was the result, when, as happened several times, the candles were allowed to burn a little too long. On the evening of the fete day, a very pleasing effect was produced by the simultaneous lighting of two long rows of candles, extending through the trees along the entire length of the Gardens of the Tuileries, suggesting a wish for the better success of the endeavors that have lately been made to light and extinguish our own gas lamps, by the same agency. Except, however, for special objects, such as the illumination of fountains and cascades, gas is much to be preferred for the purposes of a general illumination, its superior divisibility rendering it peculiarly adapted for the production of artistic effect. The prominent characteristic of the electric light is, of course, its concentration, but this, which probably constitutes its chief value as an out-door illuminant, is a fatal obstacle in the way of its general adoption, and hence, it is only natural that its advocates should endeavor to overcome this by attempting a more minute subdivision of the electric current than has yet been acheived. We were shown, by M. Jablochkoff, at the Pavilion of the Electric Light Company, in the Exhibition, an arrangement by which, he has succeeded in producing, at will, two ordinary or four smaller candles from the same source; but the cumbrous nature of the apparatus employed, precludes the possibility of its possessing any immediate practical value. With regard to the question of comparative cost, it is clearly not necessary to invest the fact of the employment of the electric light in Paris during this exhibition period, with any special significance, since it may be fairly assumed that, under the circumstances, other considerations would be allowed to have at least equal weight; and the fact that, in the principal thoroughfares lighted by this method, "Coal gas resumes its sway," as a recent writer to the Times expressed it, shortly after midnight, shows pretty clearly that the Municipality have not yet made up their minds to abandon its use. In the Avenue de l'Opera, and Place of that name, to which this observation more particularly applies, 180 ordinary gas lamps are every evening temporarily displaced by 30 electric candles, being in the proportion of one to six; and as the Municipality pay for the candles at the rate of 1 franc 25 centimes, or about Is. per hour, each, while gas for six burners would cost for the same period, at 7s. per 1,000 cubic feet, which is about the price of gas in Paris, a little less than 3d., it is apparent that the candles are a luxury in which it is quite possible too freely to indulge. It is, however, only right to state that the light given by them is much superior to that afforded by the gas lamps, used in the above proportion; but if the comparison be made upon equal terms, it will still be found to be very much in favor of gas. For instance, if we assume that the light given by one electric candle be twice as much as what I conceive to be a fair estimate, viz., 200 candles, then the comparison will be between the light of 400 candles distributed from one focus, and costing Is. per hour, including attendance, wear and tear, and, it is to be presumed, promoter's profit-and 30 gas lamps distributing their light, as a matter of course, over a far greater area. The latter would cost For gas, at 3s., 150 cu. ft. per hour To which add, for lighting, cleaning and ex- Total 5.4d 1.08 6.48 Or, say 61⁄2d., which, deducted from the Is., as above, leaves a balance of 51⁄2d. in favor of the gas, in addition to which there has to be taken into account the undoubted economy resulting from the far greater area which would be illuminated by the latter. It will be apparent from the foregoing that, while the electric light possesses certain advantages which may procure for it a limited amount of favor for special purposes, these advantages are accompanied by such serious drawbacks as to render it unsuitable for general employment; so that although in some particulars, as in the cost of the "candle" proper, it would seem to be a matter of no great difficulty to effect improvements, suggesting the desirability of watchfulness over any progress that may be reported, there appear at present to be no grounds for believing that coal gas is likely to any extent to suffer from the rivalry with which it has for some time past been threatened. CHARLES HUNT, Engineer. WINDSOR STREET, August 5th, 1878. Since the above was written I have been favored with a sight of a copy of an estimate, given by M. Jablochkoff to the managers of a club house in Paris, for the supply of apparatus complete, including magneto-electric machine, five or six horsepower engine and boiler, lanterns, wires, and every other requisite, fixed ready for use, the cost for four candles being 11,623 frs. 50 c., or nearly £465. He further estimates the cost of maintaining the four lights, including the candles, attendance and fuel for engine, at 3 frs. 54 c. per hour, or 2s. 10d. English. MR. HARBISON-While upon the subject of electric light I will state that some of the members understood Mr. Nettleton to say that the light, as used by Mr. Wallace, was without a return wire. If he is here I would be glad if he would be kind enough to repeat his statement in that respect. MR. C. H. NETTLETON—As I understand him, and I think I am correct, the wire is run from the machine around the shop, and back to the machine again. In that sense it is a return wire. But whenever he wishes to put in a lignt, or a candle, he cuts the wire and inserts the candle. His machines are of different sizes. He has them from two lights each, up to eight lights, and, I think, twelve lights. But those candles are all on one wire; and, furthermore, he has it so arranged that he can put out one candle, and all the rest will remain just as well as if all were burning. MR. HARBISON—In regard to the subject of testing the temperature of retorts; in addition to what Captain Dresser said, allusion was made to the fact that some experiments had been made by Mr. Greenough, of Boston. Mr. Greenough gave us, at the New England meeting, a very interesting report of some experiments that he had made; and I think it will be of great interest to those gentlemen who were not in Boston if he will repeat that statement here, and give us the results of the experiments that he made in regard to the temperature of the retorts during the burning out of the charge. MR. WOOD-Before we come to that I would like to inquire of Captain Dresser one thing. If I understand him, he says that there are four or five candles placed in one lamp, and that these burn for five or six hours. CAPTAIN DRESSER-Yes; burning one at a time. They burn one and then light another. They are not all lighted at once. Each one of these burns about an hour or an hour and a quarter; and, as there are four of them, each lamp will last about five hours. A MEMBER Did you test the heat of the electric light? CAPTAIN DRESSER-I will state that, so far as the lights in the Exposition were concerned, they were in such a shape that we could not get at that. But the Chartered Company, of London, have bought an electric machine, and a series of experiments are being made, by Mr. Sugg and Mr. Evans, to determine all these points. I was present with Mr. Sugg several times when experiments were being made, and we found that there was a great deal of heat in these lights. There must, of necessity, be a great deal of heat because it is this intensely heated carbon point that gives the light. THE PRESIDENT-Will Mr. M. S. Greenough explain his experiments in accordance with Mr. Harbison's request? MR. GREENOUGH-I do not think there is the least difficulty in obtaining a tolerably accurate estimate of the heat of your retort. The method which we adopted in the experiments made in our works is the one that has been in use for many years in France, and, not only in France, but in various parts of the Continent, though not, I think, in England. It is simply an application of the principle of specific heat. It is, of course, known to every gentleman here that a given weight of one material will be more affected by a certain quantity of heat than an equal weight of another material. In the case before us, for example, if you take a certain weight of iron, say, five lbs, and leave it in the retort until it has been thoroughly heated, and then immerse that iron in a given weight of water, say, 40 lbs., the temperature of which has been previously taken, it is very easy to calculate what the temperature of the iron must have been when it was immersed, by noting the increased temperature of the water afterwards. You may not get, perhaps, within 50° of the temperature; but I have no hesitation in affirming my belief that, in the retorts I have experimented with, we have came as near as that. It is part of the ordinary operation of all our works, to thus test the temperature of any retort of the heat of which there is any question. I think gentlemen who have not made the experiment, and who are running charges, as they do in some works, of five or six hours duration, would be very much astonished to find how great is the reduction of temperature in the retort that actually takes place after the charge has been put in. It is very large, even for comparatively light four-hour charges. Take, for instance, an ordinary sized retort, and put into it a charge of 225 pounds of coal. The temperature of the retort before it was put in would be probably about 2300°; after the coal has been put in it will be some time before it is heated to a thousand degrees. At the end of an hour it will hardly get over 1400°. The heavier the charge put in, of course, the more the temperature will fall in the retort. If some ingenious plan could be devised similar in principle to Clegg's revolving web retort, by which only a small amount, say, 50 lbs. of coal, should be exposed to the action of the retort, at one time, we should all be surprised, I think, at the results obtained. On motion, adjourned until ten o'clock to-morrow. THIRD DAY. The Association met at 10 A. M., pursuant to adjournment, and was called to order by the President. On motion, the reading of the minutes of the proceedings of yesterday's meeting was dispensed with. MR. NEAL-I move that the thanks of the Association be tendered to Prof. Morton for the instructive and interesting lecture delivered by him in the presence of this Association, and others, last evening, at the Stevens Institute. Carried. The Executive Committee then made the following report: The Executive Committee offer the following recommendations |