Page images
PDF
EPUB

ginal method, in which all large subjects were “ The demi-tints are of an olive grey, or of done imunediately after the discovery of the art a yellowish or reddish cast, and the shades of of expressing forins and substances, by the ju- red, mixed with black. The draperies, in gedicious disposition of different coloured earths neral, are made with little plaits, formed of diluted with water. Savages found in a com- light and flexible stuffs, after the style of Roplete state of nature, who knew nothing more man seulpture.” The picture of Télephus is, ihan her immediate dictates, have been found however, an exception, and seems to lead the covered with colours, collected, and used on author to think, that the artist who performed their persons by instinct; and some have even this piece was superior to those who executed demonstrated genius, in working the beautiful the others. mantles and helmets formed of feathers of the In the aggregate there are no groupes, harmost vivid tints: one step more would have muny, or claro obscuro. Each figure stands, produced painting on walls, but it was reserved as it were, independent, with its own light and for the ancient Grecians to enlighten and bene- shade only, neither receiving reflected light fit the world by the superior talents they had from the next, nor casting shade on it; nor received and cultivated. It would be vain are the shades broken, but done with the same to enter into an investigation when their át- colour as the half tints, and hare merely less tempts arrived to that state of comparative per- white. This peculiarity arose from their defifection, which produced the delineation of ciency in the science of perspective, which refyures on plaster or similar composition; we duced the artist to the necessity of making the must, therefore, be satisfied with describing graduation of distance by the faintness of his some still extant of very great antiquity, and colours. “ For the rest,” adds the count," the mentioning the modern method of using the pictures are done with ease, the touch is bold, colours.

and the pencil handled freely, the colouring It may reasonably be supposed, that the first being sometimes laid on patches, and somepictures painted in this way were extremely times softened down ; in a word, the execurude, and probably did not consist of more than tion is light, and in the saine style nearly as two colours, a light one for the ground, and a we paint the decorations of our theatres, the dark for the outlines; for blending the tints whole indicating a great practice in the are must have been the result of experience, and tists." some degree of freedom. This supposition Thus much is considered necessary, in order may be illustrated by referring to the valuable to show that the adoption of many colours in vases brought from Herculaneum, by the late fresco paintings took place subsequent to 471; sir William Hamilton, and now deposited in like all other arts, it must have been improved the British Museum. Those, and the paintings by degrees, and it cannot be doubted, that the found in the same city, were in all probability great masters, whose labours still adorn the the performances of Italians : but as the art numeroas churches and palaces in Italy, conwas then evidently in its infancy, the Greeks tributed largely to its perfection; though it is might not have excelled their imitators. In- well known that inany of their best works have deed painting must have been considered by suffered from damps, which it is presumed that ingenious people as an art inferior to that will prevent their stability wherever it prevails. of sculpture, which accounts for the superior This circumstance has operated to so great a deexcellence, and earlier improvements, in the gree in St. Peter's at Rome, that most of the bauer.

old pictures have been replaced by others in The appendix to the abbé Barthelemy's tra- mosaic. See Mosaic. rels in Italy cootains several curious remarks The same cause has prevented the frequent on Herculaneum, by count Caylus and others, use of fresco painting in England, except in and Du Theil : the latter supposes that the de- mansions where a dry air is constantly preservstruction of this city happened in the year 471, ed. The necessity of this precaution is deinonCaylas, on treating upon the ancient paintings strated at present in the dome of St. Paul's. discovered, observes, “ As to their designing, The manner of performing this description of it is dry, and hardly ever exceeds the idea of a painting, is to work while the plaster is wet fine statue. The composition is in general which covers the wall to be decorated; couisecold, for the same reason that the design is dry. quently, in the execution of large subjects, the In fact, a figure is not grouped, though it be process of plastering must immediately precede placed with others; and statues, intended at the brush of the artist, and only in the propotfirst to stand alone, will with difficulty enter tion he works, that the colours may incorpo into composition without some alteration ; rate with the composition, and that it may not though the Diana in the Tliesus, and the wo- absorb the water which dilutes them, and preman with wings in the Telephus, are more vent the free touches intended for effect. contrasted, and have an air of motion.

Vitravius, who calls fresco painting udo "The general taste of the composition is re- rectorio, gives an accurate account of the ex: markable, not only for its resemblance to sta- treime care which the ancients thought necestues, as I have observed before, but to bas sary in preparing the stuccoes for the colours, reliefs also. It is clear that the authors had and it must be admitted that they succeeded them present to their imagination, and that admirably, when we consider how very perthey had made on their minds a very lively fect the remains of their productions

now are, impression,

after undergoing the sulphureous inhumation of ashes, caused by the eruption of Vesuvius, great hardships, owing to his having adopted one thousand three hundred and thirty-seven a profession contrary to the wishes of his payears past. The moderns, however, conceive rents. However he persevered in his studies, ihat their lime and sand is preferable. and while he was employed in copying the

The design intended for a wall should be works of the best masters, he planned a Latin drawn on paper, or any substance from whence poem, De Arte Graphica, which was afterit may be transferred to the wet plaster; the wards published. This ingenious man died mode of proceeding must afterwards be similar in 1665. His poem was printed after his to that practised in painting upon canvas. death, with a prose translation, by de Piles, The colours should be earths, exclusively, di- with notes. It has been rendered into Enluted with water sufficiently to make them glish, first by Dryden, and lastly by Mr. Maflow freely, but not to decompose the plaster son. Fresnoy, as a painter, imitated Titian. and mix its surface with them; long soft FRET. s. fretum, Latin.) 1. A frith, or haired brushes should therefore be preferred. strait of the sea, where the waler by confine(Brit. Ency.).

ment is always rough (Brown). 2. An agitaFRESH. a. (fresc, Saxon.) 1. Cool; not tion of liquors by fermentation, or other cause rapid with heat (Prior). 2. Not salt (Abbot). (Derhum). 3. Work rising in protuberances 3. New; not had before (Dryden). 4. New; (Spectator). 4. Agitation of the mind; comnot impaired by time (Milton). 5. In a state motion of temper (Herbert). like that of recentness (Denham). 6. Recent; Fret, or FRETTE, in architecture, a kind newly come (Dryden). 7. Repaired from any of knot or ornament, consisting of two lists or loss or diminution (Dryden). 8. Florid ; vi- sınall fillets variously interlaced or interwoven, gorous; cheerful; unfaded; unimpaired (Ba- and running at parallel distances equal to their con). 9. Healthy in countenance; ruddy breadth. ă necessary condition of these frets (Harvey). 10. Brisk; strong; vigorous (Hol- is, that every return and intersection be at der). 11. Fasting : opposed to eating or drink- right angles. This is so indispensable, that ing. 12. Sweet: opposed to stale or stinking. they have no beauty without it, but become Fresh. s. Water not salt (Shakspeare). perfectly Gothic.

T. FRESHEN. v. a. (from fresh.) To FRET-WORK, that adorned with frets. It make fresh (Thomson).

is sometimes used to fill up and enrich flat To Fre'shen. v. n. To grow fresh (Pope). empty spaces; but it is mostly practised in

FRESHES, among sailors, the violence of roofs, which are fretted over with plaister an ebb-tide, increased by heavy rains, flowing work. into the sea, which it discolours to a consider- FRETS, certain short pieces of wire fixed able distance from the shore on such occasions, on the finger-board of guitars, &c. at right where the line on which the two colours meet angles to the strings, and which, as the strings may be distinctly observed for a great length are brought into contact with them by the along the coast.

pressure of the fingers, serve to vary and deterFRE'SHET. s. (from fresh.) A pool of mine the pitch of the tones. fresh water (Milton).

To Frét. v. a. (from the noun.) 1. To FRE'SHLY. ad. (from fresh.) 1. Coolly. agitate violently by external impulse or action 2. Newly; in the former state renewed (Ba- (Shakspeare). 2. To wear away by rubbing con). 3. With a healthy look; ruddily (Shak. (Neuton). 3. To hurt by attrition Milton), speare).

4. To corrode ; to eat away (Hakewill): 5. FRESHNESS. s. (from fresh.) 1. New- To form into raised work (Milton). 6. To ness ; vigour ; spirit; the contrary to vapidness variegate ; to diversify_(Shakspeare). 7. To (Bacon). 2. Freedom from diminution by make angry; to vex (Ezekiel). time; not staleness; not decay (South). 3. TO FRET. v. n. 1. To be in commotion; Freedom from fatigue; newness of strength to be agitated (South). 2. To be worn away; (Hayward). 4. Coolness (Addison). 5. Rud- to corrode (Peach.).' 3. To make way by aidiness; colour of health (Granville). 6. Free- trition (Moron). 4. To be angry; to be dom from saltness.

peevish (Pope). FRESNE (Charles du Cange du), a learned FRETFUL. (from fret.) Angry; peevish. Frenchman, born at Amiens in 1610. He FRETFULLY. ad. Peevishly. was bred to the law, and became advocate in FRETFULNESS. s. (from fretful.) Pasthe parliament of Paris. He compiled a glos- sion; peevishness. sary of low Latin, intitled, Glossarium Mediæ FRÉTTY. a. (from fret.) Adorned with et 'infimæ Latinitatis, which has been fre- raised work. guently, printed. The best edition is that of FREUDENSTADT, a strong town of SuaHalle, in 6 vols. 8vo. 1772-1784. His Greek bia, in the Black Forest, built to defend the Glossary of the middle Age, in 2 vols. folio, passage into this forest. It is 12 miles S. E. of is also ani esteemed work. He also published a Strasburg. Lon. 8. 21 E. Lat. 48. 28 N. History of Constantinople, and various other FREYBERG, or FRIEDBERG, a town of books, and died in 1688.

Upper Saxony, containing above 60,000 inha. FRESNOY (Charles Alphonsus du), a bitants. In the environs are mines of copper, French painter and poet. He was born at Pa- tin, lead, and silver, which employ a great ris in 1611, and having studied under Perrier number of workmen, and produce above Vouet, he went to Rome, where he suffered 10,000 rix-dollars a-year. Here is the usual burying-place of the princes of the electoral of its privileges, and at last purchased its freehouse of Saxony. It is situate on a branch of dom for 20,000 marks of silver. This sum the Muldau, 15 miles S.W .of Dresden. Lon. was advanced by the house of Austria, by 11.10 W. Lat. 51. O N.

which means the town became subject to that FREYSINGEN, a town of Germany, ca- family. It was formerly an important fortress, pital of a bishopric of the same name, in the but being taken several times by the Swedes circle of Bavaria. It was taken by the French and the French, it was dismantled by the latin 1796. It is seated on a mountain, near the ter, in the year 1744. The streets are broad Iger, 20 miles N. by E. of Munich. Lon. 11. and well paved. The principal church is a 50 E. Lat. 48. 26 N.

superb edifice.

Here is a university, founded FREZIERA. In botany, a genus of the in 1457, by Albert IV. duke of Austria, with class polyandria, order monogynia. Calyx five- an academy and five colleges depending on it. leared ; petals five; style trifid; berry juice. Here are, besides ten convents, a commandery less, many-celled, many-seeded. Two species : of the Teutonic order, and thirteen churches. one a native of Jamaica, the other of the East Lat. 48. 10 N. Lon. 7.57 E. Indies.

FRICASSE’E. s. (French.) A dish made FRIABI'LITY. s. (from friable.) Capaci- by cutting chickens or other small things in ty of being easily reduced to powder (Locke). pieces, and dressing them with strong sauce.

FRIABLE.'a. (friable, French.) Easily FRICATION. s. (fricatio, Latin.) The crumbled; easily reduced to powder (Bacon), act of rubbing one thing against another

FRIAR, or FRIER, by the Latins called (Bacon). frater, the Italians fra, and the French frere, FRICTION. s. (frictio, Latin.) 1. The that is, lroiher: a term common to the monks act of rubbing two bodies together (Newton). of all orders; founded on this, that there is a 2. The resistance in machines caused by the kind of fraternity or brotherhood presumed be- motion of one body upon another. 3. Meditween the several religious persons of the same cal rubbing with the fleshbrush or cloths (Baconrent or monastery;.

con). Friar's Cowl. See Arum. FRI'ARLIKE. a. (from friar.) Monastic; rubbing or grating the surfaces of bodies against

Friction, when expressive of the act of unskilled in the world (Knolles).

or over each other is called also attrition. FRI'ARLY. a. (friar and like.) Like a The phænomena arising from the friction of di. friar, or man untanght in life (Bacon). vers bodies, under different circumstances, are

FRI'ARSCOWL. s. (friar and cowl.) A very numerous and considerable. Mr. Hawksbee plant that produces a Rower resembling a gives a number of experiments of this kind; parcowl.

ticularly of the attrition or friction of glass, under FRI’ARY. s. (from friar.) A monastery or various circumstances; the result of which was, convent of friars.

that it yielded light, and became electrical InFRI'Ary. a. Like a friar (Camden).

deed all bodies by friction are brought to conceive To FRI'BBLE. v. n. To trifle (Hudibras).

heat; many of them to emit light; particularly a FRI’BBLER, s. A trifler (Spectator).

cat's back, sugar, beaten sulphur, mercury, sea

water, gold, copper, &c. but, above all, diamonds, FRIBURG, one of the cantons of Swisser, which when briskly rubbed against glass, gold, or land, surrounded on all sides by the canton of the like, yield a light equal to that of a live coal Bern. It is fertile in corn, fruits, and pastures. when blowed by the bellows. Its length is about 40 miles, and breadth 20. FRICTION, in mechanics, denotes the resistance

FRIBURG, a town of Swisserland, capital a moving body meets with from the surface on of a canton of the same name. The public which it moves. Friction arises from the roughbuildings, especially the cathedral, are very ness or asperity of the surface of the body moved handsome. The inhabitants are papists. It on, and that of the body moving : for such suris governed in spirituals by the bishop of Lau- faces consisting alternately of eminences and cavisanne, who resides here, and in temporals,

by ties, either the eminences of the one must be rais2 council, over which an avoyer presides. Its ed over those of the other, or they must be both

broken and worn off: but neither can happen situation is very extraordinary, for part of it is without motion, nor

can motion be produced withbuilt on an elevated rock, part of it in a deep out a force impressed. Hence the force applied valley, and towards the west it occupies a small to move the body is either wholly or partly spent plain. The streets are irregular, steep, clean, on this effect; and consequently there arises a reand tolerably wide; the houses are well built, sistance or friction, which will be greater as the and soine of them handsome; there are several eminences are greater, and the substance the hardchurches and convents. It is surrounded with er; and as the body, by continual friction, be. walls, towers, and sharp rocks. Friburg con- comes more and more polished, the friction dimitains some manufactures, but none that are

nishes. important. Lat. 46. 48 N. Lon. 6. 53 E. M. Amontons was the first philosopher who fa.

FRIBURG, a town of Germany, in the cir- voured us with any thing like correct information cle of Swabia, and capital of the Austrian Bris- upon this subject. He found that the resistance gaw, situated at the foot of a stony mountain, tal surface was exactly proportional to its weight,

opposed to the motion of a body upon a horizonon the river Traisam, founded in the year 1118, and was equal to one third of it, or more generally by Berthold III, duke of Zahringen, from to one third of the force with which it was pressed whom it came to the counts of Furstenberg, against the surface over which it moved. He diswith whom it had many disputes on account covered also that this resistance did not increase YOL. V.

1

Mx W x 8, where M is the

[ocr errors]

with an increase of the rubbing superficies, nor The Abbé Nollet an: Bossnt have distinguishel with the velocity of its motion.

friction into kinds, that which arises from one The experiments of M. Bulfinger authorized surlace being dragged orer another, and that conclusions similar to those of Amontons, with which is occasioned by one body rolling upon this difference only, that the resistance of friction another. The resistance which is generated by was equal only to one fourth of the force with the first of these kinds of friction is always greater which the rubbing surfaces were pressed together. than that wbich is produced by the second;

This subject was also considered by Parent, and it appears evidently from the experiments of who supposed that friction is occasioned by small Muschenbroek, Schweber, and Meister, that when spherical eminences in one surface being dragged a body is carried along with an uniformly acceleout of corresponding spherical cavities in the rated motion, and retarded by the first kind of other, and proposed to determine its quantity by friction, the spaces are still proportional to the finding the force which would move

a sphere stand- squares of the times, but when the motion is affecting upon three equal spheres. This force was ed by the second kind of friction, this proportionfound to be to the weight of the sphere as 7 to 20, ality between the spaces and the times of their or nearly one third of the sphere's weight. In in- description does not obtain. vestigating the phenomena of friction, M. Pareut The subject of friction has more lately occupi. placed the body upon an inclined plane, and aug- ed the attention of the ingenious Mr. Vince of mented or diminished the angle of inclination till Cambridge. He found that the friction of hard the body had a tendency to more, and the angle bodies in motion is an uniformly retarding force, at which the motion commenced be called the and that the quantity of friction considered as angle of equilibrium. The weight of the body, equivalent to a weight drawing the borly backtherefore, will be to its friction upon the inclined plane as radius to the sine of the angle of equili- wards is equal to M brium, and its weight will be to the friction on a horizontal plane as radius to the tangent of the moving force expressed by its weight, w the equilibrium.

weight of the body upon the horizontal plane, S The celebrated Euler seems to have adopted the the space through which the moving force or hypothesis of Bulfinger respecting the ratio of weight descended in the time i and r=16.087 feet, friction to the force of pression; and in two curi- the force of gravity. Mr. Vince also found that ous dissertations which he has published upon the quantity of friction increases in a less ratio this subject, has suggested many important obser- than the quantity of matter or weight of the body, vations, to which Mr. Vince seems afterwards to and that the friction of a body does not continue have attended. He observes, that when a body is the same when it has different surfaces applied to in motion, the effect of friction will be only one the plane on which it moves, but that the smallhalf of what it is when the body has begun to est surfaces will have the least friction. move; and he shews that if the angle of an in- Notwithstanding these various attempts to uniclined plane be gradually increased till the body fold the nature and effects of friction, it was rewhich is placed upon it begins to descend, the served for the celebrated Coulomb to surmount friction of the body at the very commencement of the difficulties which are inseparable from such an its motion will be to its weight or pressure upon investigation, and to give an accurate and satisthe plane as the sine of the plane's elevation is to factory view of this complicated part of mechaits cosine, or as the tangent of the same angle is nical philosophy. By employing large bodies .to radias, or as the height of the plane is to its and ponderous weights, and conducting his expelength. But when the body is in motion the fric- riments on a large scale, he has corrected seves tion is diminished, and may be found by the fol. ral errors which necessarily arose from tle limite

ed experiments of preccding writers ; he has lowing equation p=tan. a.

in which 15625nn cos. a

brought to light many new and striking phenome. pe is the quantity of friction, the weight or pres. na, and confirmed others which were hitherto sure of the body being -1, á is the angle of the but partially established. As it would be foreign plane's inclination, m is the length of the plane to the nature of this work to follow monsieur in 1000th parts of a rhinland foot, and n the time Coulomb through his numerous and varied expeof the body's descent. Respecting the cause of riments, we shall only present the reader with the friction, Euler is nearly of the same opinion with

new and interesting results which they authoParent; the only difference is, that instead of rized. regarding the eminences and corresponding de

1. The friction of homogeneous bodies, or bopressions as spherical, he supposes thein to be an. dies of the same kind moving upon one another is gular, and imagines the friction to arise from the generally supposed to be greater than that of body's ascending a perpetual succession of in heterogeneous bodies; but Coulomb has shevu clined planes.

that there are exceptions to this rule. He found, Mr. Ferguson found that the quantity of friction for example, that the friction of oak upon oak

1 was always proportional to the weight of the rub

was equal to of the force of pression; the bing body, and not to the quantity of surface, and

2.34 that it increased with an increase of velocity, but

and of oak was not proportional to the augmentation of cele- friction of pine against pine was

1.78' rity. He found also that the friction of smooth soft wood, moving upon smooth soft wood, was against pine The friction of oak against cop

1-5 equal to ļ of the weight; of rough wood upon

1 rough wood of the weight; of soft wood upon per was and that of oak against iron nearly hard, or hard upon soft, of the weight; of

5.5' polished steel upon polished steel or pewter 4 of the same. the weight; of polished steel upon copper, and 2. It was generally supposed, that in the case of polished steel upon brass of the weight. of wood, the friction is greatest when the bodies

1

[ocr errors]

was

1

only 3.76

are dragged contrary to the conrse of their fibres; when a smaller surface was used, the frietion inbut Coulomb has siewn that the friction is in this stead of being greater, as might have been exa case sometimes the smallest. When the bodies

1 moved in the direction of their fibres the friction pected, was only

2.19 of the fibres with which they were

6. Friction for the most part is not augmented 2-34

by an increase of velocity. In some cases, howpressed together; but when the motion was con- ever, it is diminished by an augmentation of celetrary to the course of the fibres, the friction was rity.-M. Coulomb found, that when wood moved

upon wood in the direction of the fibres, the fric

tion was a constant quantity, however much the 3. The longer the rubbing surfaces remain in velocity was varied; but that when the surtaces contact, the greater is tbeir friction. - When were very small in respect to the force with vood was moved upon wood, according to the di- which they were pressed, the friction was dimirection of the fibres, the friction was increased by nished by augmenting the rapidity: the friction, keeping the surfaces in contact for a few seconds; on the contrary, was increased when the surfaces and xben the time was prolonged to a minute, were very large when compared with the force of the friction seemed to have reached its farthest li- pression. When the wood was mored contrary mit. But when the motion was performed con- to the direction of its fibres, the friction in every trary to the course of the fibres, a greater time case remained the same. If wood is moved upon was necessary before the friction arrived at its metals, the friction is greatly increased by an inmaximum. When wood was moved upon metal, crease of velocity; and when metals move upon the frietion did not attain its maximum till the wood besmeared with tallow, the friction is still sarfaces continued in contact for 5 or 6 days; augmented by adding to the velocity: When meand it is very remarkable, that when wooden sur

tals move upon metals, the friction is always a faces were anointed with tallow, the time requi- constant quantity; but when heterogeneous subsite for producing the greatest quantity of friction stances are employed which are not bedaubed is increased. The increase of friction which is with tallow, the friction is so increased with the generated by prolonging the time of contact is so velocity, as to form an arithmetical progression great, that a body weighing 1650 pounds was

when the velocities form a geometrical one. moved with a force of 64 pounds when first laid

7. The friction of loaded cylinders rolling upon apon its corresponding smface. After having re- a horizontal plane, is in the direct ratio of their mained in contact for the space of 3 seconds, it weights, and the inverse ratio of their diameters. required 160 pounds to put it in motion, and In Coulomb's experiments, the friction of cylinvben the time was prolonged to 6 days, it could ders of guaiacum wood, which were two inches in searcely be moved with a force of 622 pounds. diameter, and were loaded with 1000 pounds, was When the surfaces of metallic bodies were moved 18 pounds or La of the force of pression. In cyupon one another, the time of producing a maxi- linders of elm, the friction was greater by , and mum of friction was not changed by the interpo

was scarcely diminished by the interposition of sition of olive oil ; it was increased, however, by tallow, employing swines grease as an unguent, and was

From a variety of experiments on the friction prolonged to 5 or 6 days by besmearing the sur

of the axis of pallies, Coulomb obtained the folfaces with tallow.

lowing results :-When an iron axle moved in a 4. Frietion is in general proportional to the brass bush or bed, the friction was ; of the presforce with which the rubbing surfaces are pressed sion; but when the bush was besmeared with very together; and is, for the most part, equal to be clean tallow, the friction was only 's, when swines tween 1 and of that force. In order to prove grease was interposed, the friction amounted to the first part of this proposition, Coulomb em.

and when olive oil was employed as an unployed a large piece of wood, whose surface cva- 8.5' tained 3 square feet, and loaded it successively with 74 pounds, 874 pounds, and 2474 pounds. guent, the friction was never less than or

7. In these cases the friction was successively 1 1

When the axis was of green oak, and the bush of 2-46' 9.16' 2.21

of the force of pression; and guaiacun wood, the friction was is when tallow when a less surface and other weights were used,

was interposed ; but when the tallow was removed

so that a small quantity of grease only covered 1 1 the friction was

Similar re

the surface, the frietion was increased to the 9.362.42 2.40

When the bush was made of elm, the friction was sults were obtained in all Coulomb's experiments, in similar circumstances and which is the eveg wlien metallic surfaces were employed. The least of all. If the axis be made of box, and the second part of the proposition has also been esta- bosh of guaiacam wood, the friction was # and to blished by Coulomb. He found that the greatest circomstances being the same as before. If the friction is engendered when oak moves upon pine, axle be of boxwood, and the bush of elm, the fric

1 and that it amounts to of the force of prés- and the bush of elm, the friction will be it of the

tion will be and sh; and if the axle be of iron 1.78 sion; on the contrary, when iron moves upon force of pression. brass, the least friction is produced, and it

Having thus condered the origin, the nature, amounts to of the force of pression.

and the effects of friction, we shall no attend to 3. Friction is in general not increased by aug. the method of lessening the resistance which it menting the rubbing surfaces. When a super- opposes to machinery. The mostefficacious morte ficies of S feet square was employed, the friction, of accomplishing this, is to convert that spe

cies of friction which arises from one body being with different weights, was at a medium; but dragced over another, into that which is occasioned

2.28
by one body rolling upon another. As this will al-

1

1

1

1

1

« PreviousContinue »