[ 175 ] 162 



but as the filament of the silkworm is of extreme tenuity, it is neces- 

 sary, in the winding, to conjoin the filaments of fi-om five to seven co- 

 coons, in order to obtain a single thread of the requisite stajjle. The 

 raw silk, thus composed, is still, however, too slender far the purposes 

 of manufacture; and accordingly, the first process which it undergoes, 

 is that of uniting two, three, or four threads into one, previously to 

 giving it that kind of twist which is technically termed organzining. 



The machine by which the union of the required number of threads 

 is effected, is denominated a tramming engine, and admits of a considera- 

 ble variety of structure: but the conditions absolutely essential in all, 

 are the following: first, that the silk may pass oft' easily, and vyithout- 

 entangling, from the delivering bobbins: secondl}-, that a small and 

 equal degree of tension be applied to the threads as they pass from the 

 delivering bobbins, to the receiving one, so that the compound threads 

 shall be perfectly even ; which obviously would not be the case, if one 

 of the component threads were quite loose, while the others were drawn 

 straight; thirdly, that the receiving bobbin ceases to revolve as soon as 

 any one of the component threads happens to break — an accident which 

 not unfrequently occurs; as, without such contrivance, a thread would 

 be produced of variable thickness, from the casual omission of one or 

 more of the component threads. 



The operation of tramming, in some of the best constructed mills, i? 

 performed in the following manner: 



The delivering bobbins (varying in number from two to four, accord- 

 ing to the intended thickness of the component thread) are placed upon 

 as many vertical spindles, the vertical position allowing the threads to 

 quit the bobbins without any motion or revolution of the bobbins them- 

 selves. Some way above the bobbins, the threads pass singly betweeir 

 two horizontal slips of cloth or felt, which, by their friction, give at 

 the same time a certain degree of tension to the threads, and clear them 

 from any dust or other light matter. Each thread then passes through 

 the eye of its own drop-wire, whence they all converge and unite in 

 the eye of the guider, from which the compound thread is distributed 

 on the surface of the receiving bobbin as it revolves. Each drop-wire 

 consists of a piece of wire turned up, so as to form a light angle, of 

 Vi^hich the vertical leg is about two inches long, and is terminated by 

 an eye through which the thread passes; and the horizontal leg. is about 

 four inches long, terminating likewise in an eye, through which passes 

 a pin, connecting all the four drop-wires, and forming a pivot, on which 

 each is capable of moving freely. Eacli thread, in passing through 

 the eye of its drop-wire, slips down a little, and, being in a state of mode- 

 rate tension, supports it at the elevation of half an inch or more above 

 the position to which it would otherwise descend. When, therefore, 

 a thread breaks, its drop-wire immediately falls, and strikes on the 

 edge of a wire-frame, moving on a horizontal pivot, and so adjusted 

 that the weight of the drop-wire immediately inclines downwards that 

 side which it touches, and consequently raises the opposite side. To 

 this opposite side a tail of wire is attached, which, wdien raised, catches 

 <xn a kiad of ratchet-%vheel, fixed on the same spindle as the receiving 



