure at 30 inches of mercury, is taken as the standard. It weighs 252'458 grains. There are 7,000 grains in 1 lb. avoirdupois; 70,000 grains in a gallon; 277272 cubic inches in a gallon. The specific gravity of gases is ascertained by comparison with dry atmospheric air at 60' F. and 30 inches barometric pressure as the standard Liquids and gases of greater specific gravity will sink below liquids and gases of less specific gravity. Thus water will sink below oil in a mixture; molten lead will sink below molten tin in plumber's solder ; molten lead and tin will sink below molten zinc; carbonic acid gas will sink below atmospheric air. By acquaintance with the specific gravity of his materials, etc., the plumber knows what results he shall find in any combinations. He knows that while using his solder he must keep it stirred, else the tin must rise to the top, because the lead, owing to its greater specific gravity, will sink to the bottom ; he knows that if accident or mischief brings zinc into his solder he can purify the solder by ELEMENTARY SCIENCE FOR PLUMBERS. 37 melting, until the zinc is driven to the surface, where it can be skimmed off. The practical plumber, of course, is aware of these facts ; but science explains to him the reason and the cause of them. The plumber knows that on going down into a well to fix a pump he may find a layer of dangerous carbonic acid gas lying at the bottom, because the specific gravity of that gas is greater than that of air, and thus he is specially warned of a danger to his life, and can take due precaution in time. Some men will say, " We all know of that danger with- out science to teach us "; but it is certain that the practical man who knows something, by scientific study, of the specific nature and deadly effects of carbonic acid gas, will realise more thoroughly the danger, will remember about it more cer- tainly at the proper time, and will know better what measures to take, under various circumstances, to secure safety for his own life and for the lives of his fellow-workmen. Mercury is thirteen and a half times and lead eleven times denser than water; lead is thirty times denser than poplar wood ; the specific gravity of mercury is thirteen and a half times greater than the specific gravity of water, and that of lead is thirty times greater than that of poplar wood. Place two small glass vessels one in each pan of a scales equally balanced; fill one with water, and pour mercury into the other until the balance is again attained. Find a small vessel which this quantity of mercury will exactly fill, and the quantity of water in the opposite pan of the balance will exactly fill the same vessel thi'rteen times and a half. So also one cubic inch of lead placed in the scale will require to have thirty cubic inches of poplar wood in the opposite scale of the balance to secure equilibrium. Plumbers will find a table of the specific gravity of a few solids, liquids, and gases serviceable for reference from ^8 DOMESTIC SANlTAkV DRAINAGE AND PLUMBING. time to time; it is unnecessary to overload the memory with figures, but it is an advantage to have them at hand and available. Solids. Iridium . 28-00 Sandstone 2-60 Platinum, cast 20-86 Porcelain 2-24 „ hammered 22-06 Rock Salt 1-92 Gold, cast . 19-26 Ice at 32" F. . 0-926 heaA, cast 11-86 Ivory 1-92 Silver, cast . 10-47 Chalk 2-65 Bismuth 9-82 Sulphur 2 08 Copper, cast . 8-85 Coal 1-3 Copper wire . 8-95 Phosphorus 1-77 Brass 8-39 Amber 108 Nickel 8-88 Wax 0-97 Steel 7-82 Sodium 0-97 Iron, hammered 7-79 Ebony 1-19 „ cast . 7 24 Oak 0-91 Tin 7-29 Mahogany 1-06 Zinc 6-862 Box 1-32 Antimony . 6-71 Beech 0'86 Arsenic 5-959 Ash 0-84 Iodine 4-94 Maple 0-76 Mica 2-93 Walnut 0-68 Sugar 1-6 Pitch pine 0-66 Diamond 8-63 Yellow pine . 0-65 Crown glass . 2-76 Elm 0-60 Flint glass 878 Cedar 0-59 Plate glass . 2-37 Larch 0-64 Aluminium . 2-67 Poplar 0-38 Marble 265 Cork 0-24 Granite . 2-76 Elder pith 0-08 Liquids AT 32° F. Mercury 13-596 Linseed oil . . . 0940 Sulphuric acid 1-86 Spirits of wine 0-835 Nitric acid . 1-52 Proof spirit . 0-920 Phosphoric acid 1-55 Boi-deaux wine 0-994 Hydrochloric acid . 1-218 Burgundy wine 0-991 Mui'iatic acid 1-200 Olive oil 0-915 Milk 1-03 Ether, hydrochloric 0-874 Sea water 1-026 Turpentine 0865 Vinegar 1-026 Brandy 0-837 Tar 1-015 Human blood . 1-053 Water at 39" F. 1-000 Alcohol . 0-796 Water at 32' F. 0-9998 Ether, sulphur ic 0-720 ELEMENTARY SCIENCE FOR PLUMBERS. 39 Gases and Vapoubs Coup arid with Air at same Temperature AND Pressure. Oxygen . .1108 Carbonic acid gas . 1-529 Nitrogen 0-972 Siilphurons acid gas . 2-247 Hydrogen 0-069 Sulphuric acid gas . 2 768 Bromine 5-395 Marsh gas . 0-569 Chlorine 2-470 Olefiant gas . . 0-978 Steam 0-622 Coal gas . 0-500 Ammonia 0-596 Air . 1-000 Iodine 8-701 Gases Compared with Water at 39** F. Oxygen . 0001432 Hydrochloric acid gas 0-00164 Atmospheric air . 0-001298 Nitrous oxide 000197 Nitrogen . 0-001267 Carbonic acid gas . 000198 Hydrogen 0-0000894 Water at 39'* F. . . 1000 Chlorine . , , 0-008209 Cohesion, or the attraction of cohesion, is that energy or force which we see displayed around us, uniting and holding together, with various d^rees of effective power, the different particles of every solid and liquid substance. We see phenomena the most curious daily passing before our eyes, and hardly consider them worthy of notice, yet they form some of the scientific questions most difficult of explanation and solution. If a piece of ice be thrown into the air all its particles are held together by the attraction of cohesion, and all participate in the motion equally. If we grind the ice to fine powder and pour the powder down a sloping board the particles will flow over each other, resembling in appearance the flow of water; or if we place the powder in a vessel with a hole in the bottom the powder will flow out through the hole in appearance like water, but each small grain in the powder is a true solid, the particles being held together by cohesion. Although in grinding the solid to powder we have annulled the cohesion between many particles, we have not succeeded in annulling it in all. But when we apply another power of nature, that of heat, to the ice in solid or in powder. 40 DOMESTIC SANITARY DRAINAGE AND PLUMBING. we find that all the particles are torn asunder, and have their cohesion so greatly reduced that they will slide about and roll over one another and mingle every way under a very slight force indeed; yet, although the attraction of cohesion seems to have changed its character in water, it still exists, holding the particles in close contact, unless some other greater force overcomes it, as when water is forced into a spray sometimes like fine dust by the resistance of the air upon its particles when in motion. If this water be driven into steam