USEFUL 
MEMORANDA AND HINTS. 
91 
F “om our Directory we take useful hints worthy of repetition here :— 
From “MoLteswortnH’s Pocket—Book oF ENGINEERING ForRMULz.”’ 
[Extracted by permission of the Author] 
SEEN 
ASPHALTE FLOORING. 
8 lb. of asphalte composition will cover 
1 sup. foot, ? inch thick. 
CORRUGATED IRON ROOFING. 
nl 
3 e 
B. Wire a Weight per} & 
Gauge. square. = 
2 a 
2 w 
Feet. ewt. qrs. lb. 
No. 16...16%2t08%3]}1 0 14) 800 
18...\1642t08n%3|1 1 6 | 1000 
20....6%2to8x3 /1 3 6 | 1250 
22...16%2to7# 22! 1 2 7 \ 1550 
24...1642t07*%23|1 0 24 | 1880 
26....642to7*23|.1 0 6 | 2170 
1-10th of the weight to be added for 
lappage. 
Sheets should overlap about 6 inches, 
and be double rivetted at joints. 
3 lbs. of rivets required per square of 
roofing. : 
Purlins should be 6 feet apart. 
Curved roofs may be made up to 20 
feet span without framing; tie-rods 12 
feet apart. 
SOUND. 
Velocity of sound in air...= 1,142 ft. per 
[second. 
Ditto BS water — 4,900 _ ,, 
Ditto a trom = —— VEO: as. 
Ditto 4 copper—10,378 _,, 
Ditto ap wood =12,000 ,, 
to 16,000 ,, 
Distance sounds may be heard on a 
still day: 
Human voice......... 150 yards. 
Hille dnsseees eee -cs. 00” 
Military band ...... OLN) he 
Gannon... <c.ccssses509,000* 8 
HEAT. 
Conducting power of substances, slate 
being 1000. 
3) BUG coscceccucesacn Fire-brick ...... 620 
Ailes oepelessieaeiese Cita iss caceostee nites 
Flagstone Asphalte......... 
Portland stone.. 750} Oak . = a6 
Brick.....+00+..... 600 | Lath and plaster 255 
to 730 | Cement ......... 200 
GLUE TO RESIST MOISTURE. 
1 Ib. of glue melted in 2 quarts of 
skimmed milk, 
When strong glue is required add 
powdered chalk to common glue, 
GLUE CEMENT TO RESIST MOIST- 
URE. 
le - : 
1 pee rosin (mixed with the least pos- 
1 red ochre sible quantity of water. 
OR 
4 of glue. 
1 of boiled oil by weight. 
1 oxide of iron. 
ADMIRALTY KNOT=6080 FEET. 
Marine paddle-engines generally work 
up to 3 times nominal horse-power; screw 
engines (direct action) to 4 times. 
WATER POWER. 
Theoretical horse-power of water: 
Q—Quantity of water, in cube feet, per 
minute. 
h—Head of water from tail-race, in fect, 
HP=—Theoretical horse power. 
HP—.00189 Q h. 
528 HP 
Qa 
h 
Effective horse-power for different 
motors: 
Theoretical power being,..............—=1.00 
Undershot water-wheels ...........— «35 
Poncelet’s undershot water-wheels— .60 
IBTEASG WICCLEER SS scatter nuevos sadcanicceeees “55 
Eig A-Dreast He s.ns.sastoscescnes « ae 
Overshot wheel aessbees=— -.68 
PUT DINE Heer. Mio cspat sconces sete 70 
Hydraulic ram rising water.........__ .60 
Water-pressure engine.........00+...— .80 
MEMORANDA CONNECTED WITH WATER. 
1 cubic foot of water—62.4 lb. 
1 eubic inch ......... =—=05001p: 
LT gallon i...........0.==l0Ib. 
OL .eeeee secsescerseeeee——0.16 cube feet. 
1 cube foot of water —6.2355 gallons. 
or, approximately —6+ és 
1 ewt. of water......—1.8 cube ft.=11.2 gals. 
1 ton of water.)..... =—=89.9 cube ft.—224 ,, 
Pressure of water per sq.inch at different 
heads: 
P—Pressure in lb. per square inch. 
H—Head of water, in feet. 
P—H » .4833. 
H—P 2.31. 
Pressure per square foot—H 62.4. 
Cubic feet of water x 0.557—ewt. approxi- 
[mately. 
x <2 4 0.028—tons 5 
1 cube foot of sea water...—64.14 lb. 
Weight of sea water—weight of fresh 
water ® 1:028. 
