FREYBURG FRICTION. 



323 



has been worked for two centuries uninterruptedly, 

 and yields annually about 70,000 dollars worth of 

 silver. It afforded, from 1769 to 1818, 2176 cwt. of 

 silver. Among the establishments in the neighbour- 

 hood of Freyberg, are the large silver furnaces, and 

 particularly the amalgamating works, where 60,000 

 cwt. of ore is melted annually. According to Brei- 

 thaupt's Die Alte und freie Bergstadt Freiberg in 

 Hinsicht ihrer Geschichte, Statistik, Cultur und 

 Gewerbe (Freyberg. 1825), the mines of this city 

 have produced 240 millions of Saxon dollars, or 

 80,000 cwt. fine silver, in 640 years. 



FREYBURG ; formerly capital of the Brisgan, 

 now the chief place of the circle of the Treisam, in 

 the grand duchy of Baden, to which the Brisgau was 

 ceded by Austria, at the peace of Presburg (1805.) 

 Freyburg is situated in a romantic district in the 

 Black Forest; population, 10,000. Its minster, the 

 Gothic steeple of which is 513 feet high, and is one 

 of the few Gothic steeples which is complete, is a 

 magnificent edifice. Vater has published lithora- 



hic views of it (Freyburg, 1826), and Schreiber 

 escribed it (Freyburg, 1820.) The university, 

 which has some men of distinction among its profes- 

 sors, and in which the number of students increases, 

 was established in 1746. It is highly creditable to 

 so small a country as Baden, which contains also the 

 celebrated university of Heidelberg. The vicinity 

 of Tubingen is of some disadvantage to it, yet, in 

 1 825, it had 600 students. Freyburg has likewise 

 a forest academy and a polytechnic school. 



FRIBURG ; a canton of Switzerland, surrounded 

 by the cantons of Berne and Vaud, except a narrow 

 part, which touches the lake of'Neufchatel. The 

 north-west part of the country is more level than the 

 rest, and produces abundance of corn and fruit ; the 

 other parts are mountainous, but contain good pas- 

 tures, which feed great herds of cattle. The chief 

 exports are cattle, outter, and particularly the excel- 

 lent cheese known by the name of Gruyere. Square 

 miles, 795 ; population, 67,874 ; 7300 Protestants, 

 the rest Catholics. 



FRIBURG OB FREIBURG; called Frilurg in 

 Uchland. to distinguish it from Friburg in the Bris- 

 gau ; a town in Switzerland, capital of a canton of 

 the same name, sixteen miles S. W. of Berne, 

 twenty-seven N. E. of Lausanne ; Ion. 6 48' E. ; 

 lat. 46 50' N. ; population, 6461. It contains four 

 churches, eight convents, three hospitals, and a col- 

 lege, with fifteen professors. It is situated on the 

 Sanen, and almost surrounded by it. Part of it is 

 built on an elevated rock, part of it in a deep valley, 

 and towards the west it occupies a small plain. The 

 streets are irregular, steep, clean, and tolerably wide ; 

 the houses are well built, and some of them hand- 

 some. It is surrounded with walls, towers, and sharp 

 rocks. The small river which divides the town also 

 makes the boundary between the German and French 

 languages ; and it is curious to see the population of 

 one city, who have lived for centuries together, still 

 distinguished in language, customs, and manners. 



FRICTION; the act of rubbing two bodies 

 together, or the resistance in machines caused by the 

 motion of the different parts against each other. 

 Friction arises from the roughness of the surface of 

 the body moved on, and that of the moving body ; 

 for, such surfaces consisting alternately of small emi- 

 nences and cavities, these act against each other, and 

 prevent the free motion that would ensue on a supposi- 

 tion of the two bodies being perfectly polished planes. 



Mr Ferguson found that the quantity of friction 

 was always proportional to the weight of the rubbing 

 body, and not to the quantity of surface ; and that 

 it increased with an increase of velocity, but was not 

 proportional to the augmentation of celerity. He 



found also, that the friction of smooth soft wood, 

 moving upon smooth soft wood, was equal to one- 

 third of the weight ; of rough wood upon rough 

 wood, one-half of the weight ; of soft wood upon 

 hard, or hard upon soft, one-fifth of the weight ; of 

 polished steel upon polished steel or pewter, one- 

 quarter of the weight ; of polished steel upon cop- 

 per, one-fifth ; and of polished steel upon brass, one 

 sixth of the weight. 



Coulomb made numerous experiments upon friction, 

 and, by employing large bodies and ponderous 

 weights, and conducting his experiments on a large 

 scale, corrected several errors, which necessarily 

 arose from the limited experiments of preceding wri- 

 ters. He brought to light many new and striking phe- 

 nomena, and confirmed others, which were previously 

 but partially established. We cannot, in a work of this 

 kind, follow M. Coulomb through his numerous and 

 varied experiments ; all that can be expected will be 

 a short abstract of the most interesting of his results ; 

 a few of which are as follows : 1. The friction of 

 homogeneous bodies, or bodies of the same kind, 

 moving upon each other, is generally supposed to be 

 greater than that of heterogeneous bodies ; but Cou- 

 lomb showed that there are exceptions to this rule. 

 2. It was generally supposed that, in the case of 

 wood, the friction is greatest when the bodies are 

 drawn contrary to the course of their fibres ; but 

 Coulomb showed that the friction in this case is some- 

 times the smallest. 3. The longer the rubbing sur- 

 faces remain in contact, the greater is their friction. 

 4. Friction is, in general, proportional to the force 

 with which the rubbing surfaces are pressed together, 

 and is commonly equal to between one half and one 

 quarter of that force. 5. Friction is not generally 

 increased by augmenting the rubbing surfaces. 6. 

 Friction is not increased by an increase of velocity : 

 at least it is not generally so ; and, in some cas-s, 

 even decreases with an increase of celerity. 

 7. The friction of cylinders, rolling upon a hori- 

 zontal plane, is in the direct ratio of their weights, 

 and in the inverse ratio of their diameters. 



An easy method of experimenting on the friction 

 of surfaces, is, to place a plank with its upper sur 

 face level, and on this a thin block of the matter to 

 be tried, with a cord fixed to it, which block may be 

 loaded with different weights ; and a spring steel- 

 yard attached to the other end of the cord, to draw 

 it along by, will show the force necessary to produce 

 motion. It appears from experiments, that the fric- 

 tion of different combinations of matter differs very 

 considerably, and that an immense quantity of power 

 may be lost in a machine by using those substances 

 for the rubbing parts which have great friction. In 

 a combination where gun-metal moves against steel, 

 the same weight may be moved with a force of 15^ 

 pounds, which it would require 22 pounds to move 

 when cast iron moves against steel. 



The resistance called friction performs important 

 offices in nature and in works of art. Friction 

 destroys, but never generates motion. Were there 

 no friction, all bodies on the surface of the earth 

 would be clashing against one another ; rivers would 

 dash with unbounded velocity, and we should see 

 little besides collision and motion. At present, 

 whenever a body acquires a great velocity, it soon 

 loses it by friction against the surface of the earth ; 

 the friction of water against the surfaces it runs over 

 soon reduces the rapid torrent to a gentle stream ; 

 the fury of the tempest is lessened by the frictioo of 

 the air on the face of the earth ; and the violence of 

 the ocean is subdued by the attrition of its own waters. 



Its offices in works of art are equally im- 

 portant. Our garments owe their strength to fric- 

 tion ; and the strength of ropes, sails, and various 

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