Y O L 



line, each pulls by the traces of the one behind him ; and 

 therefore, though it may be known when the foreraolt 

 negleas his work, by the (lackening of his traces, it cannot 

 be known when any of the reft negleft their work ; for 

 though one of them does this, yet by the pu Ihng of the 

 one before him his traces may be fully ftretched. But this 

 is eafily difcovered when the cattle are yoked in pairs ; tor 

 then every one of them has a feparate draught. 



There is ftill another inconvenience that attends the 

 common way of yoking cattle in a line before each other. 

 When the fore cattle are all yoked to the traces of the 

 hindmoft, it is obvious, that as the beam to which the 

 draught is fixed is much lower than his (boulders, by which 

 the reft pull, fuch a weight mull be laid upon his back or 

 (houlder, as muil render him incapable of giving any aUilt- 

 ance. Bcfidcs, as the whole force is applied in the direttion 

 of the traces of the hindmoft, it cannot have fuch influence 

 on the plough, as when a part of it is in a diredion more 

 horizontal. When a body is to be moved forward in any 

 direaion, the nearer that the diredion of the force applied 

 approaches to the diredion of the body, it afts with greater 

 influence ; and, therefore, as the plough moves horizon- 

 tally, and as the direaion of the united draught of a plough 

 with the cattle yoked two abreaft is more horizontal than 

 the direaion of the draught in a plough with cattle 

 yoked in a line, the fame force applied will have greater 

 influence. 



When thefe two different ways of yoking cattle in 

 ploughs are thus confidered and compared together, it is 

 difficult to determine which ought to be preferred. Each 

 of the two feems preferable to the other in a certain fitua- 

 tion. When the land is ftiff', and the labour fevere, the 

 yoking the cattle in pairs feems preferable, as it is certainly 

 the ftrongeft draught ; and when the land is wet, and in 

 danger of being much hurt by the treading of the cattle, 

 the yoking them in a line before each other feems prefer- 

 able ; as thereby they are confined to the bottom of the fur- 

 row, which is the iirmeft part of the land, and prevented 

 from doing harm. 



In wet lands and feafons, as long teams anfwer beft, for 

 the moft part, collars and trace-chains become of confider- 

 able utility in moft cafes in yoking of cattle ; and in which- 

 ever way neat cattle are geared for work, they fliould con- 

 flantly have bridles or bit-halters, with blinders, as by fuch 

 means they are rendered docile, traaable, and eafy to manage 

 in the bufinefs of team labour. Much information on this 

 fubjea may be feen in the Correaed Report on Agricul- 

 ture for the County of Suflex. 



YOKULS, in Geography, the higheft mountains in Ice- 

 land, perpetually clothed with fnow. Of thefe, Snaefial, 

 hanging over the I'ea on the S.W. part of the ifland, is 

 faid to be the higheft, its height being computed at 6860 

 feet. The mountains are faid to be chiefly fand-ftone, 

 pudding-ftone, with petrofilex, fteatite, and argillaceous 

 fchiftus. 



YOLK, or Yelk, in Natural Htflory, the yellow part in 

 the middle of an egg. See Egg. 



The chicken is formed out of and nouriftied by the white 

 alone, till it be grown to fome bulk : after which the yolk 

 ferves it for nouriftiment ; which it likewife does, in part, 

 after it is hatched. For a good part of the yolk remains 

 after exclufion ; being received into the chicken's belly : 

 and being there referved, as in a ftore-houfe, is by the 

 duaus inteftinalis, as by a funnel, conveyed into the guts, 

 and ferves inftead of milk. Willughby's Ornithol. lib. i. 



"P-3; 



This was even known to Pliny : — " Ipfum animal ex 



Y O L 



albo liquore ovi corporatur : cibus ejus in luteo eft." Lib. x. 

 cap. 53. 



Yoi.K, in Rural Economy, the peculiar munauous fecre- 

 tion which exudes through the flcins of fheep, and which by 

 intermingling with the pile of the wool renders it foft, 

 phable, and in proper condition. It has fomewhat the 

 fame etfea on it which oil has upon a thong of leather, 

 when kept in and perfeaiy faturated with it. The difpo- 

 fition to the produaion of this fubftance in (heep is favour- 

 able to the valuable properties of the wool, aud (hould be 

 attended to by the fheep-farmer in fixing and regulating his 

 ftock. It is noticed by a late writer on Agricultural 

 Chemiftry, that wool often wafhed in calcareous water be- 

 comes rough and more brittle than ufual, as the carbonate 

 of lime has the power of diflblving or decompofing the yolk 

 of it, which is an animal foap that naturally defends it; 

 that the fineft wool, fuch as that of the Spanifh and Saxon 

 Iheep, is moft abundant in yolk ; that M. Vauquelin has 

 analyfed feveral different fpecies of yolk, and has found 

 the principal part of all of them a foap, with a balls of 

 potaffa, that is, a compound of oily matter and potafla, with 

 a httle oily fubftance in excefs ; and that he has likewife found 

 in them a notable quantity of acetate of potafla, and minute 

 quantities of carbonate of potaffa and muriate of potaffa, and 

 a peculiar odorous animal matter. 



The fame chemical writer has ftated, that he found 

 fome fpecimens of wool lofe as much as forty-five per cent. 

 in being deprived of their yolk ; and that the fmaUeft lofs 

 in his trials was thirty-five per cent. 



It is fuggefted in the above work, that the yolk is the 

 moft ufeful to the wool on the back of the fheep in cold and 

 wet feafons ; and that probably the appUcation of a little 

 foap of potaffa, with excefs of greafe, to the fheep brought 

 from warmer climates in our winter, that is, increafing their 

 yolk artificially, might be ufeful in oal'es where the finenefs 

 of the wool is of great importance. A mixture of this 

 fort is more conformable to nature, it is thought, than 

 that ingenioufly adopted by the late Mr. Bakewell ; but 

 that at the time his labours began, the chemical nature of 

 the yolk of wool was not known. See Wool, Washing 

 Sheep, &c. 



Yolk of the Seed, FItellus, in Botany and Vegetable Phy- 

 Jiology, a part firft defcribed by Gartner, and thus named by 

 him, from its fuppofed analogy with the yolk of an egg. 

 This analogy, and even the exiftence of the part in queftion, 

 have been difputed, as Mr. Brown hints, in Prodr. Nov. 

 Holl. V. I. 306, by M. Correa de Ssrra, and by the writer 

 of the prefent article. We have never at any time commu- 

 nicated on this fubjea with our learned and fagacious 

 friend, now the Portuguefe minifter at New York ; fo that 

 we are ignorant how far his objeaions extend, or on what 

 they are founded. Nor does Mr. Brown know more of 

 this matter, than a fimple record of M. Correa's opinion, 

 in De CandoUe's Flore Frangaife, v. i. 157. This coinci- 

 dence, however, from fuch a quarter, gives us great confi- 

 dence in our own opinion, which was firft offered to the 

 public in Introd. to Botany, chap. 19, publifhed in 1807. 

 On a more attentive and full confideration of the queftion, 

 the fame fentiments were more exphcitiy detailed and de- 

 fended in a paper read before the Linnaean Soc. Nov. 3,; 

 1807, and printed in that Society's Tranfaaions, v. 9, 

 204. \ 



Gaertner ftates the Fiiellus, or Yolk of the Seed, to be! 

 " diftina from the Cotyledons, as well as from the yilbumen, • 

 and for the moft part fituated between the latter and the: 

 Embryo." (See Seed, where a reference is made to Vitel 

 Lus, under which head the fubftance of the prefent article 



waif 



