Gas-Lights. Illuminating Powers of Coal and Oil-Gases. Comparative To compare the expence of oil-gas with that obilluminating tained from coal, a knowledge of the comparative powers of illuminating powers of equal bulks is necessary. It is Coal and Oil-Gases. Gas from Coal Tar. Explosions and Accidents. stated (Quarterly Journal of Science, &c. No. XIV.), that one cubic foot of oil-gas will yield as much light as four of coal-gas; but, in another part of the same article, that the proportion is only five to nine. Mr Brande (Annals of Philosophy, December 1819) gives one to two as the proportional value of the two gases our own experiments give seven to thirteen. Much discrepancy may arise from the way in which such experiments are conducted: an argand burner, which will, when burning coal-gas, give, with the greatest advantage, a light equal to any number of candles, should, when used with oil-gas, be adjusted to emit a considerably greater quantity of light, in order to burn that gas in the most economical manner. There is always a portion of blue or dark coloured flame adjoining the burner; and to make the comparison fair, this ought to bear an equal proportion to the white flame in both cases; and though some attention was paid to this circumstance in making our experiments, we have little difficulty in believing that the result would have been somewhat more favourable to the oil-gas, had the proportions of white and blue flame been more accurately adhered to; and we therefore incline to consider Mr Brande's numbers of one to two as the most correct. The volume of gas which a given quantity of whale-oil yields has been variously stated, at from 80 to 110 cubic feet per gallon, and the quality of the oil, and mode of distillation, may partly account for the difference. We have not been able to obtain more than 95 to 98; but as some waste took place, in the portion which was volatilized not being wholly condensed and collected, it is probable that 100 may be taken as the number of cubic feet which one wine gallon of good whale-oil will produce. Gas from Coal Tar. Attempts have been made to decompose coal tar in order to obtain the gaseous products; and this may be effected without much difficulty, by an apparatus nearly similar to that used for decomposing oil, and by other means. But it does not appear from the experiments which have been made, that the gas produced is well fitted for the purposes of illumination; probably from a great quantity of pure hydrogen being mixed with the carbureted hydrogen gas formed; or, if Mr Brande's theory of the non existence of the latter gas be correct (Annals of Philosophy, December 1819), because the olefiant gas occurs in extremely minute quantities, compared with the quantity generated during the distillation of coal. When atmospheric air is mixed with about oneeighth part of its bulk of coal gas, and set on fire, it explodes; and, if in a confined situation, may do serious mischief. Accidents have occurred from these explosions, which originate in ignorance, mischief, or carelessness. The offensive odour emitted both by oil and coal gases unburnt, is a very suffi cient warning of their escape; and the propriety of Gas-Light. having every part of a gas apparatus perfectly tight, and free from leaks, is a matter of importance, not only as regarding safety and the prevention of this nuisance, but also the actual waste and loss of a valuable commodity. A leak from a hole one-twentieth of an inch diameter would, under the usual pressure, in the course of one year, waste coal gas to the value of L. 10 and upwards; and, supposing it to be emitting gas into a chamber of ten feet cube, it would require from two to three days to render the air of it explosive, and this only on the supposition that the apartment was nearly air-tight. Any ordinary escape of gas into a room, having a door, window, and fire-place, where a circulation of air is constantly going on, could never cause an explosion, though explosions have occurred, from its getting, in the first instance, into confined adjoining places, as closets, cup-boards, arched vaults, or the like. In these situations, when the smell of gas is perceived, ventilation should be resorted to, by opening the doors, &c. and lights should be kept away from them, until the smell ceases to be offensive. Economy of Gas-Lights. We now come to treat of the expence of light ob- Economy of tained from coal and oil gases, and their comparative Gas-Lights. cost, compared with that from oil and tallow, as commonly consumed in lamps and candles. The fluctuations of price to which these commodities are liable, and the varying expence in different places of buildings, and other things required in forming a gas-work, must, of course, render any statement of comparison that can be given inappli cable to the forming of any other than a very general result. The expence of such an apparatus, as is represented in Plate LXXXIV. may be taken as follows: 5,200 Twenty-one retorts, with all their appendages, tarvault, condensing and purifying apparatus, and buildings, belonging to the same, L. 5,500 Two gasometers, with their cisterns, and all apparatus, and buildings, The cost of the main pipes, with their stopvalves, water-receivers, &c. for distributing the gas, must depend entirely upon circumstances which cannot be considered here. In lighting towns, the amount has, in some cases, equalled, or somewhat exceeded that of the rest of the apparatus. Say then, Total expence, 10,300 L. 21,000 This apparatus will be capable of supplying about' 50,000 cubic feet of gas daily, using sixteen or seventeen of the retorts; the remainder being kept as a reserve in case of accidents to the others from cracks, burning, or wearing out. cracks, burning, or wearing out. And though such a consumption of gas should be necessary in the depth of winter, yet it will be found, that, upon an average for the year, a daily supply of about half the quantity will suffice in the way in which it is Gas-Lights generally consumed in lighting towns. This appa- To procure this quantity, 48 cwt. of cannel or coal of the above, and at half the price, Two and a half per cent. on the amount of Ten per cent. on the amount of the other Annual expenditure, In the above calculation for the expence of coal gas, Gas-Lights. no mention is made of the coke, tar, oils, and ammonia produced. The value of the coke depends much upon the nature of the coal employed; that obtained from such as the Newcastle coal answers well for house fires, drying kilns, stoves, &c.; but the Cannel coal, which is used for making gas to a great extent in many parts of the kingdom, gives a very inferior coke, of frequently not more than 1-5th to 1-6th the value of the coal which produced it. The tar, when boiled and mixed with drying oil and other substances, forms a paint which may be used for common purposes; it may also be converted into 230 pitch, and by burning it in close vessels, a species of lamp black is produced. On the whole, this and 260 the other liquid products have, however, not been considered as of much value, and the getting rid of them and of the refuse lime, which has been used in purifying the gas, is often attended with an expence which their own value, and that of the charcoal, will not more than compensate. 220 270 1,090 1,070 L. 4,020 Which amounts to L. 11 per day as the cost of 1000 =2d. barely. Though the expence of lighting by gas from oil appears, on a large scale, not to be much less than double that of coal gas, the same great disproportion will not altogether hold for very limited quantities of light, where the charge for an attendant forms a considerable part of the current expenditure. A coal gas apparatus, however small, will, when in work, require the almost constant attendance of a person to manage the fire, to charge and discharge the retort, to renew the lime or other substance used for purification, and to remove that which has done its office, also to empty the tar reservoir, &c. In the other apparatus, when the oil reservoir is filled and once set to work, it requires no other attendance for a number of hours, than the keeping of the fire in order; and the production of gas can L. 3,709 be continued at pleasure, or stopped by the mere turning of a cock, and the nuisances accompanying the formation and removal of tar, ammoniacal liquor, and lime refuse, are entirely avoided. An apparatus capable of supplying an equal quan- Retorts with all their apparatus, condensing Gasometers, &c. of half the capacity of the Main pipes, &c. the length supposed the 3,500 7,700 L. 14,900 Total, To produce this, 125 gallons of oil are ne- Management, wages, and sundry charges, 2 per cent. on main pipes, &c. 10 per cent. on the other parts, Annual expenditure, An argand oil lamp with a burner three-fourths of an inch diameter, we have found to consume 406 grains of the best spermaceti oil in one hour, when giving the light of 3 candles of the size above specified. Five thousand grains of oil will, therefore, give the same quantity of light that 1 lb. of tallow does, and valuing it at 5s. 6d. per gallon, the cost will be, with an allowance for wicks and trouble of trimming, about 63d. The comparative expence of light from the different substances mentioned below will then be as follows: Valuing the quantity which 1 lb. of tallow L. 5,780 220 3. d.. 820 100 1 0 190 720 An equal quantity of light from spermaceti 0 61 0 4/ L. 7,830 Or about 41d. for a light equal to what 1 lb. of tal- A ditto ditto from coal gas, It would have been desirable to have been able to give a comparative table of the actual charges made for supplying gas-lights in some of the principal towns of the kingdom; but unless some stand GENOVESI (ANTHONY), an eminent Italian Writer, was born on the 1st of November 1712, at Castiglione, near Salerno, in the kingdom of Naples. From his earliest years he showed an uncommon capacity; but after receiving such education as his native village could afford, his father obliged him to devote himself to the study of scholastic theology, with a view to the ecclesiastical profession. In a short time he distinguished himself as a proficient in dialectics; but having formed an attachment to a young woman, he was on the point of sacrificing to her all his professional prospects, when his father, who had obtained a knowledge of the circumstance, removed him to another village, where he found a priest who diverted his attention to different objects. Having been afterwards excommunicated by the Archbishop of Conza for acting a part in a comedy, he returned to Castiglione; where, having found his mistress married, he reassumed the cassock, and took priest's orders at Salerno in 1736. Here he soon distinguished himself so much by his talents and knowledge, that the Archbishop of this town confided to him the Chair of Eloquence. At this period Genovesi was a mere school theologian; but a friend of his, a young ecclesiastic, now made him aware, that there were sources of knowledge beyond the scholastic sphere, more extensive, more interesting, and more real, than those to which he had hitherto applied. Genovesi entered into this new intellectual world by the perusal of some romances; from these he proceeded to the study of history; and stepping from one subject to another, he finally applied himself to the study of modern philosophy, and read with attention the works of Leibnitz and Locke. In the hope of acquiring still farther information, he repaired to the capital; and as he did not possess the necessary means of maintaining himself there, he resolved to exercise the profession of an advocate; but becoming disgusted with the details of practice, he soon sacrificed his hopes of fortune to the pleasures of study. He improved his knowledge of the Greek, and of several of the modern languages; attended all the most celebrated professors of the University of Naples; and soon perceived the imperfections of the existing system of public instruction. Notwithstanding the progress which philosophy had made in other countries, the kingdom of Naples was, at that period, in a state almost retrograde, or, at least, stationary. Genovesi felt this, and he resolved to accomplish certain reforms in the system of education, with a view to the amelioration of the condition of his countrymen. None ever succeeded better in this generous design. Although there existed at Naples a University, celebrated for the learning of several of its Professors, the pupils had long been accustomed to carry on their studies in private schools. Genovesi having conceived the design of opening one of these seminaries, he procured the appointment of extraordinary Professor of Metaphysics in the University, in order that he might appear before the public in a known character. He had formed peculiar methods of his own in all the faculties which constitute the philosophical course; and his first Essays induced him to publish his Elements of Metaphysics, of which the first volume appeared in 1743; and afterwards, in 1745, his System of Logic. In these two works, he made ample use of the doctrines of Bacon, Descartes, Leibnitz, and Locke; and, having substituted philosophical doubt for implicit belief; the observation of nature for the speculations of the schools, and reason for authority,— this was sufficient to cause him to be denounced as an infidel, or at least as an irreligious person, by those who still adhered to the scholastic methods. He would probably have fallen a sacrifice to these prejudices, had he not been supported by Galiani, Archbishop of Tarentum, Grand Almoner of the King, and Grand Master of the University; but, notwithstanding this protection, he experienced some trouble and difficulty in obtaining the professorship of Moral Philosophy; and he was disappointed in an attempt to procure the chair of Theology. The unjust and obstinate hostility which he suffered on account of his theological works diverted him, for some time, from this dangerous path of inquiry, and brought him back to that of philosophy. He published a continuation of his Elements of Metaphysics, but, with every new volume he continued to experience the censures and opposition of the partizans of the scholastic routine. Among these were the Cardinal Spinelli, Archbishop of Naples, and an Abbé Magli, whom Genovesi covered with ridicule in his work entitled Lettere a un Amico Provinciale. In spite of these continual jarrings, Genovesi obtained the approbation and esteem of Pope Benedict XIV., of several Cardinals, and of most of the learned men who at that period flourished in Italy. Of this number was Intieri, a Florentine, who having spent a long time at Naples, became much attached to that country. This man, as distinguished for his philanthropical qualities, as for the extent and solidity of his acquirements, was still more estimable on account of the use which he made of his fortune. It is to him that Italy is indebted for her first Chair of Political Economy; he founded it, at his own expence, with the sanction of government, in the University of Naples, under three conditions, viz. that the lectures should be given in |