Vol. XIII. No. 32-5. 



THE AGEICULTURAL NEWS. 



331 



STUDENTS' CORNER. 



DYNAMICS OF A PLOUGH.* 



Paut III. 



To jjeniiit tlie line of force being made a straight line to 

 the centre of resistance under all circumstances, the beam at 

 its point is fitted with a long bridle provided with pin holes 

 for lateral adjustment and moveable up and down, so that the 

 point of attachment of the team to the beam is adjustaljle in 

 practically all directions. If the forces could be applied on 

 the line AB, fig. 8, none of it would be wasted in doing use- 

 less work. As, however, it has — for the reason stated — to be 

 applied oblicjuely, as shown in fig. 9, under the principles of " 

 the parallelogram of forces, out of the total power so applied 

 only about 7-5 per cent, is applieil to overcome the resistance 

 and draw the plough horizontally forward, the other 2-5 per 

 cent, acting to lift the whole plough vtn-tically. In fig. 10 the 

 oblique force is decomposed inti^ two c(>mponents, one 

 horizontal (AB) and one vertical (AE). 



lines and as the direction of the draught is not ncjw in 

 a straight line to the centre of resistance, the plough will lift 

 behind until the bridle-pin is lowered to bring the draught- 



Fig. 11. 



line straight. If, on the otlier hand, the bridle-pin is below 

 the straight line from hanie-hook to centre, then for the same 

 reason the jjlough will be lifted in front. We have so far 

 considered only the eftect of different verticle positions of 

 draught, but the same rules apply also to the horizontal posi 

 tion, the balance-point in the plough-body being the balance- 

 point both for the vertical and horizontal planes. 



Fk;. 10. A. Centre of Resistance. 



AC. Line of Draught, the Diagonal. 



AE. CB. I'arallelcjgram of Force. 



AB. Force acting to draw l?lough forward. 



AE. Force acting to draw Plough upward. 



The magnitude of the total force being represented by 

 the length of the line AC (say -540 lb.) the m.ignitude of the 

 forces AD and AE is proportional to their length — in this 

 case 1-1 to i; the power therefore applied to draw the plough 

 forward is -120 Itj., and that to lift it vertically is 120 H). 

 It will be seen from this that, contrai-y to the ordinary 

 opinion of ploughmen, the further the horses are away from 

 the plough the less power will be required to draw it: as the 

 parallelogram of force becomes longer it becomes narrower, 

 and less of the total power is wasted in lifting the plough 

 vertically — that is, AE becomes less and AB greater the 

 further the horses are from the [ilough. It has to be noted 

 that the centre A is also the balaTice-point, and that theoreti- 

 cally, so long as the force is applied in a straight line to 

 A, no matter what the obliquity of the line may be short of 

 a right angle to the horizontal, the plough will run straight 

 forward on a level keel, the force AE acting vertically to lift 

 the plough by the balance-point, but wasting more and more 

 of the total pow-er as the angle of draught deviates 

 from the horizontal. This, however, only holds true 

 in actual practice within a small range for the vertical 

 position of di-aught, and a still smaller range for the 

 horizontal position. Should the bridle pin be placed 

 above the straight line from hame-liooks to centre of 

 resistance, as in F'ig. 11, as force acts in straight 



* The Jonnvil of Agrkultuve of New Zealand for .Turn 

 20, 1014. 



New Sources of Oil. — Dumoria Heckeli, found on 

 the Ivory Coast Ijy Chevalier, is native of tropical forests. 

 Its seeds yield a semi-solid oil, snow white when fresh, with 

 a pleasant sweet flavour and slightly aromatic, at the rate 

 of 16 '.5 per cent, of the seeds or 33'2.5 per cent, of the 

 kernels. 



BailloneWi toxisperma, Pierre, or Mimusops Djawa, 

 jilngler, has been recently found in the Mayumbe district of 

 the Belgian Congo. It yields a white aromatic oil at the 

 rate of .56'04 per cent, of the kernels or 40".50 per cent, of 

 the seeds. 



Both residual cakes are unfortunately toxic on account 

 of the presence of a glucoside of the saponin group, but 

 they may lie employed as manure, for they contain a consid- 

 erable amount of potash and nitrogen (2 and 3 per cent., 

 respectively) though very little phosphoric acid (Dumcma 

 HeckeH 0'75 per cent.). 



WEST INDIAN COTTON. 



Messrs. Wolstenholiiie and Holland, of Liverpool, 

 write as foII<5ws, under date September 19, 1 914, with 

 reference to the sales of West Indian Sea Island 

 cotton: — 



Since our last report ab(.iut 40 iiales of West Indian 

 Sea Island cotton have been sold. Tliese include 17 bales 

 St. Vincent, 22i. to 31rf., which were offered before the war; 

 the remainder being St. Kitts" cotton, 1.5d to 16c/. for Old 

 Crop, and lOW. for a few bags of New Crop. 



The fine trade continues disorganized owing to the war, 

 and we are afraid will continue to remain so, because some of 

 the chief consuming markets are in the region of Lille, where 

 the fighting is now taking place. 



The report of Messrs. Henry W. Frost & Co., on 

 Sea Island C(.)tton in the Southern States, for the week 

 ending September 12, is as follows: — 



Only one bag of the New Crop has been received so far. 

 The stock of 38 bales consists of two planters' crops brought 

 over from last season. It will be a fortnight yet before the 

 receipts are large enough to admit of our judging the quality 

 of the odd bags of the crop. The reports from the planta- 

 tions are favourable. 



