AMERICAN INSTITUTE. 



1*79 



the "hoot completes its full revolution and enters the next loop, in 

 the process of enlarging which, it draws up the loop already formed. 

 36, the loop check employed, is a small piece of leather, or an 

 equivalent, held in contact with the periphery of the hook, so that 

 the loop cannot pass until the chamfered part h of the hook reaches 

 and frees It, as it does just as the hook enters the next loop, as 

 represented in fig. 2. Tliis rotating hook is of singularly inge- 

 nious, simple and novel construction, and is equivalent to several 

 pieces of elaborate machinery. It performs the three operations of 

 enlarging the loop of the upper thread, passing it around the bob- 

 bin, carrying the lower thread and tightening the preceding loop. 



The bobbin, 15, is placed in its proper position, with the thread 

 Sowing from the top towards the front of the machine, in which 

 direction it revolves slowly. The thread is wound upon this 

 bobbin with great facility, at the rate of one hundred yards per 

 minute. For this purpose it is placed upon the spooling spindle, 

 9, and the spool of thread upon the spool pin, 37; the thread is 

 then re-wound upon the bobbin by working the treadles, as in 

 •sewing. The upper thread may be used from the original spool, 

 38, or from another spool on which it has been re-wound. 



The tension of the two threads used, is a point of importance. 

 To form the lock stitch perfectly, the point of interlocking the two 

 threads, should be drawn to the centre of the fabric sewed, so 

 that each thread may be held firmly, and the seam present the 

 same appearance upon both sides of the fabric, a single line ot 

 thread extending from stitch to stitch. The tension of the lower 

 thread is rendered sufficiently great by tlie friction between the 

 surface of the bobbin, 15, and the rotating hook, in the cavity of 

 which it is placed, the two revolving in opposite directions. Tho 

 tension of the upper thread must be so adjusted as to draw the 

 lower thread into the fabric in the formation of a stitch. Were 

 the spools of thread always uniform, and the thread uniformly 

 wound upon them, there would be no difficulty in using the 

 thread directly from the original spool. But this is not tlie case. 

 In fig. 7 it is shown as fed from the original spool, 38, through 

 the thread guide, 39, to the tension pulley, 40, and thence through 

 the eyelets, 33, 33, to the needle, 35. The tension is attained bj 

 he volute spring, 41, pressing upon the pulley, 40, which maj 



