_Crushing_.--If the tree is carried from the plantation without being subjected to fermentation, it must be pa.s.sed through a mill, the rollers of which, if made about three feet in length, and one foot in diameter, will be found a very convenient size. In this operation, care should be taken, first of all, to separate the tender from the harder or riper layers of fibre. The tree is composed of different layers of fibre, which may be divided into three sorts; those of the exterior, having been exposed to the atmosphere, possess a great degree of tenacity--whilst those of the interior, having been secluded from the air, are much more soft and tender. If, therefore, the layers of the plantain are pa.s.sed indiscriminately through the mill, those which are hard or firm will not be injured by the pressure, whilst those which are soft will be almost reduced to pulp. Therefore, the rollers of the mill should be always placed horizontally, and upon pa.s.sing the trees lengthways through the mill, the pressure will be uniform and the fibre uninjured. In this manner, pa.s.s the different sorts of layers separately, and the produce will be about four pounds of fibre from each tree. The stalks of the branches of the plantain give the best fibre, and a large quant.i.ty, as compared with the body of the tree; 100 lbs. of the stalk will give 15 lbs. nett of fibre. In general, if a tree will give 4 lbs. nett of fibre, the stalks will give 1 lb.

out of the 4 lbs. The stalks ought also to be crushed separately, because they are harder than the exterior layers of the tree. About 3,000 trees may be pa.s.sed through the mill in a day. Whilst the experiments were in progress it was ascertained that with a single horse, 100 plantain trees on an average were crushed in twenty minutes, giving five minutes rest for the horse.

_Fermentation_.--This operation may be performed in several ways. If the trees are allowed to ferment upon the spot after being cut, a great saving will occur in respect of _carriage_; this matter ought to be carefully studied, because, on an extensive scale of manufacture, it is of serious importance. It is found that the trees when cut and heaped up, are subject to a drainage of juice, which, having a tanning property, discolors those pieces which lie at the bottom; hence much time is consumed in afterwards restoring the fibre to its natural color. The cut plants should be removed from the stumps of the trees, and then placed in heaps, shaded from the sun by laying the leaves over them. They will take several weeks to ferment. To pursue this process in the immediate vicinity of the establishment, would give rise to many inconveniences, in consequence of the very large s.p.a.ce of ground that would thereby be occupied. Fermentation requires a mean temperature. A tree cut down and exposed to the sun, would be nearly dry at about 30 deg.

centigrade, showing a result quite different to that which ought to be obtained; whilst a tree placed on a wet soil, and open for the fresh air to circulate between the plants, covered at the same time with its own leaves, and shaded by the foliage of the plantation, would be decomposed at the desired point of about 22 degrees. The different modes of fermentation require the same proportions. If the cut plants be covered with a thick layer of earth, they will not decompose in six _months_; but if, on the contrary, they are covered slightly, so that they may receive the freshness of the earth, and the heat of the air, they will decompose in six _weeks_. It is the same with the fermentation of alkaline baths. Baths at only _one_ degree will produce decomposition, whilst baths at _three_ degrees will not produce any decomposition. The stuff after being pa.s.sed through the mill, or after fermentation, will be put into the chemical baths, or vats, or chemical liquor, and the persons in charge of the mill and boilers will do this work. Fermentation may be advantageously used, in cases where the trees are grown at a distance from the establishment--but, where they are in the immediate vicinity of the works, it will be best to crush them by the mill. The princ.i.p.al saving that is occasioned by fermentation, will be found in the carriage, as the substance will be much reduced in weight by that process. In an establishment where the manufacture is carried on upon a very large scale, trees cut down at a distance can be fermented, whilst those produced near the mill can be crushed.

_Chemical Agents._--For decomposing the gluten in the trees during the process of boiling, soda, carbonate of soda, and quick lime, are used. The proportions herein given, are those requisite for making three tons of fibre per day, upon which scale the cost price of the fibre in a prepared state for bleaching, is subsequently calculated.

To make three tons of fibre per day, it is necessary to have four boilers of 800 gallons each, and give five boilings in a day, or 1,650 lbs. of nett fibre for each boiler, or 6,600 lbs. for the four boilers per day. After having put into the boiler a sufficient quant.i.ty of water to cover the material, wait until the water begins to boil, and then add the chemical agents.

lbs.

To the first boiling of a copper, put of soda 60 To the 2nd, 3rd, 4th, and 5th boilings of the same copper, 15 lbs., each making 60 ----- 120 ----- Therefore the four boilings will take of soda 480 The same liquid will serve for two other days, by adding 15 lbs. to each fresh boiling, say, in the whole, 40 lbs., or 600 It will consume in soda for nine tons made in three days 1,080 Or 360 lbs. for three tons made in one day.

On the fourth day commence again in the same manner, and go on for the two remaining days as above, producing eighteen tons in the six days. The quick lime is to be employed in each of the boilings, in the proportion of one-third less than the quant.i.ty of soda. Crude soda may be used in the boilings, without previously discarbonising it, and quick lime reduced to lime water; but, to render the action of the chemical ingredients more quick and certain, it is better to discarbonise the soda before it is put into the boiler. This may be done by preparing in a small separate boiler the quant.i.ty of liquid necessary for a day's consumption, which is prepared in about an hour. The carbonisation is effected in the following manner:--

Ten parts of salt of soda. } Six parts of quick lime. } In weight.

Seventy parts of water (never less.) }

_Boiling_.--This is a most important operation. By it the gluten and coloring matter are separated from the fibres, which separation is absolutely necessary, in order to prepare the fibre to receive the bleaching. It is necessary to observe that the three several sorts of layers which are found in the tree, and which, under the head of "crushing," are recommended to be _pressed_ separately, should be also _boiled_ separately, because the outermost layer has more coloring matter than the next under it, which again has more than the innermost layer. As they are boiled so will they be dried and shipped, and each sort will have a different price in the market; that fibre which is lightest in color bearing the preference, in consequence of its not requiring more than _six_ hours to bleach--whilst the darkest will, probably from its greater tenacity, take _twelve_ to _eighteen_ hours. It is advisable to place over each boiler the means of lifting the ma.s.s of fibre when boiled, and suffering it to drain into the boiler before it is carried away to be washed. This is easily effected by a chain from the roof, to which may be hung a lever, having at that end over the boiler some hooks attached to it, whereby the ma.s.s is lifted out of the boiler, and the liquor thus preserved for the next boiling.

_Washing_.--It is absolutely necessary that the fibre should be well washed after being taken out of the boiler, in order that all extraneous matter may be separated therefrom. In choosing the site for an establishment of this kind, care must always be taken to make choice of a spot in the immediate neighbourhood of a large river, or other plentiful supply of fresh clean water. The machinery necessary for cleansing and washing the fibre may be of various descriptions; but, perhaps a selection from one of the three following sorts will be found to answer every purpose, viz., those used by paper manufacturers in England, and by coffee planters and arrowroot growers in the West Indies.

_Drying_.--The washed fibre, when hung over lines made of the twisted fibre, or any other convenient material, will be sufficiently dry in a few hours to be taken down, when more can be hung up, and then several batches can be dried in a day; and it will be necessary to have the drying ground as near the water as possible, in order to save weight in carriage.

_Pressing_.--When the fibre is perfectly dry, it must be well pressed, for the convenience of packing, carriage, and shipment. The hydraulic press is the best machine that can be used for the purpose; but in the absence of that, the lever and screw will make a large amount of pressure available. A hydraulic press of from 400 to 500 tons, will press bales of from four to five hundred weight each, which will not be too large for shipment."

STARCH-PRODUCING PLANTS INVESTIGATED.

Starch is one of the const.i.tuent parts in all mealy farinaceous seeds, fruits, roots, and other parts of plants, and is in large demand for domestic use, the arts, &c. Our common starch is made from wheat, and a good deal from potatoes. Pure fecula is separated by art from a variety of plants.

Of plants yielding starch we have the Indian arrowroot, which is the fecula in the rhizomata of several species of the Marantaceae. In the West Indies it is obtained from the _Maranta arundinacea_, _Allomyca_ and _n.o.bilis_, and also from various species of _Canna_ called _Tous les mois_, and in the East Indies from species of _Curc.u.ma_, and from _Maranta ramossissima_ in Silhet.

The bread fruit (_Artocarpus incisa_), already alluded to, yields a large quant.i.ty of starch; as do the sweet potato (_Convolvulus Batatas_, or _Batatas edulis_). The pith or farinaceous part of the trunk of the _Caryota urens_, is almost equal to the finest sago. In a.s.sam the sago of this palm is much used.

The two varieties of the Ca.s.sava afford a very superior fecula, which is imported under the name of Brazilian arrowroot. 8,354 bags of tapioca and farina were imported from Maranham in 1834. Some excellent starch from Norfolk Island was shown at the Great Exhibition.

The Cycadaceous family yields much starchy matter, along with mucilage. From the soft stems of _Cycas revoluta_ and _C. circinalis_, natives of China and the East Indies, a kind of sago is made. These plants are propagated by suckers. _Zamia pumila_, a native of the Cape of Good Hope, and other species of this remarkable genus of plants, which is nearly related to both ferns and palms, supply an amylaceous matter, which has been sold as arrowroot. A similar product is obtained from _Alstroemeria pallida_, a perennial plant, with pink red flowers, growing in Chili. From the nuts of the _Cycas circinalis_, the Singalese prepare an inferior kind of starch, by pounding the fresh kernels. These are cut in slices, and well dried in the sun before they are fit for use, otherwise when eaten they are intoxicating, and occasion vomiting and purging.

The quant.i.ty of starch in a plant varies according to the period of growth. The results of examination on the comparative yield of starch in the potato, showed that while it abounded towards the latter part of the season, it decreased when the tubers began to germinate in the spring. It was found by Professor Balfour that 240 lbs. of potatoes left in the ground, contained of starch--

lbs. Per cent.

In August 23 to 25 or 9.6 to 10.4 September 32 " 38 " 13.3 " 16 October 32 " 40 " 13.3 " 16.6 November 38 " 45 " 16 " 18.7 April 38 " 28 " 16 " 11.6 May 28 " 20 " 11.6 " 8.3

The quant.i.ty of starch remained the same during the dormant state of winter, but decreased whenever the plant began to grow, and to require a supply of nourishment.

Mr. Harris, of Jamaica, some years ago, made experiments upon the nutritious qualities of the princ.i.p.al roots and vegetables of the West Indies. These being well washed and sc.r.a.ped, were grated, in each case into two gallons of clear rain-water, and the whole then filtered through a clean linen strainer, after which it was left to settle; when the amylaceous matter had wholly subsided the supernatant liquor was carefully decanted, and fresh water added, which process was repeated until every foreign substance appeared to be removed; the produce of these several operations was then carefully collected and dried with a temperature of about 110 deg. Fahrenheit, and, when dry, weighed. In this manner the results given in the following table were obtained:--

PRODUCE FROM FIVE POUNDS OF THE Oz. Drms. Centes. prop.

Root of the sweet ca.s.sava (_Janipha Loeflingii_) 14 1 17.27 Root of ocoes or taniers (_Caladium esculentum_) 11 17 14.29 Root of the bitter ca.s.sava (_Janipha manihot_), the Yucca amarga of the Spaniards 11 2 13.90 Full grown but unripe fruit of the plantain (_Musa paradisiaca_) 11 1 13.82 Root of the Guinea yam (_Dioscorea_ _bulbifera_) 8 6 10.46 Root of the sweet potato (_Batatas_ _edulis_) 8 6 10.46 Root of the arrowroot (_Maranta_ _arundinacea_) 5 6 6.71 The full-grown but unripe fruit of the banana (_Musa sapientum_) 0 0 0.00

This table exhibits, no doubt, very unexpected results, since it places the sweet ca.s.sava at the very top, and the banana at the lowest place in the list, while the bitter ca.s.sava, which seems to be little more than a variety of the sweet, notwithstanding its being the staple material of West Indian bread, occupies two places lower down, and is followed by the plantain. The sweet potato and the yam, both of which are considered to be less nutritious than the arrowroot, rank above it in the centesimal proportion of their amylaceous produce. Upon what, then, do the nutritive properties of these various substances depend?

Is it upon a gluten which was overlooked by Mr. Harris, in his experiments, or, if not, may we not suspect some inaccuracy in the proportion of starch a.s.signed by him to each? It is to be wished that similar experiments were repeated with care in different quarters, and the list extended to other tropical products applicable to human sustenance, especially the roots which yield the farinaceous starch of the South Sea islanders, to the achira of Choco, &c.

I shall extract largely from a very valuable report drawn up by Dr.

John Shier, agricultural chemist, of Demerara, and submitted to the Governor of that colony in 1847, on the starch-producing plants, which is deserving of more widely extended publicity than the merely local circulation it has received. The remarks and results of experiments are worthy of deep consideration; and although they were meant to apply specially to British Guiana, they are equally pertinent to the West India colonies generally, our African and Australian settlements, and many other of our foreign possessions.

For many reasons it is desirable that the number of the staples of cultivation and export of our colonies should be increased. It is the general experience of British agriculturists, that the mixed system of agriculture is more profitable to the farmer and safer for the land, than the continued cultivation of any single crop, or indeed of nearly allied crops; and although fewer valid objections can be urged against the continued cultivation of the sugar cane, when properly conducted, than against that of grain crops, it is nevertheless certain that a well-arranged alternation or rotation of crops would be better. When an efficient system of covered drainage is adopted in British Guiana, there can be no doubt that the sugar cane will be replanted at shorter intervals of time than at present, and that other crops, such as provender crops for cattle, and provision crops for the colonial and perhaps the home market, will be made to alternate in cultivation with the cane. When the cane rows are as far apart as they require to be, to admit of sufficient tillage with the plough and other implements, it will also be possible to intercalate crops of rapidly growing plants; and were this done, as it easily might, in such a manner as to prevent undue exhaustion of the land, or impoverishment of the sugar crop, the returns could not fail to be materially increased. It would then probably be found that the fluctuations in prices would be less felt, for they would not likely, at the same time, affect different crops in the same manner.

It has been ascertained, in regard to some plants at least, that a much larger return can be obtained in the colonies than can be grown in temperate countries, however fertile. This is partly owing to the greater fertility of the soil under powerful tropical atmospheric influences, and partly to the fact that vegetation is continuous throughout the year, so that slow growing plants can do more within the time, from their functions not being arrested by the chill of winter; and of many rapidly growing plants, two successive crops can be grown within the year.

Starch is a substance easily manufactured, and being largely used in several of the arts, as well as an article of diet, there consequently exists a considerable demand for it in England. It may be obtained from a great variety of plants, and many of the most productive of it are natives of the tropics.

The high prices commanded by grain and breadstuffs in Europe, renders the present a remarkably favorable time to ascertain what can be done in this branch of tropical agriculture; for should the potato disease return, or this root be less extensively planted than hitherto, starch must maintain a high price, and it will be worth ascertaining whether some of the superior starch-producing plants of the tropics might not be cultivated to such an extent as to supply the English market, and thus be at once profitable to the colonies and advantageous to the mother country.

Before entering on such a cultivation, however, various points require investigation. We ought to be able to answer such questions as the following:--

1. What differences exist between the characters of starch produced by different plants?

2. What are the qualities or properties that lead manufacturers--calico printers for example--to prefer one variety to another?

3. For culinary purposes, and as an article of diet, what qualities or characters obtain a preference?

4. Can the starches from different plants be distinguished from one another by distinct and well marked characters, so that the subst.i.tution of a less esteemed variety for a more esteemed one, or the adulteration of a high priced variety with a cheaper one, could be readily detected?

5. What plants produce the most esteemed varieties?

6. What plants produce it in the largest quant.i.ty?

7. What plants produce the largest yield per acre?

8. From what plants is it most easily manufactured?

9. Is the process attended with any particular difficulties that ought to deter the East and West India planters from engaging in it?

In the following observations (continues Dr. Shier) I shall be able to reply to several of these questions, especially those capable of being settled in the laboratory. On other points, particularly those relating to the returns per acre, I am at present but imperfectly informed, in consequence of the limited extent to which these plants have hitherto been cultivated in this colony (Demerara), and from the total absence of authentic data regarding the amount of yield.

_Characters of starch produced from different plants_.--Starches from different plants are best distinguished from one another by examination under a good miscroscope. The grains or globules may be examined either as transparent or opaque objects; and although in the same species there are considerable differences in size and form, the different kinds are, on the whole, quite distinguishable. One of the best ways of examining the form of the globules, under the microscope, is to lay them on a plate of gla.s.s and cover them with a drop of aqueous solution of iodine, which renders them gradually blue and opaque. When the difference in size and form between the globules of different species is considerable, as between the _Tous les mois_ starch and ca.s.sava starch, or even between the arrowroot starch and ca.s.sava starch frequently used to adulterate it, it is not difficult, with a little practice, to detect the fraud.

TABLE ILl.u.s.tRATIVE OF THE SIZE AND FORM OF THE STARCH GLOBULES OF VARIOUS PLANTS.

1. Tous-les-mois (_Canna coccinea_).--Grown in Grenada, 1-300 to 1-2,000 of an inch; general size, 1-500; form of the globules, large, elliptical and ovate, and remarkably transparent.

2. Ditto ditto (species unknown).--From a plant grown in the garden of the Hon. J. Croal, Georgetown, but gathered before the root was fully ripe; globules spherical, shortly ovate and elliptical; size, from 1-600 to 1-1,600; general size, 1-800.

3. Buck Yam (_Dioscorea triphylla_).--Grown on the banks of the Demerara River. Form of globules, elliptical, often truncated at one end, so as to be mullar-shaped, some pear-shaped; length, twice the width; size, 1-600 to 1-2,000; general size, 1-800.

4. Common Yam (_D. sativa_).--Grown on No. 1 Ca.n.a.l, Demerara River.

Elliptical, some long elliptical; size, 1-700 to 1-2,000; general size, 1-1,000.