The salary which would thus be raised would be sufficient to induce many an individual, sufficiently qualified for a Lecturer, to compete for the office. The Divinity-Hall is itself an emporium of talent, fated to go down to oblivion unknown, for want of opportunities to call it into exertion. There is, in short, many an aspirant after a church-but who, unfortunately, will never get oneperfectly ready, and, I doubt not, able enough to fill a Lecturer's chair in a provincial town. It would be desirable, it is true, to obtain Lecturers combining scientific with practical knowledge; but it would be needless, I fear, to hope that persons so qualified could be found willing to undertake such a charge for so small a salary. But it will be observed, that the salary above counted upon is guessed at the very minimum.

From an actual experiment that has been made in a town in the south of Scotland, (the inhabitants of which are deserving of much credit, for the desire to diffuse useful knowledge which they have evinced,) I would not be afraid of an attempt to establish such institutions as those I have suggested failing on account of a paucity of pecuniary means. In Hawick, a School of Arts was begun last summer, and Mr Wilson of the School of Arts in Edinburgh was appointed Lecturer. The voluntary contributions of the inhabitants, aided by a handsome donation from a benevolent and very excellent individual* in the neighbourhood, amounted to a sum sufficient to purchase a small assortment of apparatus, and to afford Mr Wilson a remuneration, with which he was at least satisfied. Now, Hawick is but a small town, containing, I understand, only about 5000 inhabitants. But if it can alone support a School of Arts, there is surely room to infer, with considerable probability of being pretty correct in the inference, that were Hawick to unite with some of the neighbouring towns-with Jedburgh and Kelso, for instance-a School of Arts upon a more extensive, and probably also upon a much more useful plan, might be erected in the first-mentioned town; and at

the same time schools of the same nature, equally extensive and efficient, might be established in the other two towns. In the same way, Schools of Arts might be formed in all the towns in Scotland-dividing them into districts of three or four towns each, as in the case above supposed.

An attempt is now making to form a scientific institution in Dundee, similar to that of Edinburgh; but from what I have heard of the plans proposed by the sçavans of Dundee, I think, with all deference to their views, that they are attempting too much at first. The institution in Dundee, from what I have heard of it, is meant to be adapted to the instruction of mechanics exclusively. But for more reasons than one, this is doubtful, if not evidently bad policy; for, in the first place, were people of every description invited and encouraged to become students, the funds would be thereby so much increased, the whole body of the institution would be strengthened, and its stability rendered doubly secure. In the next place, students, not actually mechanics or tradesmen, would have an opportunity of being instructed in matters of useful knowledge, of which they might otherwise remain as ignorant as the most illiterate mechanic. And, lastly, the attendance of genteel lads, and even school-boys advanced in their education, would render the institution many degrees more respectable, and command a greater decorum in the class. One of the most pleasing peculiarities, indeed, which strike a visitor in the Edinburgh School of Arts, is the remarkable decency in appearance and neatness in the dress of almost every student in it; and much of this may be attributed, I doubt not, to the circumstance that genteel people send their sons to it as students, and even a certain number of subscribers are permitted to be regular auditors. But the first is the most important consideration in reference to a School of Arts in a country town, where it would be necessary to make every exertion in order to raise pecuniary means. In every view, however, it would be necessary,

and at all events most advisable, to use every means for securing an attendance of miscellaneous students in a provincial institution.

The last remark with which I shall at present trouble you is, that such institutions are so evidently advantageous to the country in general, and so conducive to the improvement .of young tradesmen, not only in a secular point of view, but also in regard to their morals, that they are deserving in an eminent degree of parliamentary encouragement. It is not when the mechanic has his tools in his hand, or when the tradesman sits on his loom, that he ruins his own morals and those of others, by debauchery and seduction. The few hours which he ought to spend in relaxation, or devote to study after retiring from the workshop, are set apart for these purposes; and instead of becoming useful to society, therefore, he too often becomes in it a moral pest. But the prevention of these evils is only consequent upon such institutions as Schools of Arts. Indeed I would not urge this as a reason for inducing Parliament to patronize them. I would rather point out the palpable good that would accrue to the nation by training up a body of scientific mechanics and operatives to carry our manufactures to still greater perfection; and at the same time, nothing could so materially contribute to raise their moral grade in society. There is

something salutary, indeed, to the feelings of a mechanic, and ameliorating to his whole character in the mere abstract, though very influential circumstance, of his undergoing a course of education so nearly resembling that which is followed by those of the learned professions in seminaries and colleges.

Though there is something moral, certainly, in the idea of establishing throughout the country such secondary colleges, if I may so designate them, upon a plan so systematic as that which I have ventured to suggest, yet the scheme is not destitute, in my estimation at least, of something approaching to grandeur; while there appears to be nothing in it at all extravagant, or even impracticable. The practical result, however, not the mere honour, which such institutions would reflect upon the country, is what ought, in such a case as the present, to be chiefly counted upon; and we have pretty sure data before us, from which to infer, that that result would be of a nature incalculably profitable and advantageous to the nation. I should think, therefore, that were the matter fairly laid before Parliament, a grant of a few thousands would not be grudged, to establish these institutions upon a more enlarged and useful plan than any that could be adopted without such aid.

Nov. 4, 1824.

PHILALETHICUS.

Illuminating Powers and Comparative

Prices of Gas from Coal and Oil.

THE attention of the Directors of the Edinburgh Gas Light Company was early directed to the lighting from Oil Gas,

with a view to ascertain how far it might at any future period, become prudent to adopt its manufacture in the Establishment under their charge, either in conjunction with that of Coal Gas, or by itself, to the exclusion of the latter; but

they were soon convinced that there could be no competition of Oil with Coal Gas, in point of economy. As a profitable adventure, therefore, they gave up all thoughts of recommending it to their constituents.

Since the formation of a most respectable Company in our city for supplying it with Oil Gas, much has been said and written on the comparative illuminating power of Oil and Coal Gases; and the Directors naturally became most desirous, by actual experiments, to arrive at the truth of the various discrepant statements, tending (many of them) most materially to undervalue the qualities of Coal Gas, and to place the superiority of Oil Gas beyond all possible question.

At the commencement of last winter, the Directors, therefore, earnestly requested the favour of Professor Leslie's undertaking a series of such experiments, solely for their private information. But the very incorrect and unfounded assertions that are continued to be made on this subject, would render the Directors chargeable with a want of duty to the Proprietors of their Company and to the public, if they refrained from publishing the following letter, which they received the other day from that learned Professor, confirming most explicitly the opinion which the Directors had formed on this subject.

"To the Directors of the Edinburgh Gus-Light Company.

Edinburgh, 19th July 1824.

"GENTLEMEN,

"The various discrepant accounts, and the confident assertions, repeated, I suspect, without due examination, concerning the relative advantages of the Coal and the Oil Gas, made me desirous of instituting an inquiry into the subject, with more precise and accurate means of investigation than had been generally employed. Your invitation last winter to make experiments on this important subject prompted me to defer this research no longer; but as I projected several changes and modifications in the instruments to be used, I could not conveniently commence the operations till within these few weeks. I am now engaged in the prosecution of an extensive series of such experiments, which promise all the information that could be desired.

"Though I have had time to explore a part only of the subject, yet the results, however different from the common averments, are consistent and satisfactory, and may be deemed important. I therefore think it right to make a report at this stage of the inquiry, but shall

VOL. XV.

confine my remarks to two points; 1st, the comparative Density of the Gases; and, 2d, their relative powers of illumination.

"First, The Density of your CoalGas commonly does not much exceed six-tenths of that of atmospheric air: when I began the operations, its density was only 593; but it was afterwards 618, and is now 623. In winter I once found it to be 680, and at another time as high as 700, though it was oftener at 600. The variation, I presume, sel'dom exceeds the eighth part.

"A small quantity of Oil Gas, procured for the experiments, I found to have the specific gravity of only 674, not greater, indeed, than that of your Coal Gas, when made of the best coal. The Oil Gas, however, furnished by Mr Milne, manufactured on a small scale, and apparently with great care, at his works, was materially denser, being as high as 943, though, on a former occasion, I found it to be only 810.

I

"If we assume in round numbers the density of Coal and Oil Gas to be six and nine-tenths of that of fatmospheric air, it is easy to compute, that, under the pressure of half an inch of water, the quantities discharged from the burner No. I, of the Oil Gas, which contains ten holes, each having the of an inch in diameter, would be respectively 43 and 38 cubic feet. The quantities actually consumed, however, are only about the halves of these measures, because the aperture is always contracted by partly shutting the cock, to bring the flame to the same standard height. When the flame is thus regulated, I find the consumption of the same Gas, and with the same burner, always the same, whatever may be the load placed on the Gasometer. For instance, after increasing the load four times, and consequently doubling the velocity of discharge, yet, on adjusting the cock, so as to reduce the flame to its former height, the expenditure of the Gas was not altered.

"Second, The illuminating powers of the two Gases were measured with great accuracy, by the application of my Photometer, which I had somewhat modified, to exclude every irregular influence of heat. The indications were steady, and easily noted, nor could the judgment of the observer be liable, as in other cases, to any sort of bias or indecision. It hence appears to be ascertained, that with the same burner the powers of illumination of different Gases, and of the same Gas in different states, are very nearly proportional to their densities. The same weight of Gas of any kind gives out the same

4 Z

quantity of light; but if equal bulks be taken, the illuminating powers follow the ratio of their densities. But the quantity of light emitted is not uniformly proportioned to the measure of the Gas expended. A certain burner, for instance, was observed to produce double the illuminating effect, though it consumed only one-half more of either species of Gas. With No. 1, of the Oil Gas burner, the relative illumination of Mr Milne's Oil Gas to that of your Coal Gas, was found to be as six to five. But a cubic foot of the foriner lasted thirty-eight minutes, while a cubic foot of the Coal Gas was spent in thirty minutes and a half. The relative volumes consumed were hence, in the space of an hour, 1.58 and 1.97, or in the ratio of four to five. Wherefore, while five cubic feet of Coal Gas give five degrees of light, four cubic feet of the best Oil Gas give six degrees; that is, for equal volumes, the illuminating power of the Oil to the Coal Gas is as three to two. The same conclusion was obtained on passing those several Gases successively through the Argand Coal Gas burner No. 2.

"Thus the illumination of Oil Gas is actually less than the half of what has been currently asserted.

"I have the honour to be,
"GENTLEMEN,
"Your most obedient servant,
"JOHN LESLIE."

From the ratio of illuminating power, which Professor Leslie has thus found to subsist between Oil and Coal Gas, it follows that 1000 cubic feet of the former are equal to 1500 cubic feet of the latter, giving out the same quantity of light, and being in every respect equal in value.

The lowest price at which Oil Gas has yet been sold is 40s. per 1000 cubic feet, and that of Coal Gas in Edinburgh is 12s. per 1000 cubic feet.

Thus the price of 1000 cubic feet of Oil Gas is £.2 0 0

And the price of 1500 cubic feet of Coal Gas (affording the same degree of light) is

Hence, there is a saving, by

the use of Coal Gas, of

0 18 0

£.1 2 0

Or, in other words, the same quantity of light which, when produced from Oil Gas, will cost £.20, will cost only £.9 when produced from Coal Gas.

By order of the Governor and Directors, ALEX. KIDD, Sec. Edinburgh Gas-Light Company's Office, 26th July, 1814.

Illuminating powers of Gas from Coal und Oil.

To the Proprietors of the Edinburgh Oil Gas Light Company.

The Directors of the Oil Gas Light Company, upon observing a widely-circulated statement, by the Managers of the Edinburgh Gas Light Company, transmitting the opinion of Professor Leslie on the relative illuminating power of the Coal and the Oil Gas, found, that their duty to their constituents and to the public required a minute and careful examination of the results pointed out by the learned Professor;-such results being not only prejudicial to the undertaking of the Oil Gas Company, but, in so far as the Directors know, contradictory of all that has hitherto been stated upon the subject. The Directors saw, at the same time, the propriety, from respect to the high scientific character of Mr Leslie, and still more in justice to their constituents and to their own characters, of proceeding with the most scrupulous care, in their investigation of this important subject.

Two modes occurred to the Directors of proceeding in this inquiry: First, By philosophical experiments, conducted by persons of scientific eminence: Secondly, By ascertaining how the merits of the two modes of lighting have borne comparisons with each other, where the experiment was conducted on an extensive and practical scale, by rival Companies. They have now the honour to lay before their constituents the result of their inquiries upon both points, with the reports on which those results are founded; and have, at the same time, the pleasure to being in every respect highly satisfactory. congratulate the Proprietors upon these

In inviting persons of science to assist them in investigating this subject, the Directors of the Edinburgh Oil Gas Light Company have been particularly careful to avoid calling in the assistance of any of those interested in the Company's prosperity, as shareholders, or otherwise ;— because, such must be, in some measure, regarded as parties interested ;—and, because the most acute minds, in the prosecution of a train of experiments in which their own credit and interest are less or more concerned, have been frequently found to arrive at conclusions rather corresponding to previously-conceived wishes and opinions, than to accurate deduction from fact, on philosophical principle. The Gentlemen of science to whom the Directors submitted Mr Leslie's statements, which aver the superiority of the Gas Light from Coal, to that formed from Oil, are, Dr Turner, Lecturer on Chemistry in this city, and Dr Christison, Professor

of Medical Jurisprudence in the University of Edinburgh ;-Gentlemen, whose competence to the task of investigation cannot be disputed; and the Directors had also a separate communication to the same effect, with the celebrated Dr Brewster. None of these gentlemen are proprietors of the Oil Gas Light Company; and Dr Brewster is interested as a shareholder in that of Coal Gas; so that his prejudices, (supposing him to be capable of entertaining any,) must have been opposite to the result, to which it will presently be seen he was conducted by his experiments.

It is the unanimous opinion of these learned Gentlemen, (concurring with that of almost every chemist who had previous ly given attention to the subject,) that, according to the most accurate experiments hitherto performed, the proportion of the Oil Gas Light, in comparison to that of Coal, varies, between two and a half, to three and a half, to one ;-being the proportion which the Directors of the Oil Gas Light Company have always announced to the public, instead of being only as three to two, the proportion stated by Mr Leslie. The same eminent chemists have stated, in different terms, but to the same effect, that Mr Leslie's apparent miscalculations have arisen in this instance from his trusting to an instrument of his own device or adoption, termed a Photometer, affected in a much greater degree by heat than by light, and thus rendered utterly unfit for measuring light alone. It is true that Mr Leslie announced that this instrument was "somewhat modified," for the purpose of conducting this investigation; but the nature of the alteration is no where explained; and that which has been surmised as the process is, in the opinion of Drs Turner and Christison, totally inadequate to render the Photometer an accurate mode of measuring light. Yet it is upon the results obtained by this instrument alone, said to have been " some. what modified," to render it applicable to a purpose for which it is quite unsuitable, that Mr Leslie's isolated opinion -respectable as the Directors admit it to be-is opposed, in solitary dignity, to that of almost every other chemist who has investigated the subject. It has always been objected to the Coal Gas, that it emits, during consumption, an inconvenient degree of heat; and if the Photometer, faithful as an indicator of heat, confirms this fact, it is no more than has been always known and insisted upon, as rendering it very unfit for domestic purposes, and inferior, in proportion, to that procured from Oil.

The Directors have to solicit the attention of the proprietors to the important evidence supplied by the Letter of Mr Pollock, Secretary to the Oil Gas Company of Dublin, which, supported by documents of the highest respectability, shows plainly the superiority of Oil Gas, when in opposition, not to one, but to two Coal Gas Companies. This, it may be observed, depends upon no train of experiments, conducted in the solitude of a chemist's laboratory, by an instrument confessedly inaccurate, until said to be adapted to an investigation for which it was not suitable, by some slight modification, which remains unexplained; but, on the contrary, rests upon the opinion formed by the public at large, where a fair opportunity had been afforded them, of judging for themselves, and adopting that species of light which should be found most brilliant, wholesome, and economical.

The Directors of the Edinburgh Oil Gas Light Company regret the necessity of thus replying to the charge pretty directly launched against them, of having circulated discrepant statements," and "confident assertions," suspected to be made without due examination, respecting the relative advantages of the Oil and Coal Gas. They indeed asserted, upon the authority of Brande, Phillips, Faraday, Henry, Hawes, Ricardo, Dewey, and other competent judges, that the powers of the Oil Gas, compared to the Coal Gas, are from two and a half, to three and a half, to one, according to the qua lity of the Gases. In this, the opinions so formed have been contradicted on the authority of one instrument, which is better calculated to measure heat than light, and indicates total darkness, and is insensible to the light of four wax candles, when removed at such a distance, that their heat does not affect it. They beg leave to appeal from so incompetent and inconsistent an authority, to the actual experience of the public, who, if not willing to decide, when men of eminence disagree, will speedily, like the citizens of Dublin, have a more satisfactory opportunity of deciding the question by their own experience.

In conclusion, the Directors, without entering more into detail, have no hesitation in stating their conviction, that the price of Oil Gas, besides the other advantages attending it, will be found, upon trial, not to exceed the price of Gas produced from Coal.

By order of the Directors, RODK. MACKENZIE, Sec, Edinburgh, 6th October, 1824.