the Philadelphia Centennial Exhibition. 
31 
viz., the machine shown by the Scrcw-Moiver Company, and a more modern 
arrangement, known as the Reciprocating Screw-Mower, manufactured by the 
National Ironworks, New Brunswick, N.J. With regard 'to the former, it is 
sufficient to say that the gear comprises a large gun-metal screw-wheel on the 
main axle, actuating a worm on the crank-shaft. The wheel works in an oil- 
box, and this is necessary to prevent friction. The action is very direct, but 
the oil is a fatal objection; farmers are too careless for such an arrangement. 
Either the oil would be altogether neglected, or left in the receptacle to solidify 
and dry up. Moreover, when tried under the most favourable conditions, the 
draft was by no means light. The Reciprocating Screw-Moivcr has more merit, 
and is a striking departure from ordinary patterns. In this machine there is 
neither <*ear nor cog-wheel, crank nor revolving jernal, except the main axle. 
The whole weight of the machine is supported by the two driving-wheels, 
and the entire weight is made use of to give motion to the knives. The 
driving-wheels are arranged to work either together or independently of each 
other, "which allows the knives to work whilst the machine is making short 
turns, either right or left. The facilities thus secured were shown by the 
exhibitor himself, who cut out pieces of grass with ease. The power obtained 
from the forward motion of the wheel is imparted to the shaft from the rim of 
the wheels by means of arms and notched teeth on the rim of the wheel. In 
this way the knife is very directly set in motion, and this was exemplified by 
placing a piece of wood between the blades, and cutting it in two by revolving 
the wheel without the necessity of gathering power by backing. It is pro- 
bable, though the experiment was not tried, that no ordinarily geared machine 
would have done this. The notched arms can be readily thrown in and out 
of gear. It is a fore-cut machine ; the driver's seat, being placed behind the 
axle, balances the weight on the horses' necks. The cutter-bar is jointed to 
the frame ; two levers control the working of the machiue. One of them raises 
or lowers the cutter-bar, and also swings the frame and cutting-apparatus 
clear of the ground: the frame is strong, and simple in construction. The 
mechanical principle — which is that of the bolt-and-nut — was so well described 
by Mr. William E. Kelly, in a paper read before the Middlesex, U.S., Farmers' 
Club, that I reproduce a portion of his remarks. 
Figs. 23-27. — W. F. Goodwin's Reciprocating Screw-Moicer. 
Fig. 23. Fig. 24. Fig. 25. 
" The pattern is made with a cylinder of wood 8-in. diameter, which is laid 
out with 19 right and 19 left-hand threads around its circumference. These 
threads cross each other, and form 19 points of intersection ; by following 
the right and left hand threads from each of these points we get a line of 
intersection. If we should pass a plane through each line of intersection per- 
pendicular to the axis of the cylinder, we should virtually cut the cylinder 
into two pieces, and the section would present 19 corrugations or V-shaped 
grooves, and corresponding projections radiating from the centre of the points, 
where the right and left hand threads intersect. Fig. 24 shows centre or bolt 
section. A section of the nut is made in the same manner, and of course 
corresponds exactly with the section of the bolt. Fig. 25 gives exterior view 
of one of the nut sections. The section made from the bolt has a sleeve cast 
