Engineers and Mechanics Encyclopedia 1839: Railways: Sans Pareil
The Sans Pareil of Timothy Hackworth does not materially differ from the Rocket, the most conspicuous variation being the vertical, instead of the inclined position, of the working cylinders. The boiler B is cylindrical, of the Trevithick kind, with one of its ends convex outwards, and the other flat. The fire-bars were of greater extent than usual, having an area of ten feet; and the flue-tube is returned to the front on one side of the fire-place, where it enters the chimney C. This fire-tube is of course entirely surrounded by the water in the boiler, and hence a considerable surface (though not so great as in the Rocket and Novelty) of heated metal is brought into contact with the fluid to be evaporated.
D represents one of the two working-cylinders; these were seven inches in diameter, and had an eighteen-inch stroke. The piston rods, through the medium of the vertical connecting rods, operated upon the hind pair of wheels; and the latter being connected to the fore wheels by the horizontal connecting rods, shown acting in the manner of cranks, motion was communicated to both pair of wheels, - an arrangement which is designed to cause a greater adhesion of the wheels to the rails, and of enabling the carriage to draw a greater load, than if only one pair of wheels was operated upon.