Chap. XIX.
ATMOSPHERE AS A MOVING POWER.
1221
of cylinders which extended the whole length of the sails, and were put in motion by asystem of wheel work connected with the shaft in the following manner; — a ring of iron about4 inches wide and | of an inch thick, was attached to the main shaft, and concentric with it, ashort distance behind the whip : a bevelled wheel without arms is made to revolve easilyupon the circumference of the ring, and a spur-wheel without arms turns upon four pinsin the back of the same. The whole machinery revolves with the shaft, and when thequantity of canvas spread is too great, a lever fastened to the bracings, and weighed soas to hang vertically, is brought into a horizontal position by means of a string attached tothe end within the mill ; in this position it engages a stud upon the spur-wheel, and pre-vents its motion : a bevelled wheel then gives motion to the four small pinions, and withthem the cylinders, which continue to wind up the cloth, until the miller from within letsgo the string, and the lever is disengaged from the stud.
On the relative Effects of Hint/mill Sails, according to Smeaton and Coulomb .— The velocityof windmill sails, whether unloaded or loaded, producing a maximum effect, is nearlyas the velocity of the wind, their shape and position being similar. The load at themaximum is somewhat less than as the square of the velocity of the wind, the shape andposition of the sails being the same. The effects of the same sails at a maximum are nearly,but somewhat less than, as the cubes of the velocity of the wind. The load of the samesails at the maximum is nearly as the squares, and their effects as the cubes of the numbersof turns in a given time : when sails are loaded, so as to produce a maximum effectat a given velocity, and the velocity of the wind increases, the load continuing the same,the increase of effect, when that of the velocity of the wind is small, will be nearly as thesquares of those velocities : when the velocity of the wind is double, the effects will henearly as 10 to 27 \ ; when the velocities compared are more than double that where thegiven load produces a maximum, the effects increase nearly in the simple ratio of thevelocity of the wind. In sails where the figures and positions are similar, and the velocityof the wind the same, the number of turns in a given time will he reciprocally as theradius or length of the sail: the load at a maximum overcome by sails of a similar figureand position, at a given distance from the centre of motion, will be as the cube of theladitis.
The effects of sails of similar figure and position are as the squares of the radius: thevelocities of the extremities of Dutch sails, as well as of the enlarged sails, in all their usualpositions when unloaded, or even loaded to a maximum, are considerably quicker than thevelocity of the wind.
Number ofAle Gallonsdelivered onan OvershotWheel 10 ft.in diameterevery minute.
Diameter ofthe Cylindersof the com*mon SteamEngine ininches.
Diameter ofthe C> Underof the im-proved SteamEngine ininches.
Number ofHorses em-ployed 9jworking hrs.per day,andmoving at therate oCi milesper hour.
Numberof menworking12 hoursper day.
Radius ofDutch Sailsin their com-mon poMiionin feet.
Radius ofDutch Sails intheir bestposition infeet.
Radius ofMr.smeaton ’senlarged Sailsin feet.
Height towhich theseditlerentpowers willraise 1000 lbs.avoirdupois
minu'e.
230
8-
6 12
1
5
21 -24
17-89
15 65
13
390
9-5
7-8
2
10
30 04
25 30
22-13
26
528
10-5
8 2
3
15
36-80
30-98
27-1 1
39
GCO
11-5
8-8
4
20
42-48
35-78
31 -30
52
790
12-5
9-35
5
25
47-50
40 00
35-(’0
65
970
14-0
10-55
6
30
52-03
43-82
38-34
78
1170
15-4
11*75
7
35
56 -90
47-33
41-41
90
1350
16-8
12-8
8
40
60 09
50-60
44-27
104
1445
17-3
13-6
9
45
63-73
53-66
46-96
117
1584
18-5
14*2
10
50
67 17
56-57
49-50
130
1740
19-4
14-8
11
55
70 46
59-33
51'91
143
1900
20-2
15*2
12
60
73-59
61-97
54-22
156
2100
21-0
16-2
13
65
76*59
64 5
56 -43
169
2300
22 0
17-0
14
70
79-49
66-94
58-57
182
2500
23-1
17-8
15
75
82-27
6928
60-62
195
2686
23-9
18-3
16
80
84-97
71 55
62 61
208
2870
24-7
19 0
17
85
87-07
73 32
64-16
221
3055
25-5
19-6
18
90
901 3
75-90
67-41
234
3240
26-2
201
19
95
92-60
77-98
68 23
247
3240
27 0
20-7
20
100
95*00
80-00
7000
2 r 0
3750
28-5
22-2
22
I 10
99-64
83-90
73-42
2S6
4000
29-8
23 0
24
120
104 06
87-63
76-68
312
4460
31-1
23-9
26
130
108 -32
91 22
79-81
338
4850
32-4
24-7
28
140
112-20
94-66
82-82
364
5250
33-6
25-5
30
150
1 1635
97-98
85-73
390
4 i 3