Just to correct some confusion about Ashley's "adjustable hitches", the name Midshipman's Hitch is actually a mistake in diagram #62. What he has pictured there is what he later calls An Adjustable Hitch [#157, 431, 1730, 1800, 1856]. In the United States scouting community, this knot is called a Taut-Line Hitch. He applies the name Midshipman's Hitch to a slightly different knot later [#1027, 1729, 1799, 1855, 1993]. Diagram 1993 has the best explanation about where the name comes from. While you are looking at these, you should also look at [#1857], which Ashley calls Another Adjustable Hitch (and he hints at this in the discussion 1800). Further there is the Adjustable Jam Hitch [#1230, 1727, 1994]. Notice that the Taut-Line Hitch and the Adjustable Jam Hitch both have a Rolling Hitch (1) [#1734] tied around the standing part but in different directions. The Midshipman's Hitch has a Rolling Hitch (2) [#1735] tied around the standing part. Finally, the Another Adjustable Hitch has what most now call a Rolling Hitch (3) {or Magnus Hitch) [1466, 1756] tied around the standing part.
See also [#215, 452, 480, 481] for possible enhancements for a Rolling Hitch. Thus, for modern slick ropes, you might want to try some of these extra wraps in any of Ashley's adjustable hitches.