William Carpenter's The Angler's Assistant was an important, if often overlooked, early Victorian fishing treatise. Published in 1848, it gave a classic definition of the art of trolling, which is reproduced here:
Anglers divide trolling into three kinds: sinking and roving with live bait—trolling with gorge and snap hooks, and dead bait—and spinning, in which the fish with which the hook is baited, whether real or artificial, is given a revolving motion.
The fish to be taken by trolling are salmon, trout, pike, and perch.
Trolling is much esteemed, especially in the vicinity of London, and is practised when other modes of fishing are useless.
For trolling, properly so called—that is, with a gorge bait—the rod should be long and stout. A wellseasoned bamboo-cane, from fourteen to sixteen feet in length, is the best you can have; but in the absence of this, take the next best within reach. If you have a winch on the rod, there should be a ring on each of its joints; but if a thumb-winder is used, which some prefer, a large ring at the top of the rod, or at most two or three up it, will be ample. The rings must be large and strong, however, and the top one, two or three times the size of the rest. Trolling is sometimes practised, and not unsuccessfully, with a hedge stick, having a forked top, the line passing from the thumb-winder over the fork of the stick, which thus forms the top of the rod.
The trolling-line should be of silk, or of silk and hair; the former, however, is preferable. The length should be from fifty to sixty yards, and it should be seasoned, or dressed, by being put through cold-drawn linseed-oil, and then drawn through a piece of flannel or woollen cloth, held in the hand, after which it should be hung up for a few days in the air. The bottom line should be made of fine gimp, if for pike; or of the best gut, if for trout, about a yard and a half long, with a box swivel attached to it, about a yard distant from the hook, so that the bait may turn freely.
The gorge hook for a pike is formed of two single eel hooks, fastened back to back, to two or three inches of twisted brass wire, the end of which is formed into a loop, to be attached to the gimp or gut line, before described. Instead of using shot, as in other cases, the shank of the hook and part of the twisted wire are to be neatly covered with lead, taking care that it does not pass so far over the hook as that the jack, if he put his teeth through the bait-fish, will come in contact with the lead, as this would probably induce him to drop the bait and be off.
-- Dr. Todd