Practical Mechanics for Boys Part 19

24 Grains (gr.) make 1 Pennyweight (pwt.) 20 Pennyweights make 1 Ounce (oz.) 12 Ounces make 1 Pound (pd.)

APOTHECARIES WEIGHT.

For Drugs, Medicals and Chemicals.

20 Grains (gr.) make 1 Scruple (sc.) 3 Scruples make 1 Dram (dr.) 8 Drams make 1 Ounce (oz.) 12 Ounces make 1 Pound (pd.)

LINEAR MEASURE.

For Surveyors' Use.

12 Inches make 1 Foot 3 Feet make 1 Yard 5-1/2 Yards make 1 Rod 40 Rods make 1 Furlong 8 Furlongs 1 Mile

LONG MEASURE.

12 Inches make 1 Foot 3 Feet make 1 Yard 6 Feet make 1 Fathom 5-1/2 Yards make 1 Rod or pole 40 Poles make 1 Furlong 8 Furlongs make 1 Mile 3 Miles make 1 League 69-1/2 Miles make 1 Degree

SQUARE MEASURE.

144 square inches make 1 square foot 9 square feet make 1 square yard 30-1/2 square yards make 1 square pole 40 square poles make 1 square rod 4 square rods make 1 acre 640 square acres make 1 acre mile

SOLID OR CUBIC MEASURE.

1,728 Cubic inches make 1 Cubic foot 27 Cubic feet make 1 Cubic yard 128 Cubic feet make 1 Cord of wood 24-3/4 Cubic feet make 1 Perch of stone

DRY MEASURE.

2 Pints make 1 Quart (qt.) 8 Quarts make 1 peck (pk.) 4 Pecks make 1 Bushel (bu.) 36 Bushels make 1 Chaldron (ch.)

LIQUID MEASURE.

4 Gills (g.) make 1 Pint (pt.) 2 Pints make 1 Quart (qt.) 4 Quarts make 1 Gallon (gal.) 31-1/2 Gallons make 1 Barrel (bbl.) 2 Bbls., or 63 gals., make. 1 Hogshead (hhd.)

PAPER MEASURE.

24 Sheets (sh.) make 1 Quire (qu.) 20 Quires make 1 Ream (r.) 10 Reams make 1 Bale (ba.) or bundle.

TABLE OF TEMPERATURES.

Greatest artificial cold 220 degrees below Fahr.

" natural " 73.7 " " "

Mercury freezes 39 " " "

Mixture of snow and salt 4 " " "

Greatest density of water at 39.2 " above "

Blood Heat 97.9 " " "

Alcohol boils 172.4 " " "

Water boils 212 " " "

Mercury boils 662 " " "

Sulphur boils 824 " " "

Silver melts 1,749 " " "

Cast iron melts 2,786 " " "

STRENGTH OF VARIOUS METALS.

The tests are made by using a cubic inch of the metal and compressing it, and by trying to draw apart a square inch of metal. Indicated in pounds.

========================+=========+============= | Tension | Compression ------------------------+---------+------------- Aluminum | 15,000 | 12,000 Bra.s.s, cast | 24,000 | 30,000 Bronze, gun metal | 32,000 | 20,000 " manganese | 60,000 | 120,000 " phosphor | 50,000 | ......

Copper, cast | 24,000 | 40,000 " wire annealed. | 36,000 | ......

" " unannealed | 60,000 | ......

Iron, cast | 15,000 | ......

" " annealed | 60,000 | 80,000 " " unannealed | 80,000 | ......

" wrought | 48,000 | 46,000 Lead, cast | 2,000 | ......

Steel castings | 70,000 | 70,000 " plow | 270,000 | ......

" structural | 60,000 | 60,000 " wire annealed | 80,000 | ......

" crucible | 180,000 | ......

Tin | 3,800 | 6,000 ------------------------+---------+-------------

FREEZING MIXTURES

===============================================+======================= |Temperature Changes |in Degrees Fahrenheit +---------+------------ Mixtures | From | To -----------------------------------------------+---------+------------ Common salt, 1 part; snow, 3 parts | 32 | zero .0 Common salt, 1 part; snow 1 part | 32 | -.4 Calcium chloride, 3 parts; snow 1 part | 32 | -27 Calcium chloride, 2 parts; snow 1 part | 32 | -44 Sal ammoniac, 5 parts; salt-peter 5 parts; | | water 16 parts. | 50 | -10 Sal ammoniac, 1 part; salt-peter 1 part; | | water 1 part | 46 | -11 Ammonium nitrate, 1 part; water 1 part | 50 | -3 Pota.s.sium hydrate, 4 parts; snow 3 parts | 32 | -35 -----------------------------------------------+---------+------------

IGNITION TEMPERATURES.

Phosphorus 120 degrees Fahrenheit Bi-sulphide of carbon 300 " "

Gun-cotton 430 " "

Nitro-glycerine 490 " "

Phosphorus, amorphous 500 " "

Rifle powder 550 " "

Charcoal 660 " "

Dry pine wood 800 " "

Oak 900 " "

POWER AND HEAT EQUIVALENTS.

In studying matters pertaining to power and heat, certain terms are used, such as horsepower, horsepower-hours, watts, watt-hours, kilowatt, kilowatt-hours, foot-pounds, joule, and B. T. U. (British Thermal Unit).

The following tables give a comprehensive idea of the values of the different terms:

1 Horsepower-hour = 0.746 kilowatt-hour = 1,980,000 foot-pounds of water evaporated at 212 degrees Fahrenheit, raised from 62 degrees to 212 degrees.

1 Kilowatt-hour = 1,000 watt-hours = 1.34 horse-power-hours = 2,653,200 foot-pounds = 3,600,000 joules = 3,420 B. T. U. = 3.54 pounds of water evaporated at 212 degrees = 22.8 pounds of water raised from 62 to 212 degrees.