869 



CATGUT STRINGS. 



CATHARTICS. 



670 



abscissa is A N or x, and its ordinats N p or y. Let the length of the 

 arc A P be s, and the angle N T P be 9. Let Aa be made equal to t inches, 

 and through a draw a horizontal line a p. Hence if c A were taken away, 



and the chain suffered to hang over a fixed point at A down to a, the 

 part D A would not alter its form. And it ia the most striking property 

 of the curve, that if the portion D p above any point p were taken away, 

 and the chain suffered to hang over a fixed point at p down to the same 

 horizontal line a p, the part CAP would be maintained by the portion 

 p p in its position. 



The following are the equations which connect T t, x, y, s, and 9 : 



where e=base hyp. log. = 27182818 . . . 



Given the distance between c and D = 2e, and the length of the 

 whole chain CAD =2i, then the value of 9 at the point D, supposing a 

 tangent drawn there, must be found by approximating to a solution (fl 

 being unknown) of 



c 8 



j = tan. 8 hyp. log. cot. - 



which might be solved by inspection, if a sufficient table of the values 

 of the second side were formed. The extreme value of S being thus 

 found, which call A, t is found from ( = I tan. A, and thence the tension 

 at any point of the curve can be found ; and A B, which call h, is found 

 from h= V P-tP t. The preceding equation may be thus adapted 

 to the common logarithms, 



x '4342945 =tan. 0. com. log. cot. - 



i 2t 



But in practice it would be sufficient to hang up a thin metal chain 

 against two points in a vertical board, in such manner that c D and 

 CAD should represent the lengths required on any convenient scale. 

 Then A N and A P should be measured for several different points, and 



(AP) J - (AN) 



\ should be found for each. 

 \* "/ 



If the catenary were perfect, these should all give the same result, 

 namely, the required value of t ; but as this will not be found to be 

 the case, a mean of the values should be taken. 



When AB is small compared with c D, \ mustjbe nearly a right angle, 

 and t is very great. The catenary in that case is very nearly a part of a 

 parabola, which it wag supposed to be altogether by Galileo. The 

 focal distance of that parabola is the half of t. We have seen people 

 puzzled to know how a horse on a towing-path draws a heavy boat by 

 a rope which appears slack, and even dips into the water. The reason 

 is, that the tension necessary to pull a long rope into anything like a 

 straight line, is much greater than that which is necessary to move the 

 boat. A full geometrical account of the catenary, with tables, is given 

 in Ware's ' Tracts on Vaults and Bridges.' 



CATGUT STRINGS. Several useful articles, manufactured from 

 the intestines of the sheep, are, for some unexplained reason, denomi- 

 nated catgut. The catgut is generally in the form of cord, string, or 

 twine. The chief purposes to which such cord is applied, are musical 

 string* for harps, violins, and guitars ; hatters' bowstrings, for the 

 bowing or disentangling of fur and wool; clockmakers' cord ; and thongs 

 or cords for whips for all of which purposes the material requires a 

 careful preparation before being brought into the state of cord. 



The intestines, when taken from the animal, are, by repeated washing 

 and scraping, freed from the loose adherent matters; and are further 

 steeped for some time, as a means of loosening the surface membranes. 

 When this steeping has brought them to a particular state or stage, 

 they are laid on a sloping board, and scraped with the back of a knife, 

 in such a manner as to peel off two strips of peritoneal or external 

 membrane, each equal in width to half the circumference of the intes- 

 tine. The membrane so removed is called by the French filondre, and 



is employed by them, when further prepared, for making the cords for 

 rackets and battledores, and also as thread for sewing pieces of intes- 

 tine together for other purposes. When the membrane is removed, 

 the intestine is again steeped in water, and the inner or mucous mem- 

 brane scraped from it ; and it is also exposed to the action of an alkaline 

 ley, until at length it is brought to as clean a state as possible. The 

 large ends are cut off and applied to other purposes ; the smaller ends 

 are laid by for making cord. 



In the making of violin-strings, after a process of cleaning, the 

 intestines have a certain degree of twist imparted to them. Two or 

 more are affixed, at the ends, to a rotating machine, and twisted round 

 each other somewhat in the same way as twine or silk. The size of 

 the membranes, and the number of them twisted together, depend on 

 the thickness of the string to be made. The twisted strings are ex- 

 posed to the action of sulphur in a closed chamber, and are then rubbed 

 with a horsehair cloth ; these processes are repeated two or three times. 

 If a string be sulphured too much, it becomes too brittle ; if too little, 

 it rarely keeps in tune; the determination of the proper degree of 

 sulphuring becomes therefore a nice point in the manufacture. 



The Italians have generally the reputation of making better violin- 

 strings than any other people. The violinists of England, France, and 

 Germany acknowledge the fact, but without being able to assign a 

 sufficient reason for it. The late Dr. Ure suggested the following 

 considerations : It is well known to physiologists that the membranes 

 of lean animals are far more tough than of those animals which are fat 

 or in high condition. In London, where the sheep slaughtered are 

 mostly fat and high-conditioned, the membranes of the animal are 

 supposed to be less tough and tenacious than those of Italy, which are 

 not so highly fed ; hence it is inferred that the membrane employed 

 by the Italians is better fitted for the manufacture than that used by 

 the English manufacturers. Whether this be so or not, the fact of 

 the pre-eminence is admitted. Otto, in his ' Treatise on the Violin,' 

 (translated from the German by Mr. Fardely), says in relation to violin 

 strings : " The best strings which have come under my observation 

 are those from Milan, which are sold under the name of Roman strings ; 

 they are now to be had at almost every music shop. I shall point out 

 the signs by which the best strings may be distinguished ; as there 

 are some imitations of them manufactured at Neukirch, in Voigtland, 

 in Bohemia, and in the Tyrol, which are sold for Italian. The Milanese 

 strings are as clear and transparent as glass. The third string should 

 be equally clear as the first. They must by no means feel smooth to 

 the touch, for they are not ground or polished off by any process, as 

 all other manufactured strings are. If a good string be held by one 

 end in the finger, and opened out, it will recoil to its former position 

 like a watch spring. Every string, when stretched on the instrument, 

 should look like a thin strip of glass on the finger-board : those which 

 are of a dull and opaque appearance are useless. The Milanese strings 

 are also distinguished by each separate one being tied twice with red 

 silk ; which however the Neukirch string-makers have imitated. Their 

 elasticity is after all the best criterion ; as no other strings which I 

 have tried have that strength and elasticity for which the Milanese are 

 so much esteemed." 



The thickest string of the violin, and many other musical strings, 

 are coated with an envelope of fine wire. This is done by stretching 

 the string very tightly, applying the wire at one end of it, and causing 

 the wire to coil helically round the string by giving it a rotatory 

 motion. 



For the strong thick cord used for hatters' bowstrings, the largest of 

 the membranes are used, after being cleansed and prepared ; from four 

 to twelve of them being twisted together, according to the size of the 

 cord to be produced. The pieces are twisted to a length of fifteen, 

 twenty, or twenty-five feet ; and to effect this, pieces of the membrane 

 are sewed end to end, till they produce the required length. While 

 under the process of twisting, the cord is well rubbed between the 

 fingers, to equalise the thickness. The cord is exposed twice to the 

 fumes of sulphur, and is rubbed repeatedly afterwards. 



The catgut employed by clockmakers is prepared from the smaller 

 intestines, well prepared with potash. The hollow membranous tube 

 is sometimes cut into two strips in a curious way. The tube is drawn 

 over a ball, behind which is a kind of knife having two cutting edges 

 or blades, whereby the tube is ripped up into two oblong strips of 

 equal width. The method somewhat resembles that by which straws 

 are split for the straw-plait manufacture. For larger and stronger 

 purposes, clockmakers sometimes use cord composed of two or more 

 intestines twisted together, as for violin-strings. The catgut for whips 

 and similar purposes is prepared and wrought much in the same way ; 

 short pieces being sewed together to produce a piece of the requisite 

 length, and this being twisted to give it a sufficient degree of strength. 

 The bands or cords for turning-lathes used generally to be formed of 

 coarse horse-gut ; but these are now mostly superseded by India- 

 rubber bands. 



For the mode of preparing, from a membrane covering the intestine 

 of the ox, the fine pellicle known by the name of " gold-beaters' skin," 

 see GOLD-BEATINO. 



CATHARTICS are material agents which cause a transient but 

 special irritation of the intestinal canal, followed by alvine dejections. 

 It is not necessary that these substances should be placed in direct or 

 immediate contact with the mucous membrane of the intestines, either 



