Absolutely typical of the light, treadle-driven lathes made for amateur use from around 1850 to 1920, the F. Pratt & Co. 3.5" x 21" lathe shown above has survived in remarkably fine original condition - even to the wooden tool tray at the back of the stand and treadle foot-board.
Similar to the type produced in much greater numbers in the UK by Britannia as their models No. 2 and No. 3,  the Pratt version was unusual for an English design in having (instead of a flat bed) a flat and V to locate headstock, hand-rest base and tailstock. The headstock, lacking a speed-reducing backgear, was of the simplest possible design having just a single plain bronze bearing at the front to support the solid spindle with its rear held against an adjustable hardened point. This arrangement, despite its many potential shortcomings, was inexpensive to engineer, effective in practice and a design that many makers persisted in using until the 1920s. The 4-step headstock pulley was not intended to be driven by a V belt - it would be a long tine before they appeared - but a round leather "rope", "gut band" or "cord" as it was variously called, a type that severely limited the amount of power able to be transmitted. The rather light flywheel (owners often bolted weights to them) was equipped with three grooves near its periphery to provide slower speeds and two on the inside to give higher. As the spindle pulley was not wide enough to span the grooves in the flywheel, it was necessary to slacken the single bolt holding the headstock down and reposition it on the bed to get the belt in line - though in practice the latter's very thinness enabled it to tolerate a considerable degree of misalignment.
Although intended for wood turning, it is likely that Pratt would also have offered a compound slide rest for light-duty metal work..

Backgeared and screwcutting Pratt lathe from circa 1890-1910. With a centre height of around 7 inches and a between-centres capacity approaching 7 feet this would have been one of the Company's larger models. This lathe was found in semi derelict condition and has been restored to full working order driven by a proper, wall-mounted countershaft system. Fortunately the lathe came complete with its originl very large set of screwcutting changewheels, steadies, chucks and faceplates. Note the huge detachable gap in the bed and (shown in the picture below when the lathe was found) a shaft to drive the power cross feed running along the back of the bed - a Victorian-era design used by many manufactures with examples shown here: a larger Spencer lathes, Pools Major, Mellor, Jones & Burton and Portass

With only carbon-steel cutting tools available, the need for a massively built lathe was not such a great concern - hence the relatively skinny  proportions of this example

Tailstock: like the headstock this had a taper of an unknown type in both ends of the spindle - two dead centres that fitted being found with the lathe, together with adapter from the unknown taper to MT3

Recently discovered (2021) this Pratt lathe is smaller and slightly younger than the restored long-bed model newer and has a few points of interest: For its centre height it's rather long and able to take around 5 feet between centres; drive came, originally from a foot treadle, the bearings still being present in the legs; unlike the restored example, there is no rear-mounted power shaft, instead power to drive the cross slide is provided by worm-and-wheel gearing inside the apron, the leadscrew, of course, acting the worm; the spindle bore is 1", large for the era on this size of machine. Presently in storage, it will eventually be set up alongside the larger Pratt.