1092

THEORY AND PRACTICE OF ENGINEERING.

Book II.

and inertia, which is probably the case in this machine, where the construction is simple andcarefully executed.

The Horse considered as a Mover. Of his Swiftness -The greatest swiftness of a horse

in a course of 7 or 8 minutes is 12 to 15 metres per second. Bouvard observed that inthe Champ de Mars at Paris , a horse mounted by a cavalier on a smooth road winding inthe form of the figure of an eight, went over 2575 metres in S' 31", or 211". In theNewmarket races a horse has gone over 6784 metres in 7' 30": a horse harnessed ina cart has gone over 1478 metres in 2' 13" on a road in the form of an eight, in theChamp de Mars .

These three experiments gave for the swiftness of the horse in l ,r ,

1st experiment - 12-21 metres.

2 _ - - - 15* —

3 — ... 11-11 —

We are assured that a harrier is capable of following the best English horse, and thatthe reindeer attached to a sledge runs at the rate of 8 metres per second.

Cavalry makes in a minute,

at the common pace - - 120 steps, and goes over - 100 metres,

trot ... 180 — — - 200 —

gallop - 200 — — - 320 —

which gives for the ordinary length of a horse’s step 0*83 metres, for the velocity corre-sponding to this pace 1*66 metres per second ; for the velocity at a trot 3*3 metres; and ata gallop 5-3.

It has been remarked that the pace of a man more or less accelerated is always nearly ofthe same length : the inequality of a horse’s step proves that he throws out his legs inrunning, and clears a space which must be added to his ordinary step. Bose saw in N.America savages who leapt while walking, and he assures us that this manner of proceedingwas very favourable for an accelerated and continuous velocity, and also fatigues less thanany other.

A good hotse loaded with about 80 kilogrammes, including the weight of the rider, candaily go over 40 kilometres (25 miles English ) in 7 or 8 hours, which gives from 1-4 metresto 1 -5 metres per second. The weight of a horse of mean strength is 225 to 250 kilo-grammes.

The tractive Power and Load of a Horse .—In contracts for carting, we generally calculatethe load of the carts at 700 to 750 kilogrammes to a horse, without comprising the weightof the cart: the tractive power of a good waggon horse is 140 kilogrammes ; a team goesover on a good horizontal road 38 to 40 kilometres in 8 or 9 hours ; at 40 kilometres in 8hours the velocity is 1 -4 metres in a second.

Horses attached to diligences going at a trot, and making a post or 8 kilometres in anhour, go over daily 34 to 38 kilometres : the tractive power of each is about 90 kilogrammes ;their velocity is 2-2 metres in 1".

The daily action of the horse of a waggon being expressed by the product of two numbers,90 kilogrammes and 38 kilometres, these two actions are in the relation of 5600 to 3420,or 163 to 100. These experiments give 100 kilogrammes as the mean tractive power ofhorses.

Of the Strength of the Horse taken as a dynamic Unit. — The constructors of steam-enginesestimate the power of these machines in dynamic units, each of which measures the strengthof a horse when harnessed. Let us suppose that a horse is capable of moving a mass of140 pounds with a velocity of 200 feet in a minute: this dynamic effect is 28000 poundselevated 1 foot, or 4149 kilogrammes i metre ; according to this definition, the strength of ahorse working 24 hours continuously is equivalent to 5974 units, each the weight of 1 cubemetre of water elevated 1 metre; or, 5974 x 2208 pounds avoirdupois raised 3-281 feetEnglish .

Machine of Mr. Gonin Dyer, Rue Blanche Castile, Isle St. Louis . — This machine has onehorse, which works 5 or 6 hours a day in three relays ; in 1 hour he lifts by means of a pump28 muids of water, each muid being 268 litres 13 metres high, or 97.j cube metres to aheight of 1 metre, which gives for the daily labour of 6 hours in the 24, 585 metres ofwater elevated 1 metre.

Machine near Paris over a Plaster Quarry _This machine has one horse which works

12 hours a day; the effect is to elevate by means of a drum 96 casks of plasterfrom the bottom of the quarry to a height of 23 4 metres; each cask weighs about 375kilogrammes, and the weight of the plaster elevated in a day is equal to 36 cube metres ofwater, which gives 842 dynamic units for the daily action.

The horse harnessed to the extremity of a lever 3*575 metres long goes over in a minutea circle of 22*4 metres, in a second an arc of 37 centimetres, and in 10 hours of labour13*4 kilometres.

The cask is elevated in 7] minutes ; at each ascension the horse stops to change thedirection of his rotatory movement: supposing the duration of effective labour to be 10