repeating at present, as I have not extended my experiments on them sufficiently. If what I have stated should be sufficiently interesting, and at the same time compatible with the nature of your publication, I will thank you to give it an insertion. Philadelphia, July 27, 1814. ARTICLE III. Experiments on the Draught of Carriages. Mr. Bryan presented the following Report from the Committee of Mechanics and Natural Philosophy of the Dublin Society : Report of the Committee of Mechanics and Natural Philosophy of the Dublin Society. On Saturday, the 22d of April, your Committee attended in the yard of Leinster House, when the following experiments were pub licly made by Mr. Edgeworth : Experiment I. Two furniture carts were placed at one end of the yard, which was paved in the ordinary manner. They were both constructed upon grasshopper springs; one of them was painted yellow, the other green. These carriages were pulled forward by the apparatus invented by Mr. Edgeworth, which consists of a two-wheeled carriage, drawn by one or two horses, upon which a wheel or pully, of nearly eight feet diameter, is so placed as to turn freely in an horizontal direction. A rope, passing round this wheel or pulley, is attached by its ends to the carriages that are to be compared ; and, as the apparatus is drawn forward, the two carriages must follow, and that which goes the easiest will get foremost. This apparatus was drawn at a moderate pace by two horses, and that carriage which ran the lightest and easiest was loaded till the other kept pace with it. Five cwt. was then placed upon each. The springs of the yellow carriage were prevented from acting by blocks of wood interposed between the springs and the body of the carriage. The green carriage, the springs of which were allowed to act, was now loaded with 14 cwt. additional weight, making a total of 64 cwt.; and the green carriage so loaded was found to get before the yellow carriage, the weight on which amounted to only 5 cwt. By this experiment it appeared that the carriage upon springs had an advantage over that without springs of one-fourth of the weight that was laid upon it. Experiment II. Two post-chaises, weighing each 12 cwt. 7 lb. one of them painted black, the other white, were next compared; the perch of the black one was moveable, so that it could be lengthened or shortened at pleasure. When their perches were of equal length, viz. of seven feet six inches, the carriages were compared previous to these experiments, and their draft was equalized by an addition of weight to that which ran the lightest. The perch of the black carriage was now lengthened to ten feet three inches. The carriages were each of them loaded with 2 cwt. They now nearly kept pace with each other, the one with the long perch appearing to have rather the advantage. Experiment III. The load, which in the former experiments was placed in the bottom of the white carriage, was now placed in an imperial on the top. The removal of the weight four feet higher from the ground did not promote the progress of the carriage, which did not yet keep pace with the black carriage. Experiment IV. Two similar Scotch drays, one of them painted blue, and the other red, were now compared. They had been brought to an equal weight; and the blue carriage was supported upon wooden springs, consisting of two pieces of elastic timber, connected with the bottom of the dray by iron shackles; each dray was loaded with 6 cwt. The (blue) dray upon springs had now a weight of 14 cwt. placed upon it. With this additional weight, however, it got before the (red) dray which had no springs. From this experiment, the application of wooden springs to carts upon pavements, or upon ordinary roads, appears to have an advantage in the proportion of 74 to 6. It must be observed, that a perfect coincidence of draft could not be obtained; because the carriages to be compared rolled upon different tracts of the pavement, so that the smallest inequality of the roads must have made some difference in the relative progress of the carriages; but to make as fair a comparison as possible between their drafts respectively, that carriage which was placed on the northern track, as the carriages went from east to west, was in its return placed on the Bouthern track. Some small variation of the draft might be occasioned by the elasticity of the long perch, and some by the vibratory motion of the fore carriage, which was drawn by a single rope. But to those conversant with the subject, these slight variations were but of little moment. The result of these experiments fully prove, in the opinion of this Committee, That the apparatus invented by Mr. Edgeworth is adequate to the purpose for which it is intended: That it may be considered as a sure criterion of the relative draft of carriages: That very short perches do not contribute to the ease of drafts: That the dangerous system of loading the tops of carriages is by no means advantageous. Signatures to the Report of the Committee respecting Mr. Edgeworth's experiments:-R. B. Bryan, Charles Cobbs Beresford, Robert Hutton, N. P. Leader, Richard Griffith, jun. John Patten, Richard Wynne, J. Lester Foster, and P. D. La Touche. * THE numerous accidents which have of late years happened in the coal-mines of this district, have been productive of sorrow and wretchedness to many, and have excited commiseration and horror in all. To hear of 50, 60, nay 100, of one's fellow creatures being suddenly shut up within the bowels of the earth, a certain proportion of them instantaneously destroyed, the rest left to perish, either by hunger or slow suffocation, is such a piece of intelligence as shocks and outrages every feeling of the heart; yet it is a calamity which the inhabitants of the district of the Tyne and Wear are doomed very frequently to deplore. The risk and the frequency of these misfortunes are doubtless owing in no small degree to the great depth and extent to which the workings of the coal-mines penetrate, and the difficulty thence arising of avoiding wastes, and of maintaining the air in a state fit for combustion and respiration. To a certain degree, therefore, they are perhaps unavoidable. But what tends greatly to embitter the regret felt on their occurrence, is the alleged prevalence of a certain disinclination in those concerned in the working of coal-mines, either to communicate information on the subject in general, or to promote, with all the zeal that might be expected of them, those measures necessary for the discovery of the means of preventing accidents. Unhappily, the air of secrecy, In the many fatal accidents which have occurred within my knowledge from explosions of inflammable gas, I think I may venture to assert, that not more than one-fourth of the persons they have ultimately killed have been the victims of their immediate effects; three-fourths of them almost invariably perish by suffocation. (Vide First Report of the Sunderland Society, p. 12.) which they seem so desirous of maintaining, affords but too much room for censure, and subjects them to unfavourable imputations, of which they are probably wholly undeserving, and from which a different conduct would assuredly exempt them. Of their repugnance to grant information, both yourself and Mr. Bakewell have had experience, and have seen cause to complain publicly; and it is to be hoped that it will at last give way, if not to a spirit of liberality, or the power of conviction, at least to the force of necessity. Instances of the loss of lives are becoming so frequent, and of such frightful magnitude, that proprietors, occupiers, and workers, of coal, must in the end be driven to the necessity of rousing themselves in their own defence, for the benefit of their suffering workmen, and of their own interest. It would, Sir, require but few arguments to prove that the system of mystery which they are anxious to preserve, so far from enhancing the value of their concerns, must, in every point of view, operate to its depreciation; and that the tendency must, instead of diminishing, be every day increasing. It would also be easy to show that the only mode left of averting the ruinous finale to which the whole is hastening, is to promote, and even to invite, investigation and publicity. But, Sir, it is unnecessary, if I were capable, which I certainly am not, of writing a dissertation on coal-mines. The subject is not new; and in the present state of our information there is scarcely any thing very interesting to be offered on it. The whole that I intend at present is to draw your attention, and, through your means, the attention of the public, to certain points in the economy of coal-mines, which are already known, from which I am inclined to think advantage may be derived, if they should come to be improved with that eagerness and energy which their importance so justly demands. I shall advert to these in the order they occur to my mind, without much adherence to methodical arrangement. Fire-damp, or, in scientific language, the explosion of carbureted hydrogen, as being the most frequent, apparently the most destructive, and (as in the present instance) the most recent, cause of mor tality in our coal-mines, naturally and forcibly claims precedence. It is to the prevention of this occurrence that the principal attention has been directed; yet, notwithstanding all that has been done, the security against its ravages is still very imperfect. The generation of carbureted hydrogen, from whatever cause it originates, is so incessant and so enormous, that with all the perfection to which ventilation has hitherto been carried, it is found altogether impracticable wholly to guard against those tremendous subterranean com bustions, the effects of which produce lamentation, and woe, and misery, to all in their immediate vicinity. Two years ago a society was established in Sunderland for the express purpose of preventing accidents in coal-mines. Its first Report was lately published, containing a letter addressed to Sir Ralph Milbanke, the President, by Mr. John Buddle, who is, I understand, deservedly considered one of the most scientific and experienced coal viewers in this quarter. That letter contained an account of the methods most generally pursued of ventilating coal-mines, accompanied with draughts illus trative of the different descriptions. From these one may form a very accurate notion of the principle upon which the ventilation proceeds, and that it of course depends upon a thorough circulation of atmospheric air being kept up through all the different coursings and workings of the mine. So rapid, however, is the ordinary accumulation, and sometimes so unexpected is the accession of inflammable gas, that with all the apparatus of ventilation in the most complete condition, it is a matter of no small difficulty to keep the air in circulation in a state fit for the various purposes, or in the language of miners, to prevent it from reaching the firing point, or point of hydrogenous impregnation at which it explodes when brought in contact with the flame of a candle. The slightest interruption to the regular transmission of atmospheric air, or the least unlooked-for addition of carbureted hydrogen, exposes the lives of the miners to the most imminent jeopardy, and the mine itself to the risk of total destruction. It would appear that as far as mechanical means are adequate to the end, ventilation has reached the utmost point of perfection of which it is susceptible. Mr. Buddle in some measure stakes his reputation as a viewer on the opinion, that any further advancement in the discovery of mechanical powers for the ventilation of collieries is unattainable. His words are: "On the strength of my own experience in collieries thus circumstanced, I freely hazard my opinion, that any further application of mechanical agency towards preventing explosions in coal-mines would be ineffectual; and therefore conclude that the hopes of this Society ever seeing its most desirable object accomplished must rest upon the event of some method being discovered of producing such a chemical change upon carbureted hydrogen gas as to render it innoxious as fast as it is discharged, or as it approaches the neighbourhood of lights. In this view of the subject, it is to scientific men only that we must look up for assistance in providing a cheap and effectual remedy." (Report, p. 23.) These positions, though perhaps not very accordant to the genuine spirit of philosophy, as tending rather to repress than to animate the zeal of discoverers, may in the present case be assumed as principles for the purpose of simplifying and facilitating the discussion. By the publication, therefore, of Mr. Buddle's letter in the Report alluded to, our knowledge of this part of the subject may, in one respect, be considered as having not only advanced a step, but our perceptions of what we do know, and of what remains to be done, are rendered more clear and precise. According to this view, then, we may be said to have arrived at a fixed point. We have reached, as it were, a spot from which we can see more distinctly the route to be pursued. A person, in every respect qualified to pronounce a deliberate and decided opinion, has declared that all further attempts at improvement in what may be called the mechanism of ventilation will prove abortive, and that it is to scientific men that we are to trust |