1850.] 



THE CIVIL ENGINEER ilND ARCHITECTS JOURNAL. 



25 



this useful material (for architectural purposes) — which appears to have takea 

 place in the seventh century of the Christian era, — Mr. Donaldson proceeded 

 to describe the different materials and their proportionate quantities as 

 employed in making glass. He then gave a very elaborate description of 

 the various processes connected witli the manufacture of the several qualities 

 known as flint or crystal, crown, sheet and German sheet, bottle or common 

 green, and plate glass. — A number of drawings illustrative of each stage of 

 the manufacture were exhibited. — Mr. Donaldson particularly alluded to the 

 extensive use of the " rough plate glass" for roof lighting, either in the 

 form of tiles or of " lunette domes;" — some of which were exhibited, being 

 5 ft. 6 in. in diameter, from tlie establishment of Messrs. Swinburne. — The 

 Venetian plate, impressed with a diiimond pattern, was also mentioned as a 

 beautiful and useful article for transmitting the light without allowing ob- 

 jects to be seen through it. — The ventilating glass for windows, called the 

 ■' patent perforated," is an admirable invention; the glass panes being per- 

 forated at regular intervals, and thus admitting air v\-hi!e transmitting the 

 light. As an auxiliary to the sanitary improvement of dwellings it may 

 prove valuable, and become generally used. In allusion to the colour ac- 

 quired by plate glass on exposure to the atmosphere, Mr. Donaldson observed 

 that some experiments by Mr. Faraday had proved the cause to be the pre- 

 sence of metallic oxides, which were thus influenced by the atmosphere, and 

 imparted the blue and purple tinge so frequently observable in window panes. 

 Some specimens of glass silvered by a new process patented by Mr. Thomp- 

 son, of Uerners-street, were exhibited, and a deposit of pure silver is ob- 

 tained by aid of saccharine solutions. The expense of this process has been 

 reduced within such limits as give every prospect of its adaptation to a mul- 

 titude of useful and ornamental purposes. The effect of gold, bronze, steel, 

 &c., is readily given by the application of this process to coloured glass. 



A discussion arose from an objection raised by Mr. Tite as to the cor- 

 rectness of the term " plate" being applied to glass which was blown. The 

 question is one on which much difl'erence of opinion exists, but Mr. Swin- 

 burne contended that the term is extensively used in the trade. 



Mr. C. H. Smith offered a few observations on the practicability of cut- 

 ting large squares of plate glass by the aid of a plane-edge saw and very fine 

 sand — which he had ascertained beyond a doubt during the last summer. 



SOCIETY OF ARTS, LONDON. 



Nov. 28 and Dec. 5, 1849. — Benjamin Rotch, Esq., V.P., in the Chair. 



" On the Cultivation and Manufacture of Sugar." By Mr. J. A. Leon. 



The modern agricultural improvements, irrigation and subsoil drainage, are 

 little known in most of the British colonies, and very few of the commonest 

 agricultural implements have been introduced there. The chief alteration 

 which has been adopted is the planting the canes at a greater distance from 

 each other than formerly. The theory of clearing, planting, moulding, and 

 cutting the cane in suitable season is understood, but seldom practised. It is 

 erroneous to suppose that European labourers cannot endure the climate in 

 the sugar-growing colonies, and European emigration ought to be encou- 

 raged. The first improvement in the West Indies should be the organisation 

 of a new system better adapted for emancipated negroes. The planter of the 

 present day cannot do better than lease his fields to a set of negroes, on con- 

 dition of their planting for him three-fourths of the land with sugar-canes; 

 so that the negroes will be dependent for support on the produce and its 

 quality, and will not fail to cultivate the Ian in a proper manner; the owner 

 of the estate erecting improved steam-machinery, giving up the cultivation 

 of the land, and remaining a sugar-manufacturer. The ex-planter, in his 

 new establishment, will then no longer require hired negroes, for the people 

 of his manufactory being British emigrants, the colonial sugar will be pro- 

 duced by Creole growers and European manufacturers. Small West India 

 proprietors should join their lands, so as to form a farm of 700 or 800 acres, 

 to be cultivated as before mentioned, and erect thereon a central sugar ma- 

 nufactory capable of working the produce from 500 acres of sugar-canes, 

 which will be, on an average, 1,000 tons of Muscovado sugar from 10,000 

 tons of canes. Thus they would farm in a small space, and manufacture 

 with powerful machinery, in which consists the required agricultural im- 

 provements, and isolated estates might send their concentrated saccharine 

 matter, or crude sugar, to a parochial central factory. 



The cultivation of the sugar-cane requires more labour than other plants, 

 and in that respect a cane-field may be compared to a garden, and, like it, 

 requires constant care and attention. 



The woody part of the ripe sugar-canes is generally consumed as fuel in 

 the process of manufacturing sugar; other portions are used as seed, forage, 

 and manure, the green leaves being given as food to cattle. It is found that 

 100 lb. of canes generally yield 50 lb. of juice ; these 50 lb. of juice produce 

 by the old process of manufacture 5 lb. of Muscovado sugar and 5 lb. of 

 molasses scum ; the remainder, 40 lb., is the quantity of water to be evapo- 

 rated by the manufacturing process. 



Nothing can surpass the slovenly, unscientific way in which sugar is made 

 on those estates where the common process is in use : and in the whole 

 British dominions only four sugar plantations have received complete steam- 

 machinery. The author recommends steam, not only as a moving power, 



but also for heating and evaporating purposes, and refers to a Colonial 

 Steam Generator, which he has invented, as answering every purpose that caa 

 be required ; but this modern apparatus will be only beneficial when worked 

 on a large scale. 



In sebcting the ground on which a manufactory is to be erected mainly 

 depends its future success. 



The essay then describes the various existing mills made use of in the ma- 

 nufacture of sugar, of which the chief defects are — 



1. Overspeed in motion. 



2. Mismanagement in feeding. 



3. Incflicicncy of the moving power. 



The great price of coal, however, in the West Indies, being 2/. 18s. per 

 ton (when used), renders the working of steam-power very expensive ; how- 

 ever, the steam may be economised and employed in subsequent processes. 



The essay proceeds to describe the Steam Defecator, and other apparatus 

 employed in the manufacture of sugar, and the advantages peculiar to each. 



A great improvement in sugar manipulations, even greater than the con- 

 centration in vacuo, is the application of Animal Charcoal for manufacturing 

 and refining sugar. The discovery of revivification allowing the same carbon 

 to be used again enables the refiner to produce the best quality of sugar from 

 the raw material by a single operatioti : and by improving on the same prin- 

 ciple of filtration, the colonial manufacturer will succeed in producing refined 

 sugar direct from the cane, and thereby dispense with the secondary mani- 

 pulation in Europe. 



Concentrated cane-juice, containing more than 50 per cent, of saccharine 

 matter, will be altered if boiled at a high temperature, or re-concentrated at 

 a low one ; but if boiled in vacuo, the saccharine liquid may be rapidly con- 

 ceutrated at evena low temperature. The author recommends the use of 

 Clark's Condenser, in which the steam is distributed all at once, in 216 ver- 

 tical pipes, radiating to a single collecting pipe, communicating with the air- 

 pump, — and a double-evaporation apparatus constructed by himself, and 

 operating, 



1st. Without alteiing the saccharine matter, as well with a minimum as a 

 maximum of water. 



2nd. Without borrowing any water. 



3rd. Without requiring active superintendence, and saving fuel to a large 

 amount. 



In building a sugar manufactory, the main flue of the steam generators 

 should pass close to the curing-house wall before reaching the chimney, — 

 cast-iron tubes lying across the flue, having one end in the curing-house, 

 whilst the other receives the outside air, being heated from the caloric from 

 the furnace, warms the inner air passing from the yard into the curing-house. 

 Thus a hot-air apparatus is formed with great economy. The direct bleaching, 

 i. e. the artificial mode for separating the liquid from the solid sugar, is done 

 by sprinkling water on the sugar with a small instrument made for that pur- 

 pose ; and, according to tlie number of ablutions, this operation will produce 

 crushed lumps, or stamped loaf-sugar. 



The modern steam apparatus for manufacturing sugar with profit requires 

 the fulfilment of several conditions : 



During crop-time, continuous work night and day, — from whence three 

 advantages arise : 



1st. The cane.juice does not become sour, as when standing during the 

 whole night in the heated apparatus. 



2nd. Fuel is saved, because the fire has not to be re-lit. 



3rd. Double work being done, the expenses of the machinery are reduced 

 50 per cent. 



A better class of labourers must be procured, and work for the whole year 

 round provided for them. 



Mr. Leon is of opinion that nothing but such a total change can restore 

 the British sugar colonies ; and to prepare for this, two things are necessary : 



1st. A thorough knowledge of the modern art of building, erecting, and 

 working tlie improved apparatus. 



2nd. Regular theoretical and practical information on sugar manipulation 

 for the instruction of colonial factory managers, to be given in a London 

 laboratory, furnished with the necessary utensils for working on a small 

 scale. The sugar for expeiiraent should be extracted from the beet-root,^ 

 the juice of which is nearly identical with that of the sugar-cane. 



The essay was accompanied with numerous drawings and models, illustra- 

 tive of the apparatus and processes referred to. 



Dec. 12. — T. Webster, Esq., V.P., in tlie Chair. 

 " On the Application of Electricity to the Arts and Scienas." By Mr, 



HiGHTON. 



The paper was illustrated by beautiful speoimens of simple and compound 

 deposits as applied to works of art ; also specimens of electrotyping, as ap- 

 plied to the preservation of animals, insects, and plants. A beautiful elec- 

 trotype cast from a daguerreotype plate was aUo exhibited. Mr. Highton thea 

 alluded to the application of electricity to the art of war ; to the freezing of 

 water; to the formation of hail; to the ventilation of coal-mines; and 

 finished by showing, that from the fact of electricity differing from all other 

 known forces of nature in its property of producing direct circular motion, 

 it became a most valuable analytical test for ascertaining yvhether certain 

 other foices weie simple and direct, acting in one stiaight line, or the re- 



5 



