496 Proceedings of Royal Society of Edinburgh. [sess. 
the whole length of thread may be moved across the field of view 
of the microscope by the rack and pinion underneath the stage. 
The following tables show the results of micro-measurements 
on three representative yarns selected from a large collection, the 
general tendency of which is to confirm the theory discussed in 
this paper. The numbers are in micrometer divisions, each of 
which = -00618 inch. But as the subject is only relative, i.c. 
the comparison of a twist thread with a single thread, it is 
unnecessary to translate the readings into absolute measure. The 
three yarns selected are, (1) a 2/36s worsted with 16 turns per 
inch, (2) a 50-cut 2-ply woollen yarn with 9 turns per inch, (3) 
a 2/20s cotton with 9 turns per inch. 
(1) 2/36s 
I 
Worsted. 
(2) 50-cut 2-ply Woollen. 
(3) 2/20s Cotton. 
Minimum 
Maximum 
Minimum 
Maximum 
Minimum 
Maximum 
width of 
width of 
width of 
width of 
width of 
width of 
Projection. 
Projection. 
Projection. 
Projection. 
Projection. 
Projection. 
1-72 
2-32 
1-98 
2-92 
1-54 
2-51 
1-87 
2-48 
2-12 
3-02 
1-88 
2*68 
2-00 
2-35 
2'08 
3-10 
2-05 
2-68 
2-05 
2-47 
2*15 
3-25 
2-00 
2-60 
1-81 
2*20 
2-20 
3*35 
1-95 
2*55 
1-80 
2-24 
2-15 
3-30 
1-72 
2 50 
1*59 
2-32 
2-10 
325 
1-85 
2-55 
1-65 
2-45 
2*10 
3-25 
1 82 
2-55 
1-61 
2-10 
2'15 
3-25 
1-72 
2-50 
1*64 
2*05 
2-13 
315 
1-65 
2-50 
lo)l774 
10^22-98 
lo)21-16 
lo)31-84 
00 
1— 1 
00 
^ 0 ^ 
lo)25 62 
1-77 
2-30 
2-12 
3-18 
1-82 
2-56 
average 
average 
average 
average 
average 
average 
