"You will find some gored skirts during the first half of the 1860s, but they are not nearly as common as skirts cut from full widths of the fabric. They are also vastly different from the gored skirts worn later in the century:
-Â The angle of the gore is relatively shallow. The skirt is not completely smooth where it is attached at the waistline; there is still sufficient fabric at the waistline for pleats.
-Â When gored skirts first appear, only one side of each panel (the side closest to the center back) is gored. The edge toward the center front is still on the straight grain. This creates a "swept back" look to the skirt.
-Â Initially, only the side panels on the skirt were cut with the back edges gored. The center front and back panels were still full width. The style then evolved with the center front panel gored on both edges, the side panels gored on the back edges only, and the center back panel still full width. The next evolution changed the center back panel from full width to one gored on each edge. And finally, all the panels in the skirt were gored or angled on both edges. With each evolution, the width of the panels at the top got progressively narrower.
As the styles changed, it was quite common to re-work a skirt from straight panels to gores by altering the location of the side seams. On some dresses, the 'flap' of fabric created by switching to an angled seam is still hanging inside the skirt. On others the extra fabric has been cut away. In the 1870s and 1880s bodices made with the skirt fabric in combination with other fabrics became fashionable. I've examined a number of original dresses from that period that still have their 1860s bodice intact, and have used some of those skirt "flaps" in combination with other fabrics to create a new, updated bodice. I suspect this may be what happened to Bevin's mother's dress. And gored plaids were very popular, and can be very interesting when done well."
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From The Lady's Friend 1864 - Gored and braided dress; the front breadth to be cut straight, all the others gored, and formed by dividing a length of the material into two parts, cutting it in a slanted direction.