The Commercial Products of the Vegetable Kingdom Part 23

I shall say no more on this subject, but will proceed to consider the mode of tempering and clarifying cane juice, and the action of lime on the various substances contained therein. The expression "tempering"

has, I presume, been, adopted in consequence of the use of tempered lime for the purpose of precipitating the feculencies, held in solution in the cane juice, into a state of suspension; and clarification is the process by which we afterwards clear the liquor of these and other foreign matter. Now, as I before observed, "fermentation should be most strictly guarded against;" our first efforts should be directed to free the cane juice from those substances most conducive to that process; and on inquiry we find these to be alb.u.men and gluten; so far, however, from getting rid of them in cold tempering, we adopt a course which retains them permanently in solution, as lime has the power of rendering them permanently soluble, and of forming soapy compounds with resin, wax, and chlorophyle, or the green coloring matter of leaves, forming an insoluble compound with and precipitating only the starch, and converting at the same time the green color of the chlorophyle (which is, in all probability, attached to the resin), into a dark brown, of a greater or less intensity, according to the composition of the cane juice, and, consequently, the quant.i.ty of lime required; it follows, therefore, as a matter of course, that if juice be tempered before these substances have been removed, they must be permanently retained, and they have all the power of preventing granulation.

Alb.u.men, and gluten are both coagulable by heat; if, therefore, we raise the liquor to the boiling point prior to applying the lime, taking care to remove the sc.u.m as soon as it shows signs of breaking, and continuing the boiling until the sc.u.m thrown to the surface becomes inconsiderable, we shall find that the alb.u.men and gluten, in coagulating and rising, have carried with them the small particles of woody fibre, the wax, and a large proportion of the coloring matter, and that the lime will now throw down the starch, and any other little impurities remaining in suspension in the liquor, leaving it perfectly clear and bright. Tempering is an exceedingly delicate chemical operation, and I have no hesitation in saying, that on its proper performance depends the quality of the produce. The following simple experiments, which all have it in their power to try, will, if they give themselves the trouble, fully satisfy them of two important points--the superiority of the hot over the cold mode, and the necessity for great attention to the operation of tempering. Let them take a tumbler of cane-juice and a bottle containing lime water, add the latter to the former by drops, pausing and stirring between each, and they will find that, after the addition of a certain quant.i.ty, the opaque gummy appearance of the liquor undergoes a change, and the impurities contained in it separate into flakes, which increase in size with each drop of lime added, until they become extinct, and the supernatant liquor perfectly transparent; this is the precise point at which the liquor is tempered, and each drop of lime added after this, causes the flakes to diminish rapidly in size, at last entirely to disappear (being re-dissolved), and the liquor to resume its former gummy appearance; it is, therefore, evident that there should be no such expressions as tempering high or low.

The reason why some liquor is so difficult to clean is, that it is either tempered high or low; if it be exactly tempered, the impurities contained in it being entirely separated and thrown out of solution, rise to the surface immediately on the application of heat, and are easily removed; but if there be too little lime, a great portion remains in solution, and if too much, a proportional quant.i.ty is re-dissolved; and in either case cannot be removed by any mechanical means. It is, therefore, necessary to have some precise test for the application of lime.

As regards the superiority of the hot over the cold tempering, let any one take, in separate vessels, two gallons of cane-juice, and temper one, adding the lime in small quant.i.ties--say, of three grains at a time--and keeping an account of the quant.i.ty used; he will find that the first portions produce no effect whatever, and that it is only after the addition of a considerable quant.i.ty that the desired precipitation of the impurities manifest itself. Why is this? Because alb.u.men, gluten, resin, and chlorophyle, being soluble in lime, lime is equally so in them, and they must first be saturated before it will produce any other effect. Let the liquor thus tempered, be then placed on one side. Put the other gallon over a fire, and boil it, removing the sc.u.m just before, and during, ebullition; let it then be taken off the fire, and tempered in the same way as the other. The very first quant.i.ty of lime added causes the appearance of the floccy precipitate; and if the addition of the lime be continued until it be precisely tempered, it will be found that the hot possesses the following advantages over the cold-tempered liquor:--In a quarter of an hour its impurities will have subsided to a sixteenth of its bulk, leaving the supernatant liquor as bright and clear as pale brandy; while those in the other have only sunk to one-quarter of its bulk.

The color of the former clear liquor will not be less than one-half the intensity of that of the latter. The lime used in the hot has been less by one-third than the quant.i.ty used in the cold tempering.

Of course, on level estates there is little difficulty in tempering liquor, but on hilly properties scarcely two pans will require the same quant.i.ty.

It is generally believed that the object of adding lime to cane-juice is for the purpose of neutralising an acid, and it is to the reception of this fallacious idea that it is indebted for its long and continued use, and the present backward state of sugar manufacture is attributable: I unhesitatingly a.s.sert that, if there be an acid present in the cane-juice, the addition of lime to it will be injurious instead of beneficial. There are only four acids that we could expect to find in cane juice--mucous, saccholactic or saclactic, oxalic, and acetic acids. The three first named of these, however, have never been traced, even in the most minute quant.i.ties; and if the latter be present, which, unfortunately, is but too often the case, the addition of lime would only result in the formation of acetate of lime, which is, as I have already observed, an exceedingly difficult crystallisable, very soluble, and deliquescent salt. It has a bitter, saline taste; 100 parts consist of 64.5 acid, 35.5 lime, and it is easily recognisable by its taste in the mola.s.ses made from sour cane-juice: so that, supposing the cane-juice sour, every pint of acid present would require nearly half a pound of lime for its neutralisation, independent of the quant.i.ty required for the tempering or precipitation of the feculencies contained in it, and would result in the formation of one-and-a-half pound of the above mentioned highly deleterious salt.

Suppose we boil the cane-juice prior to tempering it, we then drive off a great portion of acetic acid, much less lime will be required, and if we could, by filtration or subsidence, get rid of the precipitated feculencies, we should make a tolerably good sugar; but as, under the present plan, we have no means of so doing, the acetic acid, which is forming during the whole process of evaporation (as fermentation still goes on), unites with the lime before it can be dissipated by the heat, and thus not only forms acetate of lime, but causes the re-solution of the precipitated feculencies, thus rendering it necessary to add a fresh portion of lime in the tache, a proceeding always to be avoided, if possible, but generally necessary in boiling down sour liquor. Take a small portion of cane-juice (hot or cold) in a tumbler, and temper it with lime until the feculencies are precipitated and the flakes perfectly visible, then add vinegar by drops, and it will be found that the flakes will speedily disappear and be re-dissolved, showing that lime has a greater affinity for acetic acid than starch, and that, although when added to sour cane-juice, it neutralises the acidity, still that result is a consequence, not the cause, of the application, and is highly injurious. Lime is one of the greatest known solvents of vegetable matter; it dissolves alb.u.men, gluten, gum and lignin, or woody fibre, forming soapy compounds with wax, resin, and, chlorophyle. Ordinary cane-juice contains about three parts of resin to every 100 of sugar, and the projection of a small piece of soap into a tache full of granulating syrup will soon convince any one of the effect likely to result from the presence of that material. Although, by tempering hot, we get rid of a very great quant.i.ty of the substances on which lime acts injuriously, a considerable portion of them remain in suspension, the quant.i.ty of alb.u.men contained in the cane-juice not being sufficient to carry them all off by coagulation; on the addition of the lime, however, they are entirely dissolved and as the impurities left behind consist chiefly of gluten, the liability of the liquor to ferment is greatly increased by its retention, that being the fermenting principle contained in wheat and other vegetable productions p.r.o.ne to that process.

One hundred parts of Alb.u.men consist of Carbon, 52.88; Oxygen, 23.88; Hydrogen, 7-54; Nitrogen, 15.70. Gluten, nearly same as Alb.u.men.

-------------+-------+-------+-------+---------+-------++------+-------- 100 parts | | | | | ||Excess! Excess consist of |Carbon.|Oxygen.|Hydro- | Carbon. | Water.|| of | of | | | gen. | | ||Oxygen|Hydrogen -------------+-------+-------+-------+---------+-------++------+-------- Lignin, or | | | | | || | Woody Fibre| 51.45 | 42.73 | 5.82 | or51.45 | 48.55 || | Starch | 43.55 | 49.63 | 6.77 | 43.55 | 56.45 || | Sugar | 42.47 | 50.63 | 6.90 | 42.47 | 57.53 || | Gum | 42.23 | 50.84 | 6.93 | 42.23 | 57.77 || | Alcohol | 51.98 | 34.32 | 13.70 | 51.98 | 38.99 || | 9.03 Acetic Acid | 50.22 | 44.15 | 5.63 | 50.22 | 46.91 || 2.87 | Resin | 75.94 | 13.34 | 10.72 | 75.94 | 15.16 || | 8.90 Wax | 81.79 | 5.54 | 12.76 | 81.79 | 6.30 || | 11.01 -------------+-------+-------+-------+---------+-------++------+--------

By a reference to the foregoing table it will be easily understood how slight a change in the proportion of the ingredients of any one of the substances contained therein will convert it into an entirely different one. In chemistry we are able, to a certain extent, to imitate the operations of nature; but we must follow in the same course laid down by her; thus, we can convert woody fibre, or sawdust and starch, into sugar, gum, alcohol, and acetic acid; but we cannot convert alcohol, acetic acid, or gum into sugar, starch or woody fibre; and of such importance is a slight alteration of the proportions of these elements--carbon, oxygen, and hydrogen--that the abstraction of carbon from sugar, and the addition of a portion of the prime support of life, vegetation and combustion, oxygen, changes the harmless sugar into the most violent of poisons, oxalic acid, which consists of 26.57 carbon, 70.69 oxygen, and 2.74 hydrogen.

Let us now examine the action of lime on sugar, and we shall find it equally, if not more, injurious than on the other substances. Sugar is capable of dissolving half its weight of lime, by which its sweet taste is destroyed, and it becomes converted into gum; the lime abstracting carbonic acid from it to form a carbonate of lime or chalk. It will be seen by the above table that--

100 parts of sugar contain 42.47 carbon.

100 parts of gum contain 42.23 ditto.

----- Difference 24

So that, if we extract 24-100ths of a grain of carbon from 100 grains of sugar, we convert them into gum. Let us suppose that about two ounces of lime, or say 1,000 grains, remain in solution in a pan, (say 200 gallons of liquor,) those 1,000 grains of lime will require 761 of carbonic acid to convert them into carbonate of lime or chalk, 100 grains of which consist of 56.2 lime and 43.8 carbonic acid. So that 1,761 grains of chalk consist of 1,000 lime and 761 carbonic acid. Now 100 grains of carbonic add consist of 27.53 carbon and 72.47 oxygen; therefore 761 grains will consist of 209.50 carbon and 551.53 oxygen.

Consequently, 1,000 grains of lime will require 209.50 grains of carbon to convert them into carbonate of lime; and as we have seen that the abstraction of 24 from 100 grains of sugar convert them into gum, it follows, that the abstraction of 209.50 grains would have a similar effect on 87,000 grains, or about 15 lbs. of sugar, which, being converted into gum, would prevent the crystallisation of several times its weight of sugar; and this is the cause of the formation of mola.s.ses. The loss of sugar is not the only bad consequence of the use of lime, as the greater the quant.i.ty of gum in the liquor, the more it must be boiled--the more it is boiled the darker it gets--and the higher the temperature at which the skip is struck, the smaller the grain. The following is a good proof that lime dissolves alb.u.men, and becomes converted into chalk:--Take a spoonful of syrup out of the tache of any estate on which the liquor is tempered cold; it will be found filled with small flakes; these are alb.u.men set free from its solution in the lime by the conversion of the latter into carbonate of lime, and coagulated by heat. It is perfectly possible to temper liquor, so that scarcely any uncrystallisable sugar will remain; but planters do not like this; they must have mola.s.ses for the still-house; they could, however, boil low, by which the grain and color would be improved, and plenty of uncrystallised, although not uncrystallisable, syrup would be left to take the place of mola.s.ses.

I think I have now fully proved the following facts, viz.:--That the use of lime in sugar-making is not to neutralise an acid; that if acidity be present, the application of lime is injurious; that its action on gluten, alb.u.men, wax, resin, and chlorophyle is equally so; that by decomposing the sugar and forming gum, the quant.i.ty of mola.s.ses or uncrystallisable sugar is much increased, whereby high boiling is rendered necessary, with its consequent heightening of color and injury to the grain of the produce, and that therefore it is perfectly unfit for the purpose of tempering cane-juice.

Messrs. Thomas Begg and Co., of London, have procured from E.F.

Telchemacher and J. Denham Smith, an a.n.a.lysis of one gallon of ordinary plantain juice, and one gallon of Ramos' prepared plantain juice "for the purpose of ascertaining whether any substance can be used which, in conjunction with water, will answer as a subst.i.tute for the plantain juice in the receipt which accompanied the samples." The chemists say they find that one gallon of ordinary plantain juice holds in solution;--

Extract similar to tannin 25.60 grains Vegetable extract and fatty matter 57.70 "

Carbonate of potash 150.40 "

Muriate of potash 33.60 "

Muriate of soda 2.00 "

Silica 1.20 "

------------- Contents of one imperial gallon 270.50 grains

--whilst one gallon of "Ramos' prepared plantain juice" contains, besides vegetable extract, 226 grains of solid matter, consisting of sulphuret and potash, in the following proportions:--

Sulphur 40 grains Lime 156 "

Potash 30 "

---------- 226 grains

They do not think it likely that the potash exists in fresh plantain juice as carbonate, but rather that this salt is the product of decomposition, arising from a compound of potash and a vegetable acid, such as tartaric or oxalic acid present in the fresh juice; be this as it may, any utility derivable from the plantain juice is evidently owing to the potash it contains.

They then give as a subst.i.tute for Ramos' liquid, and to be used in a similar way, the following--

Take of subcarbonate of potash 2 ounces, avoirdupois; sulphur, 2 ounces; best British lime slaked, 1 lb.; mix them into a paste in an earthen pan or wooden tub, with one quart of water (warm) and when thoroughly mixed, pour in ten gallons of boiling water--rain water is the best to use--and stir from time to time until it has cooled, when it may be drawn off from the sediment and kept for use. If rain water cannot be obtained, the purest water obtainable may be used.

One of the causes most fatal to West Indian prosperity, is that exuberance of advantages which they enjoy from serenity of climate and fertility of soil--causes which, in the absence of proper stimulus to industry and improvement, have led to an improvident system of cultivation, and to a blind and ignorant adherence to wasteful methods of manufacture.

The cane is believed to contain from 90 to 95 per cent. of its own weight of saccharine juice; and yet (as Mr. Fownes, a Professor of Practical Chemistry in University College, London, informs us, in an excellent paper "On the Manufacture of Sugar in Barbados,"[17] from which much of what follows has been borrowed) owing to the defective construction of the mills, hardly so much as 50 per cent. is obtained, although he believes it practicable, by an improvement in the mills, to obtain from 70 to 75 per cent.; and of the remaining 10 or 15 per cent. which he regards it as impossible to extract, much, if not the whole, might, I conceive, be obtained, by macerating the pressed canes or mega.s.s, as it issues from the mill, and repa.s.sing it through the rollers; and, be it remembered, that from 40 to 45 per cent. of saccharine juice is nearly, if not altogether, equivalent to a similar per centage of sugar; so that by these initiatory improvements alone, and with little additional trouble, the produce of sugar might be nearly doubled from any given quant.i.ty of canes.

From the action of lime-water when added in a slight excess to the cane juice or raw liquor, as it is vernacularly termed, immediately on issuing from the mill, as well as from the effect produced by ammonia or potash, this liquid appears to contain a considerable quant.i.ty of cane sugar, mixed with much glucose, or that saccharine matter which is found in fruits; gum or dextrine, phosphates, and probably malates of lime and magnesia, with sulphates and chlorides, potash and soda, and a peculiar azotised matter, allied to alb.u.men, which forms an insoluble compound with lime, is not coagulable by heat or acids, and runs readily into putrefactive fermentation.

To free it from these const.i.tuents, and enable it to yield pure and crystallisable sugar, the liquor, on entering the boiling-house, is received into the first of three clarifiers, of the capacity of from three hundred to a thousand gallons each. Here it is subjected to the action of lime-water, which checks the tendency to fermentation, and neutralises any free acid which it may contain. "The common defection process," says Mr. Fownes, "in careful hands, seems susceptible of little improvement. Many other substances than lime have been proposed and tried with more or less success, some of which, in particular states of the cane juice, may prove very useful; but, for general purposes, nothing seems to answer so well as neutralisation by lime, either in the form of lime-water or milk of lime, added until the slightest possible tendency to alkalinity, as ascertained by delicate reddened litmus paper, is perceived. The juice should be somewhat heated before the lime is added, and afterwards raised quite to the boiling point. The fire is then to be withdrawn, and the whole allowed to rest a short time." Such is Mr. Fownes' description of the process of clarification; to which I will venture to add, upon the authority of those who have experienced its good effects, the joint use of the mucilage of the _Guazuma ulmifolia_, or gun-stock tree, as it is popularly termed in Nevis from the use to which its timber has been applied. This is the b.a.s.t.a.r.d cedar of Jamaica, or Orme d'Amerique, and Bois d'Orme of the French, which may be found described by Lunan, in the first volume of his "Hortus Jamaicensis," page 59, under the name of _Bubroma Guazuma_.

This tree presents in the interval between its outer bark of sap-wood, a ma.s.s of fibrous matter about half an inch in thickness, richly impregnated with mucilage, which is obtained by macerating the fibrous ma.s.s, conveniently divided into small shreds, for about twelve hours, in warm water, in the proportion of about two handsful to eight gallons of water. Of this solution, which is of a light, straw color, and somewhat thickened, one gallon is to be added for every hundred gallons of cane juice, after the clarifier has been charged with the proper quant.i.ty of lime-water, and has become lukewarm. The mixture should then be stirred, and afterwards allowed to settle till the sc.u.m has risen to the surface. The fire must next be cautiously and gradually raised to the point of boiling, when it must again be slackened, and the whole left to stand for about forty minutes, by which time the ma.s.s of feculencies will have risen to the surface, when the clear liquor underneath may either be drawn off by a siphon or c.o.c.k; the whole may be filtered as Mr. Fownes recommends, by which means the liquor would be more effectually clarified, and much, if not all, the subsequent labour of skimming dispensed with. The matter remaining on the filter may be employed, either as a ferment in the still-house, or added to the manure heap. Much of the beneficial effect of the mucilage of the _guazuma_ arises probably from an admixture of tannin, or some other astringent; for I have often been struck with the peculiar whiteness of the potted sugar in the curing-house, in the immediate vicinity of the Banana stalks, resulting, no doubt, from their powerful astringency; and tannin has already been found useful in the manufacture of sugar from beet-root in France, and is no doubt equally applicable to cane-sugar.

The liquor, when clarified in the manner described, must be concentrated, by regulated evaporation, to the degree requisite for crystallisation. This Mr. Fownes advises to be done by steam of a moderate pressure circulating in a spiral of copper-pipe laid at the bottom of the evaporating vessels, which should be large and shallow, and wholly unlike those in present use. Here it may be rapidly boiled down till the heat rises to about 225 deg., without risk of burning.

When cold, it should have a density of about 1.38, and mark the 38th degree of Baume's hydrometer; beyond which point of insp.i.s.sation it would be dangerous to go. The remaining concentration will be most safely conducted in the vacuum pan, where a scarcity of water does not, as in Barbados, militate against its use.

Mr. Fownes exposes the absurdity of using shallow coolers, exposing a large surface, and producing a rapid evaporation, for the process of crystallisation. By the use of the shallow coolers formerly, and, I believe, yet to be found on most estates, from the rapidity of the evaporation, the sugar is obtained in a ma.s.s of confused and imperfectly-formed crystals, entangling in their interstices a considerable quant.i.ty of mola.s.ses, which impairs the color of the product, and escaping slowly, and with difficulty, is, to a considerable extent, lost on the homeward voyage by drainage into the hold, occasioning much positive loss to the owner, and giving the bilge-water a most offensive odor. He therefore recommends the use of deep vessels, and avoidance of all agitation in this part of the process, so as to enable the crystallisable portion of the syrup to effect a more complete separation from the uncrystallisable portion or the mola.s.ses. By this simple method, not only sugar of a finer and whiter quality would be obtained, but a large per centage of loss both of crystallisable and uncrystallisable sugar at present caused by the leakage of the hogshead into the hold, would be prevented, not only to the great advantage of the planter, but to the great comfort of the captain, pa.s.sengers, and crew of the vessel freighted with it.

It is not improbable that, by re-boiling the mola.s.ses in the vacuum-pan, and employing tannin in the manner adopted in the process for making sugar from beet-root, from one to five per cent. of crystallisable sugar could be recovered from it, and this per centage might possibly even be found to admit of increase by the further treatment with lime-water and the gun-stock tree s already suggested, for the first clarification of the liquor received from the mill. With this view, Mr. Fownes recommends the subst.i.tution of puncheons, or casks, for the mola.s.ses cisterns ordinarily employed in the curing-house, to receive the mola.s.ses as it drains from the new sugar, and thus retaining it until after the busy period of crop time has closed.

Should sugar of a whiter quality than the ordinary muscovado of commerce be desired, this advantage may be readily obtained, as Mr.

Fownes judiciously observes, by filtering the thin syrup, ready for the vacuum-pan, through a bed of fine charcoal, as is done by the sugar refiners, and afterwards was.h.i.+ng the crystals of sugar with white syrup, when the mola.s.ses has thoroughly drained from them. By this process, which, however, is attended with some increase of expense, and may not, in consequence, be always advisable, muscovado sugar may be obtained, of a quality hardly inferior to that of refined sugar. Mr. Fownes thus sums up the princ.i.p.al points to which he is desirous of calling the attention of the intelligent and enterprising planter.

1. "To obtain, by the use of a properly-constructed mill, the greatest possible amount of juice from the cane."

By this, according to Mr. Fownes, a gain of from 20 to 30 per cent., equivalent to as much marketable sugar, may be obtained without any additional expense; but as, from Mr. Fownes' own showing, there is a residuum of 10 to 15 per cent of liquor obstinately retained by the mega.s.s, or cane trash, after the most powerful pressure to which it can be subjected; much, if not all, even of this loss might be prevented by subjecting the mega.s.s, on issuing from between the rollers, to the action of water for a brief time, pa.s.sing it once more through the mill, and adding the saccharine solution so obtained, or that obtained directly from the cane on its first crus.h.i.+ng. The water thus employed would serve for many successive portions of mega.s.s, until at length it became so richly loaded with saccharine matter as to be worth attention in the boiling-house; or, at all events, it would be serviceable for the cattle, who would fatten rapidly upon it.

By this additional process a further gain of at least five per cent.

might be expected, raising the total gain from improvements in this _first_ stage of the process, to from 25 to 35 per cent.

2. "To clarify and filter this juice with expedition, and to evaporate it rapidly, either over the open fire or by steam heat, as far as it can be done with safety."

By the use of steam, not only is a vast economy of fuel effected, but the temperature is maintained at a uniform and sufficient standard, and the liquor effectually guarded against the risks of carelessness or ignorance. Coal may be obtained on far cheaper terms, in exchange for produce, from the United States or from Cape Breton, than from England; and as colliers from those quarters would find it their interest to bring cargoes at their own risk, and take return cargoes of sugar, rum, or mola.s.ses, at the market price, the planter will be doubly a gainer by the system, obtaining his fuel at a reduced rate, and having his trash and mega.s.s left free as manure for the use of his cane fields.

3. "To complete the concentration in a vacuum pan, or by other means, at a moderate temperature, not hurtful to the sugar, and facilitate the natural process of crystallisation, so as to obtain sugar of a large and distinct grain."

4. "To drain and dry the sugar perfectly, and to save all the mola.s.ses."

The advantages to be antic.i.p.ated from these improvements, superadded to an improvement in cultivation, cannot be estimated at less, upon a moderate calculation, than from 150 to 200 per cent. of increase in the production of sugar, with hardly an appreciable increase of labor or expense; for we have, in the first place, a gain by improved culture of, at least, two hogsheads an acre in sugar, equivalent to 100 per cent.; in the next, by employing improved mills and extracting the residuum, 30 per cent.; by conducting the process of manufacture more judiciously, 10 per cent.; and by the prevention of waste during the transit to market, 10 per cent., making a total of at least 150 per cent.

The common sugar-mill consists of three cylinders, tightened either by wedges, if in a wooden frame, or by screws in a cast-iron frame. If in an iron frame, the above-mentioned noise is obviated, but the friction and loss of power is the same, which is ascertainable by subsequent investigation. The cylinders or rollers, which are moving either horizontally or vertically, are from eighteen to twenty-four inches in diameter, with bearings or shafts of one fourth of their diameter. If the bearings or shafts of the cylinders were of less substance, they could not resist the great strain to which they are subjected when in operation. The whole of the prime mover (steam-engine, water-wheel, or animals), minus the friction of intermediate machinery, is transmitted to the plains of these rollers and resisted by their bearings; hence the action is equal to a weight moving on low wheels of eighteen or twenty-four inches in diameter, on axles of from four to six inches thickness, which weight is equal to the force applied; consequently, if the strain is greater than the resistance of the rollers or the bearings, they must be wrenched off, or if greater than the force applied, the mill will be stopped. The power necessary to move weights upon wheels, on a smooth and level surface, is in proportion to the respective diameters of wheels and axles. The same pull which moves one ton at a given velocity upon a wheel of two feet, with an axle of six inches, will move four tons, if on a wheel of four feet diameter, with an axle of six inches. Consequently, cylinders of small diameter, with strong and substantial bearings, are only admissible as working machines, if no other mechanical means are applicable, as, for instance, in rolling out metals, compressing the surface of various bodies for a glossy appearance, or, generally speaking, to produce a certain and equal form of the substance which is pressed and pa.s.sed between them. They compress the atoms of bodies, and for this reason alone are ill suited to separate the fibres of the sugar canes, and to express effectively the saccharine matter between them. A practical proof of this demonstration is furnished by every sugar cane which has gone through the mill. Fresh mega.s.s is at present better suited for fattening animals than for fuel under the sugar pans.

The loss of material thus sustained, which is, on an average, equal in every mill, whether driven by steam, water, or animal power, is entirely chargeable to the construction of the mill, and amounts to about ten per cent. of the saccharine matter contained in the sugar canes.

M. Duprez, an agent of the French Government, having experimented on the canes in Guadaloupe, found the quant.i.ty of juice in every 100 lbs.

crushed--