IU 



MOUNTAIN BLUE. 



MOVING POWERS. 



Bid 



Inn,' 4c.. mar be recommmvied : the unprofessional reader will pro- 

 lbly find sufficient information on the subject in ' Paley's Manual of 

 Gothic Architecture,' Bloxam'i ' Principles of Gothic Architecture,' or 

 any of the other accepted guides to the study of Gothic architecture ; 

 ice aim the article* GOTHIC ARCHITECTI-RE, and NORMAN Aiinim . - 

 TIKI:. One circumstance however which ought to be mentioned is 

 that the mouldings all recede within the face of the wall (like those of 

 panels), except labels, hood-mouldings, and others, that come under 

 the general denomination of ictathrr mottltiinijt, because made to pro- 

 ject instead of recede, and therefore more exposed to rain and 

 weather. 



In regard to Grecian mouldings, it remains to be observed that 

 many of thoee which are uncarved, and therefore supposed to have 

 been quite plain, were painted with some ornamental pattern, and that 

 not unfrequently in the most brilliant colours. But this mode of 

 decoration is treated more at length in the article POLVCIIBOMY. 



Mor.NT.UN BLUE. [COLOURING MATTERS.] 



MOV MAINS. [OBOORAPHT.] 



MOVEMENT, in Music, a detached and independent portion of a 

 composition. Symphonies, concertos, quartets, sonatas, vocal pieces of 

 various kinds, Ac., are divided into portions commonly differing from 

 each other in time as well as in key, and every such portion is called a 

 movement. Most symphonies are divided into an introductory slow 

 movement, then a quick movement, an andante, a minuet, a trio, and 

 another quick movement The Pastoral Symphony of Beethoven, 

 however, consists of five movements, namely, 1, a Country Scene; 

 2, The Rivulet; 8, The Village Dance; 4, The Storm; 5, as a finale, 

 The Shepherd's Song. 



MOVING FORCE may be denned as force considered with reference 

 to the momentum it produces, in like manner as accelerating force 

 means force considered as the cause of acceleration. 



Apply continued pressure to a weight of 10 Ibs., such as will in one 

 second produce a velocity of 80 feet per second; apply another pressure 

 to a weight of 7 Ibs., such as will also in one second produce a velocity 

 of SO feet per second : the momenta produced in one second are then 

 as 10 x 80 to 7 x 50, or as 800 to 350, and the moving forces are 

 said to be in this proportion. The following equation is made the 



Moving force = mass x accelerating force ; 



but this is on the supposition that a unit of acceleration produced in a 

 unit of mass shall require the amount of pressure which is taken as the 

 unit of moving force. [MASS ; MOMENTUM.] 



The connection of momentum and acceleration are developed in 

 VELOCITY and VIBTCAL VELOCITIES. It is necessary to remind the 

 young student in mechanics that accelerating force is a mathematical 

 abstraction, the conditions of all problems which actually occur intro- 

 ducing as data not accelerating forces, but moving forces. (See third 

 law of motion, in MOTIOIC, LAWS or.) Owing, however, to the' problems 

 which usually come earliest in mechanical treatises containing only 

 accelerating forces among their data, or given laws of acceleration 

 without reference to the masses in which acceleration is produced, or 

 the pressures which produce them, the learner is not sufficiently 

 reminded of this. 



MOVING POWERS. The means employed to give motion to 

 machinery, independently of the cases in which the force of gravity is 

 applied directly, as in turning the cylinder of a clock, are the strength 

 of men and animals, the pressure of the atmosphere, the expansive 

 force of steam, and the action of wind or water. It is even possible 

 that the recently proposed actions of the galvanic fluid and of fired 

 gunpowder will in time be numbered among motive forces for impelling 

 carnages, vessels, or machines. The first and second of the powers 

 above named are treated under ANIMAL STRENGTH and ATMOSPHERIC 

 RAILWAY, and the force of steam under STKA- 



The intensity of a moving power is always estimated by the amount 

 of the resistance which is overcome and the space through which tin- 

 equivalent of that resistance is conveyed, or raised vertically, in a given 

 time. Thus, in the article on ANIMAL STRENGTH, it has been shown 

 that a man, a horse, Ac., can convey a certain weight, expressed in 

 pounds, through a certain number of miles during a working day ; and 

 the continued product of the weight, the distance, and the time has 

 been made to denote the intensity of the power, one pound being the 

 n. ilu that of distance, and one hour that of time : 

 in estimating, however, the power of an engine or machine, it is usual 

 to consider one foot as the unit of distance and one minute as tin unit 

 of time, one pound being the unit of weight ; the action of the power 

 is, moreover, supposed to be continued during all the time that the 

 machine in at work. 



Originally the larger kind of engines, except such as were impelled 

 by wind or water, were moved by the power of horses; and when other 

 agroU were employed, the gross effect of the engine was estimated by 



"ber of horses to whole action it was equivalent; bu- 

 intensity of hone-power is very variable, and some' uc e was 



t first, on that account, experienced in estimating the relative values 

 In order to establish, conventionally, this dynamical unit, 

 Mem. Boulton and Wat t ascertained from trials, purposely made, that 

 strong hone can draw 125 Ibs. at the rate of 8 miles per hour during 

 8 boon : therefore the measure of the power may be expressed ty 



8000 Ibs. ( = 125x 8x 8) drawn or raised! mile in 8 hours; or, multi- 

 ply ing by 5280, the measure is 15,840,000 Ibs. raised 1 foot in ;u 

 time. This product, being divided by the number of mini;' 

 8 hours, gives 88,000 Ibs. for the weight carried or raised 1 foot per 

 minute continually ; and the last number is now universally n ; 

 as a measure of the intensity of the power of a horse. Tin : 

 when an engine is said to have the power of any number n of horses, it 

 H understood that it is capable] of raising 33,000 it pounds' weight to 

 the height of 1 foot in every minute during the continuance of its 

 action. [HoRSE-PowER.] 



The method of estimating power -by a weight carried or raised 

 through a certain space in a certain time is capable of being applied to 

 all engines : thus, in drawing a carriage along a rood, the resistance of 

 the carriage must be equivalent to some weight ; and the react 

 the water against the paddles of a steam- vessel may always be r< pre- 

 sented by a certain weight which, if it were lifted by the wheel, would 

 oppose a resistance equal to that of the water. For the useful force of 

 steam-engines in terms of the volume of water evaporated, the pressure 

 of the steam, the length of the stroke, &c., see STEAM-ESCINK. 



Wind and water are employed as prime movers by means of the 

 momentum arising from their velocity ; and the latter, occasionally, by 

 the pressure arising from its weight. The manner in which tli 

 of wind is made to act in giving motion to vessels on tl 

 water will be fully explained under SAIL, and in producing the revo- 

 lutions of windmill sails under WIND-SAIL; it is intended, ; 

 this place, merely to explain the method of forming an 

 equilibrium for the power of on oar in giving motion to a vessel, and to 

 show the f force of water on the paddles or float-boards of wheels which 

 ore turned by that element. 



Let M N represent one side of a vessel, A B the position of the oar 

 when its blade enters the water, and E the fulcrum or side of the row- 



lock against which it presses ; then, since the vessel will move forward 

 during the time that a stroke of the oar is being mode, lot r be the 

 position of the fulcrum and c D the position of the oar at the end of 

 the stroke : if the vessel had remained at rest, the oar, at the end of 

 the stroke, would have had the position c d, which may be considered 

 as parallel to c D. 



Now, B being the centre of percussion on the blade of the oar, the 

 actual motion of B (supposed to be parallel to the keel of the vessel) 

 may be represented by B d while the movement of the vessel is E p 

 ( = Dd); and therefore BD represents the relative movement nf n. 

 The lines B D and Dd being proportional to the vd the <>ar 



and vessel, which velocities we may represent by t> and t'; v v 7 will 

 express the relative velocity of the oar, and the effective power of 

 the latter will vary with (vt/p. Let a, in square feet, be the area 

 of the blade of an oar, and let the pressure of water against a square 

 foot of surface be 1 J Ib. when the velocity is 1 foot per second; then 



-a (t> tO 1 will denote the force of the oar. 



If, for simplicity, the prow of the vessel be supposed to have the 

 form of a wedge with plane faces meeting in a vertical line, 

 water, on putting a' for the area of the whole prow and fl for the 

 inclination of each face to a vertical plane passing through the keol, we 

 shall have 



for the resistance of the water against the prow. Therefore, ?i 



the number of oars all of which are supposed to act with equal forces ; 



we have, when the vessel has acquired a terminal velocity, 



*o(-t^)'=oV 3 Bin.' e, 



from which r' may be found. The velocity of a vessel moved by oars 

 is, however, found to increase in a less ratio than the niiiiiU-r of oars. 



Th. ].mirr of the oar in rowing appears to be diminished I 

 reaction of the feet of the rowers in pressing against the foot-boards ; 

 this has a tendency to force the vessel backwards, but it 

 sated by the greater velocity which the centre of percussion in i 



. acquires. Some force, however, is lost in overcoming the 

 iiuTtia of the oar, and in bringing it forward against the air ; this last 

 force is considerable when the vessel is rowed against a high wiml, 

 though it is to a certain degree diminished by the practice of feat i 

 the oars. 



The above equation might be used to determine the velocity of a 

 vessel impeUed by steam, in which paddle-wheels are employed*, if it 

 were possible to determine, nearly, the value of na, or the number o 

 square feet of paddle which, on both sides of the vessel, are at every 



