These warp threads are extended up and down, in the original mounting of the piece, between a top and bottom hori zontal roller or beam, of which one is called the warp beam, and the other the lace beam, because the warp and finished lace are wound upon them respectively. These straight warp threads receive their contortion from the tension of the weft threads twisted obliquely round them al ternately to the right and the left hand.
If we pursue the path of a weft thread, we find it goes on till it reaches the outermost or last warp thread, which it twists about ; not once, as with the others, but twice ; and then returning towards the other border, proceeds in a reverse direction. It is by this double twist, and by the return of the weft threads, that the selvage is made.
The ordinary material cf bobbin-net is two cotton yarns, of from No. 180 to No. 250, twisted into one thread • but some times strongly twisted single yarn has been used. The beauty of the fabric de pends upon the quality of the material, as well as the regularity and smallness of the meshes. The number of warp threads in a yard in breadth is from 600 to 900 ; which is equivalent to from 20 to 30 in an inch. The size of the holes cannot be exactly inferred from that circumstance, as it depends partly upon the oblique traction of the threads. The breadth of the pieces of bobbin-net varies from edgings of a quarter of an inch, to webs 12, or even 20 quarters, that is, 5 yards wide.
Bobbin-net lace is manufactured by means of very costly and complicated machines, called frames.
The bobbin of a net machine is a curi ous contrivance. The cotton is wound on to a bobbin or reel from the skeins by a winding machine, and thence trans ferred to the little apparatus of the bob bin-net machine. This apparatus is so minute that the whole of it, inclusive of the bobbin on which the cotton weft thread is wound, and the carriage or frame in which it is placed, is not thicker than the diameter of the meshes in the net to be made. This thickness is often not more than the one-thirtieth of an inch.
The bobbin consists of two thin disks of brass about an inch and a half in diame ter, laid face to face, with a slight inter veiling space ; and in this minute space the thread is wound, in quantity about fifty or sixty yards to each bobbin. The bobbin is then fitted into a kind of car riage, which conveys it between the threads of the warp, and at the same time allows the thread to be unwound from the bobbin : in short, the carriage is to the bobbin what the little boat of a shuttle is to the pin on which the weft thread is wound.
No less than three thousand six hun dred of such bobbins as are here de scribed are sometimes used in one ma chine ! Many of the machines are twenty quarters wide—that is, fitted to the manu facture of net five yards in width ; and have twenty of these bobbins to the inch.
If the arrangement of such a machine be examined, it will be seen that the warp threads are wound on a beam in the lower part of the machine, from which they as cend to the upper Wert. The warp is di vided into two parcels (somewhat in the same manner as the warp of a common loom by the action of the treadles), and each parcel is susceptible of a reciproca ting motion, alternately to the right and left. The weft-threads, wound on the bobbins, are fastened each at one end to the upper part of the machine ; and the bobbins are suspended so as to have a backward and forward motion between the warp-threads, like so many clock pendulums, being guided between the warp-threads by a very curious piece of ap paratus called a " comb." The principle of action, then, is this :—After the bob bins have been driven between the re spective warp-threads, the warp is shifted a little on one side, so that, when the bobbins return, they pass through open ings different from those which they traversed in the first instance ; and by this means the weft-thread, unwinding from•each bobbin in the course of its movement, becomes twisted around one of the warp-threads. After this has been repeated two or three times, the comb which carries the bobbins is itself shifted to and fro laterally, by which the bobbins are brought opposite to openings between the warp threads different from those to which they were before opposed. Herein lies the whole principle. According as the front layer of warp, or the hinder laver, or the comb carrying the bobbins, are shifted to and fro laterally, so does the weft-thread, as it becomes unwound from the bobbins, twist round the warp threads during the passage of the bobbins across ; a shifting, in one or other of several different ways, being effected im mediately after each traverse of the bob bin. After a certain number of twist hags have been effected, a series of points become inserted between the warp threads, and temporarily hold up the knotted twists so as to form the meshes of the net.