945 



WINE. 



WINE. 



915 



Again, draw YZ perpendicular to BB', or parallel to A'B' ; then 



B'Z(=B'Y cos BB'Y) = Sv' sin- 6, 



Y z ( = B' Y sin B B' Y) = 3 v' sin 8 cos 9, and 



BZ ( = !' B' z) = V 3v' sin- 9. 



But by similar triangles, BZ : z\ : : BB' : B'A', that is 



;' Sv' sin j 8 : 30' sin 8 cos 9 :: v' : v; 

 whence r 8 sin 2 6=3?'' sin 8 cos 8. 



Multiplying each term by v, and for r-, the first term, substituting 

 its equivalent r 2 sin' 6 + r- cos 1 9, we have 



in-' 8 4- r cos-0 3 1- sin-6=3rt>' sin 6 cos 8; 

 or simplifying, and dividing by sin'- 9, we get 



2 r^ + U 2 cotan 8 = 3tV cotan 6, 

 which reduced as a quadratic equation, with respect to 8, gives 



- 

 cotan 6( = tan ABX) = 9^ + (- + 4"^ ' 



The angle ABX will evidently depend upon the relation between i', the 

 velocity of the sail, and r, the velocity of the wind: if t'=o, or the 

 fail is at rest, we should have tan A B X = v'2, that is, the angle ABX 

 would, as above, be equal to 54^ 44' nearly ; and when r' = r, the for- 

 mula gives ABX = 74 19' nearly. It follows that as the velocity of 

 the revolution increases, the inclination of the section wx to the wind, 

 or to the axis of rotation, should be increased. Since, therefore, the 

 velocity of the sail continually increases from the axis to the extremity 

 of the radius or arm which carries it, it is evident that the sail, instead 

 of being a plane, ought to have a curved surface such that the incli- 

 nation of the section to the direction of the wind may increase with 

 its distance from the axis conformably to the values which would be 

 given by the above formula, the ratio between the velocity of the 

 wind and sail at any given distance from the axis of rotation being 

 known or assumed. It was observed by Mr. Smeaton that the velo- 

 cities of the sails at their extremities are often more than twice as 

 great as that of the wind. From several experiments which were 

 made on a great scale by the same engineer.it was found that the effect 

 is very advantageous when the inclinations of the axis, or the direction 

 of the wind, with a section of the sail taken perpendicularly to the 

 revolving arm at different distances from the axis, were as in the 

 ollowing table :- - 



At one-sUth of the length of the arm 



At one-third ,, 



At one-half ,, 



At two-thirds 



At nvr-sizths ,, 



And at the extremity 



M 



71' 



74' 



iy 



Mr. Smeaton found also that when each sail is broader at the further 

 extremity than near the centre, the effect is greater than when it h is 

 the form of a parallelogram ; and that the most advantageous breadth 

 .it the extremity U one-third of the length of the arm. 



There is a certain limit to the quantity of sail which a windmill can 

 carry with advantage ; a j id from Mr. Smeaton's experiments it results 

 that, when the surfaces of all the sails exceeds seven-eighths of the 

 area of the circle described by each arm in one revolution, the velocity 

 is diminished ; probably from the want of sufficient openings by which 

 the wind, after impact, may escape. Mr. Smeaton also found that the 

 ratio between the velocities of windmill sails when unconnected with 

 the machinery, and when loaded so as to produce the maximum effect, 

 is variable ; but, in general, that ratio is as 3 to 2. The velocity of 

 the sails when the effect is a maximum varies nearly with the velocity 

 i> the wind. 



The form and position of the sails remaining the same, the load or 

 resistance when a maximum, varies nearly with the square of the 

 velocity of the wind ; and the maximum of resistance which sails of 

 imiliir figures, and in similar positions^ will overcome at a given dis- 

 tance from the centre of motion, will vary with the cube of the radius 

 or arm of the sail. 



WINE. The chemistry of wine presents many points of interest, 

 and may be treated of independently of its history, manufacture, com- 

 merce, and uses. 



In the juice of the grape, fermentation is excited by the access of 

 ;iir, alcohol and carbonic acid being formed by the decomposition of 

 the sugar contained in the fluid 



(par. 



= 2C,H,O.j + 4CO., 

 Alcohol. Carbonic acid. 



The process once commenced, continues independently of any further 

 influence of the air. In addition to the alcohol and carbonic acid 

 formed by the fermentation of the juice, there is also produced a 

 yellow or gray insoluble substance, containing a large quantity of 

 nitrogen. It is this body which possesses the power of inducing 

 fermentation in a new solution of sugar, and which has in consequence 

 received the name of ferment. [FEHMENT.] The alcohol and carbonic 

 acid are produced, as above indicated, from the elements of the sugar; 

 but the fevment is formed from those azotised constituents of the grape- 

 juice which have collectively been termed yluten. [GLUTEN.] Gluten 

 dissolved in pure water undergoes a process of decomposition ; but the 

 decomposition which it sutlers in an isolated state, and that which it 

 ARTS ASD SCI. DIV. VOL. VIII. 



undergoes when dissolved in a vegetable juice, belong to two different 

 kinds of transformations. There is reason to believe that its change to 

 the insoluble state depends on an absorption of oxygen ; for its sepa- 

 ration in this state may be effected under certain conditions by free 

 exposure to the air without the presence of fermenting sugar. It is 

 known also that the juice of grapes, or vegetable juices, in general 

 become turbid when in contact with air before fermentation com- 

 mences ; and this turbidity is owing to the formation of an insoluble 

 piecipitate of the same nature as ferment. The oxygen consumed in 

 the fermentation of wine or beer is not taken from the atmosphere, 

 though the access of this is necessary to excite it in the first instance. 

 Gluten seems to act towards sugar .is diastase does towards starch, 

 namely, imparts that impetus to it v, hich enables it to alter its con- 

 dition. When both gluten and sugar are present in a liquid, fermen- 

 tation will go on till the decomposition of one or other be complete. 

 When the quantity of ferment is too small in proportion to that of the 

 sugar, its fermentative putrefaction will be completed before the trans- 

 formation of all the sugar is effected. Some sugar here remains unde- 

 composed, as the cause of its transformation is absent, namely, contact 

 with a body in a state of decomposition : this happens in the rins dc 

 liqueurs, the fruity or sweet wines. But when the quantity of ferment 

 predominates, a certain quantity of it remains after all the sugar has 

 fermented, its decomposition proceeding very slowly on account of its 

 insolubility in water. This residue is still able to induce fermentation 

 when introduced into a fresh solution of sugar, and retains the same 

 power until it has passed through all the stages of its own transforma- 

 tion. Hence a certain quantity of yeast is necessary in order to effect 

 the transformation of a certain portion of sugar ; not because it acts by 

 its quantity in increasing any affinity, but because its influence depends 

 solely on its presence, and its presence is necessary until the last atom 

 of sugar is decomposed. 



Climate and soil greatly modify wine both in kind and quality. 

 Differences, however, in the vintage and manufacture often determine 

 the character of wines made in the same district, and cause them to 

 widely differ from each other in odour, flavour, and even colour. Such 

 differences often occur spontaneously, as in the case of amontillado. 



The quantity of azotised matter in the juice seems to be the same in 

 whatever part the grapes may grow ; at least no difference has been 

 observed in the amount of yeast formed during fermentation in the 

 south of France and on the Rhine. The grapes grown in hot climates, 

 as well as the boiled juice obtained from them, are proportionally rich 

 in sugar. Hence, during the fermentation of the juice, the complete 

 decomposition of its azotised matters, and their separation in the 

 insoluble state, are effected before all the sugar has been converted 

 into alcohol and carbonic acid. A certain quantity of the sugar conse- 

 quently remains mixed with the wine in un undecomposed state, the 

 condition necessary for its further decomposition being absent. The 

 azotised matters in the juice of grapes of the temperate zones, on the 

 contrary, are not completely separated in the insoluble state when the 

 entire transformation of the sugar is effected. The wine of these 

 grapes, therefore, does not contain sugar, but variable quantities of 

 undecomposed gluten in solution. This gluten gives the wine the 

 property of becoming spontaneously . converted into vinegar when the 

 access of air is not prevented; for it absorbs oxygen and becomes 

 insoluble, and its oxidation is communicated to the alcohol, which is 

 converted into acetic acid. By allowing the wine to remain at rest in 

 casks with a very limited access of air. and at the lowest possible tem- 

 perature, the oxidation of this azotised matter is effected without the 

 alcohol undergoing the same change, a higher temperature being neces- 

 sary to enable alcohol to combine with oxygen. As long as the wine 

 in the stUling-casks deposits yeast, it can still be caused to ferment by 

 the addition of sugar ; but old well-layed wine has lost this property, 

 because the condition necessary for fermentation namely, a substance 

 in the act of decomposition or putrefaction is no longer present in it. 

 In hotels and other places, where wine is drawn gradually from a c,isk, 

 and a proportional quantity of air necessarily introduced, ite erema- 

 causis that is, its conversion into acetic acid is prevented by the 

 addition of a small quantity of sulphurous acid. This acid, by entering 

 into combination with the oxygen of the air contained in the cask 01 

 dissolved in the wine, prevents the oxidation of the organic matter. 



A knowledge of the facts just mentioned enables us to comprehend 

 the nature and obje6t of the practices adopted empirically for the pre- 

 servation of wine ; above all. of those which are requisite to prevent it 

 passing into the state of acetic acid, to which the wines of northern 

 countries, or poor weak wines, are most prone. Thus, the processes of 

 racking, sulphuring, fining, mixing, bottling, and keeping in cellars the 

 temperature of which is low, are obviously all directed against the 

 occurrence of the acetuus fermentation, as they are mostly inadequate, 

 to check the vinous fermentation, and indeed altogether unnecessary, 

 since so long as the vinous fermentation is going on that is, as long as 

 the alcohol continues to be generated the wine is gaining in quality. 

 Once begun, the presence of atmospheric air is in nowise necessary for 

 the continuation of the vinous fermentation ; in fact, the more 

 thoroughly it is excluded the better, for while the vinous fermentation, 

 by which the wine is ameliorated, goes on, the acetous fermentation 

 cannot commence. 



From the above facts, established in the main by Liebig, it appears 

 that while the azotised matter (gluten) in grapes, wherever grown, is a 



3r 



