Cal. pr.—Ther. units per lb.: Coal, 14,300;
petrol’m, 20,000; coal gas per cu. ft., 700.
Sp. heat:—Wt. iron, 0·1138; C.I., 0·1298;
copper, brass, 0·095; lead, 0·0314.
Inch = 25·4 mil’metres; mil’metre = 0·03937 in.
Foot = 0·3048 metres; metre = 3·2809 feet.
Yard = 0·91438 metre; metre = 1·0936 yards.
Mile = 1·6093 kilomtrs.; kilomtr. = 0·6213 mile.
Sq. in. = 6·4513 sq. cm.; sq. cm. = 0·155 sq. in.
Sq. ft. = 9·29 sq. decmtr.; sq. decmtr. = 0·1076 sq. ft.
Sq. yd. = 0·836 sq. metre; sq. metre = 1·196 sq. yds.
Sq. ml. = 258·9 hectares; hectare = 0·00386 sq. ml.
Cu. in. = 16·386 c. cm.; c. cm. = 0·06102 cu. in.
Cu. ft. = 0·0283 c. metre; c. metre = 35·316 cu. ft.
Grain = 0·0648 gramme; gram. = 15·43 grs.
Ounce = 28·35 grams.; „ = 0·03527 oz.
Pound = 0·4536 kilogm.; kilogm. = 2·204 lb.
Ton = 1·016 tonnes; tonne = 0·9842 ton.
Mile per hr. = 1·466 ft., or 44·7 cm., per sec.
Lb. per cu. in. = 0·0276 kilogram per cu. cm.
Kilogram per cu. cm. = 36·125 lb. per cu. in.
Lb. per cu. ft. = 16·019 kilogm. per cu. mtre.
Grain per gall. = 0·01426 gramme per litre.
Gramme per litre = 70·116 grains per gall.
Ultimate Strength│Lb. per Sq. in.
„ │Tens’n.│Comp’n.
─────────────────┼───────┼───────
Wt. iron │ 50,000│ 50,000
Cast „ │ 16,000│ 95,000
Steel │ 80,000│ 70,000
Copper │ 21,000│ 50,000
Brass │ 18,000│ 10,500
Lead │ 2,500│ 7,000
Pine │ 11,000│ 6,000
Oak │ 15,000│ 10,000
Weight of Metals.│ Cub. In. │ Cub. Ft. │12 Cu. In.
─────────────────┼──────────┼──────────┼──────────
Wt. iron │ 0·277│ 480│ 3·33
Cast „ │ 0·260│ 450│ 3·12
Steel │ 0·283│ 490│ 3·40
Copper │ 0·318│ 550│ 3·82
Brass │ 0·300│ 520│ 3·61
Zinc │ 0·248│ 430│ 2·98
Alumin’m │ 0.096│ 168│ 1·16
Lead │ 0.411│ 710│ 4·93
Lb. per sq. in. = 2·31 ft. water = 2·04 in. mercury = 0·0703 kilo. per
sq. cm.
Atmosphere = 14·7 lb. per sq. in. = 33·94 ft. water = 1·0335 „ „
Ft. hd. water = 0·433 lb. per sq. in. = 62·35 lb. per sq. ft. = 0·0304 „
„
Cub. ft. of water = 62·35 lb. = 0·0278 ton = 28·315 litres = 7·48 U.S.
galls.
Gall. (Imp.) = 277·27 cu. in. = 0·1604 cu. ft. = 10 lb. water = 4·544
litres.
Litre = 1·76 pints = 0·22 gall. = 61 cu. in. = 0·0353 cu. ft. = 0·264
U.S. gall.
Horse-power = 33,000 ft.-lb. per min. = 0·746 kilowatt = 42·4 heat units
per min.
Heat unit = 778 ft.-lb. = 1055 watt-sec. = 107·5 kilogrammetres = 0·252
calorie.
Foot-pound = 0·00129 heat unit = 1·36 joules = 0·1383 kilogrammetres.
Kilowatt = 1·34 H.P. = 44,240 ft.-lb. per min. = 3412 heat units per
hour.
-----
Footnote 1:
It will be recognised that n is the characteristic of the logarithm of
the original number.
Footnote 2:
The special case in which the numerator is 1, 10, or any power of 10
must be treated by the rule for reciprocals (page 27).
Footnote 3:
The possible need for traversing the slide, to change the indices,
when using the C and D scales, is not considered as a setting.
Footnote 4:
The reader may be reminded that cross-multiplication of the factors in
any such slide rule setting will give a constant product, _e.g._, 20 ×
94·5 = 27 × 70.
Footnote 5:
In this case cross _dividing_ gives a constant quotient, _e.g._, 8 ÷ 3
= 4 ÷ 1·5. Since the upper scale is now a scale of reciprocals, the
ratio is really
O ⅛ ¼
───────────
D 1·5 3
Footnote 6:
These lines should not be brought to the working edge of the scale but
should terminate in the horizontal line which forms the border of the
finer graduations, their value being read into the calculation by
means of the cursor (see page 55).
Footnote 7:
The same principle may be applied to the cursor.
Footnote 8:
Philosophical Transactions of the Royal Society, 1815.
------------------------------------------------------------------------
_BY THE SAME AUTHOR._