Dia. IX is made to illustrate the changes of the shoulders from the
normal to the long or short neck. For this purpose the shoulders on each
back and front are made equally high, and the coat armhole connected
evenly all around. This diagram being on the square of 17½ would require
a coat to lap 2 seams somewhere. The diagram itself shows a vest on the
angle of 15 deg. and in a square of 17½, with a gore under the arm of
3¼. But the main object of Dia. IX is to illustrate the height of the
shoulders; and extra length or extra shortness of the shoulder must be
produced as shown by dots, and is further explained in the articles on
“Long Necks” and “Square Shoulders.”
This diagram also shows a shoulder slope of 30 deg., for the reason that
the base is on the front plumb line and not on the center of the front.
The front plumb line is 15 deg. back of the center, hence from it each
front and back shoulder slope is 7½ deg. out of its normal position.
If the diagram were made on the square of 20, the armhole could not be
connected all around, as it must be on the body. This diagram represents
a complete armhole, after the under arm seam is sewed, and the coat is
built around it.
[Illustration: _Dia. IX._]