number of farms in Germany which use steam ploughs, namely from 836 in 1882 to 2995 in 1907, shows that the need of mechanical aid in the tillage of the soil has steadily increased and that at the same time the machine industry has satisfactorily met the demands made upon it. But the figures given for 1907 are exceedingly small in comparison with the total number of farms. In fact they represent only a little over 10 per cent. of the farms covering upwards of 250 acres. All the other farms had to plough their land in that year and the three following years with teams, because the electric outfits that were used in some few farms might have been counted on the fingers of one hand.

At the same time the want of a cheap, mobile, mechanical plough, suited to small farms and to the shallow tillage of light soils, was all the more keenly felt as the conditions of labour grew worse and the advantages of careful tillage were more universally recognized. The hope that the use of oil engines would soon solve the difficulty, which the cumbersome steam engine could not, seemed at first impossible to be realized, and several eminent engineers considered the problem of motoculture as an insoluble one. But the laborious and expensive experiments of Robert Stock, a man who had much practice in mechanical technique and who had learned, on an estate he had then bought, to appreciate the difficulties of tilling the soil, resulted in a practical solution of the problem. In the spring of 1910 he was in a position to put before the public the first motor plough.

With a few unimportant modifications, several hundreds of Stock's motor ploughs are now used and, under suitable conditions, work satisfactorily. These ploughs weigh between 4 and 41⁄2 tons. They are so constructed that almost the whole of their weight is carried by the driving wheels, thus producing the necessary friction between the wheels and the ground. The wheels are 7 ft. 4 in. in diameter and only 6 1⁄2 inches wide ; they are furnished with lugs which project on both sides about 4 inches beyond the tyres of the wheels, so as to allow sticky soil to fall of easily. These lugs are not arranged transversely, but somewhat inclined, so that they penetrate into the soil obliquely, thus ensuring against skidding and facilitating their coming out of the ground. In order to utilize to the greatest extent the weight of the machine on the driving wheels, the fourcylinder benzine motor is situated well in front so as to counterbalance the plough shares with their frame placed at the back. The steering wheel at the tail of the machine bears thus a very small part of the weight.

Stock's plough met with great success for its several good points. It is simple in construction, for the motor and the implement form a single and indivisible whole. Nor is its working less simple. The driver sits in a light seat, with the steering wheel, the crank for regulating the depth of the shares, and the levers for driving the motor close to his hands; by means of one foot lever the motor is thrown into gear and by another one the regulator of the depth is disconnected. The machine is further simplified by there being no device for reversing or for changing its gear when once started at a certain pace. This simplicity, however, is attained at the expense of

some advantages. The change in speed can only be obtained by changing the gearing, which can only be done when the machine is not working, and besides requires a certain amount of time.

A test of Stock's plough made by the writer in 1911, on behalf of the Colonial Committee, gave the following results as to work done and consumption of fuel (1). On a mild loamy sand the motor plough worked nearly 1.73 acres in one hour to a depth of 6 1/2 inches. The field was 700 yards long and of a convenient shape. Another day 1.48 acres per hour were ploughed to a depth of 8 3/4 inches. Lastly, in consequence of several stoppages due to the field not being sufficiently dry, only 0.99 acre was ploughed per hour to a depth of 74 inches. The consumption of benzire was under the favourable conditions of the first day only 12.3 lbs. per acre, but on an average in practice it ranges from 14.3 to 19.6 lbs. per acre. The power developed, as registered by a brake dynamometer, was 33.9 H. P.

The technical success of this machine was a stimulus to other inventors to similar attempts and to further improvements. Most of them considered the want of the means of charging the speed, and especially of reversing, as disadvantages, and it must be recognized that this is true. On quite level and uniform ground a change of speed is not necessary, but when slight undulations or depressions are to be traversed it is a drawback to have to keep up the same slow pace that bas to be taken for going up hill according to the power of the motor. Still more important is reversing, for as soon as the plough is brought up by a big stone, or through a slight error of the driver by any other obstacle, the machine generally requires the assistence of horses to shift it; while if it could back it could easily disengage itself. Recently, the firm Stock has been providing its ploughs with reversing gear if demanded.

Since 1910 a number of motor ploughs have been invented, but only a few of them have survived, and deserve to be mentioned. Very similar to the Stock plough is the Wandeler-Dohrn plough of the German Motor Plough Co. (Deutsche Kraftpflug Gesellschaft); but it has reversing gear and two speeds, and its management has been cleverly simplified. The shares are fastened to a special frame which can be easily lifted and lowered, being fitted into a main frame.

The machine of the Gast Motor-plough-building Co., Ltd. (Gast Motorpflugbau G. m. b. H.) in Berlin (2) is very light. Both the tractor and the ploughing outfit are mounted on spring frames. The tractor weighs only about 2 1/4 tons. The Gast plough has reversing gear and various speeds ranging from 2.8 to 5.3 miles per hour. The separation between the motor and the ploughs which has been made in this machine has been followed by most builders. It facilitates the use of harrows, mowers, root lifters and similar machines, and is absolutely required by many farmers. At the

(1) Verhandlungen der Kolonialteehnischen Kommission des Kolonial- Wirtschaftlichen Komitees, 1911, No. 1, p. 41 et seq., No. 2, p. 62 et seq.

(2) Since the above was written the Gast Co. has been wound up. (Author's note).