more than ten days. He would recommend in place of it separate confinement, by which contamination might be prevented. [In the preceding abstract of the proceedings of the different Sections, we have no ticed those papers and communications only which are likely to be of interest to our readers.] GENERAL OBSERVATIONS. (From the Athenæum.) The meeting of the Association is over; but before we proceed to draw up a record of its proceedings, we must say a few words on the general results of the week, and the impression left on our minds. On former occasions, hospitality has been shown by the residents of the place of assemblage to the way. faring visitors, and the business has preserved the "even tenor of its way;" but in Dublin, notwithstanding the unusual quantity and quality of the scientific communications, business has been positively perplexed by the joyousness and festivities of the occasion. The Irish are a fine, generous, and hospitable people on the first word of an approaching avatar of science on the shores of the Green Island, they set themselves seriously to work, to contrive how they might best do the honours by the distinguished associates whom they expected, and by themselves and the country they represented. To do them justice, they neither spared money nor trouble to please and accommodate their guests, and to prove that, as far as concerns the respect for science, and the savoir vivre Non tam aversus equos Tyriæ sol jungit ab urbe. (Every body knows the applicability of this local epithet, and the Phoenician cradle of the Hibernian people.) In all these respects they succeeded, usque ad delicias votorum. Every practicable accommodation has been afforded for the lodging, feeding, feasting, and amusing of the strangers; and the visitors are, at this very moment, packing up their carpet bags, in high good humour, and "shut up in measureless content." Déjeuners, dinners, rural excursions, public entertainments by the learned bodies, and private parties by individuals of distinction, have exhausted all their combinations, to scatter the flowers of sociality over the path of scientific labour; and if many go away not much the wiser for their journey, there can be but few who will not depart full of pleasant recollections. In the mean time, a question arises concerning the permanent interests of the Institution and "there's the rub." Setting aside the distraction of mind incidental to the crowding together so much business (for pleasure as well as science has been made a business), the vast numbers of all classes and pretensions who have joined the Association, and flocked to its halls, cannot but have disturbed the march of the proceedings. Imagine the Rotunda,- —a room capable of accommodating from 1500 to 2000 individuals, thronged to excess on some of the hottest evenings of this hot and cometary season: the ladies flirting and fanning; the gentlemen casting one eye upon Science and another upon Beauty; and the whole (saving the reader's presence) moping, and puffing, and ready to drop with exhaustion and fatigue. Then reflect on the sort of attention which those in earnest about the business in hand could give to the discourses of the orators. First, they were fatigued with the labours of the Sections; then trotted about the city to see sights and walk off the repletion of the copious and elegant breakfast which preceded them; then came the hot and crowded ordinaries, with hundreds seated round the smoking viands; and finally hurried off to encounter the jostlings and the stewing of the evening meeting. But the business of the day was not even then concluded, for the rout and the supper had yet to be gone through; and the next morning, with bodies jaded by the labours of the previous day, and minds 'still clouded with the yesterday's feast, the itinerant savans had again to brace themselves for encountering the like routine. Even in the Sections themselves, the scientific were not left in peace; both sexes were eager to attend them; and the ladies, as they could not be in the whole at once, made the best they could of their case, by crowding in shoals to that particular Section where the business was of the most abstract and recondite description. These inconveniences were not perhaps very seriously felt at the moment; amusement and gratitude disarmed criticism; but the truth will, we fear, soon start into evidence, that the Irish meeting has been, all things considered, rather too splendid an affair. Again, will not all this expense, show, and excitement, throw cold water on the meetings of future years? Many will grudge a costly and troublesome journey that is to end in a junketing; and those for whom the pleasure has had its charm, can hardly expect to see the éclat and splendour of the Dublin meeting maintained hereafter. Heaven help the people of Bristol, whose turn comes next! In a city which is nothing but commercial, with no university, no learned and scientific corporations to keep up the ball, not all the turtle in their next fleets can vivify their pro ceedings. On the whole, then, we cannot but fear that the pleasure has been over-done; that the Association has been killed with kindness; and that the institution will feel the ricochet of this hot fit of delight. But so far as Dublin itself is concerned, the success, it must be admitted, as been complete. ON RAILWAYS. BY JOHN HERAPATH, ESQ. NO. IX. Calculation of the Expense and Time of Transit on ascending and descending Planes. My third Number contains rules for computing the time, velocity, &., of transit, with a table, calculated for any rising inclination not exceeding 60 feet per mile. There is little difficulty, indeed, in computing for ascending planes, but for descending it is no easy matter to determine the limits of descent in which the steam can be fully applied, and those in which it must be partly cut off, with the amount of partial application. We must here, I imagine, be guided by considerations of safety. If 30 miles an hour be the ratio on a level, the question is, at what rate can we safely run down a slight descent? Can we venture 40 miles an hour? If we can, probably this would be the outside with our present engines. Hereafter, we may possibly go at a greater rate, but at present it would be hazardous. Now, full steam applied to a fall of 5 feet per mile, would, by our theorems, in No. 3, give a velocity of 40 miles an hour. If, therefore, we take, in order to have round numbers, 6 feet per mile as the maximum descent at which full steam can be applied, which makes the velocity 414 miles hour, we shall be able to devise per a very easy mode of calculating the time and expense of transit for any length of time, whatever be its rate of practicable ascent, if neither of its descents exceeds in which the plus sign holds when the latter extremity is higher than the former, and the minus when it is lower. This theorem, which is much more accurate than the table in No. 3, is perhaps the simplest that can be given within the limits for which it has been investigated. The expense, too, of transporting a ton of goods, which bears a given ratio to the time, other things alike, is had by simply multiplying (5) by the expense per ton per mile. If a halfpenny be the latter cost, then the expense per ton in pence for the whole distance is at These theorems, as we have said before, apply for all practicable rises, combined with such descents only as do not exceed six feet per mile; where the descents are greater, other methods must be had recourse to. In comparing the southern lines in No. 4, I have considered all descents to be run a velocity of 30 miles an hour, and at a cost of a farthing per ton per mile. As a matter of comparison this may do nearly, both lines being subjected to the same rule; but it is evidently only a rough approximation as regards any one line Indeed, taking descents generally between 0 and the fall beyond which gravity would do all the work, that is 22 feet per mile, I know of no correct rule for estimating either the expense or time of transit, nor, perhaps, can any be given. We are left entirely to our own judgment, unassisted by experience, and in a case in which it would be unsafe to apply theory beyond certain limits. The following views, therefore, are presented merely to fill up a blank, until experience shall furnish us with something better. It is generally admitted, that the more level a line is, the greater is the velocity which can be run in safety; and that the steeper the descent, the less must be that velocity. Hence it is on the Liverpool and Manchester Railway, that the Directors impose severe penalties on the men if they allow the trains to descend the two principal inclined planes, whose mean fall is about 58 feet per mile, at a greater velocity than 24 miles an hour; though down the easier planes, and on levels, velocities of 35 miles or more au hour are often attained, and I believe permitted, because they are not considered dangerous. Now, if starting from our fall of six feet a mile, at which the velocity, with full steam on is about 414 miles per hour, or a mile in 1 minute 27 seconds, we gradually diminish the velocity by increasing the time of transit, at the rate of one second a mile for every extra foot of fall in a mile, we shall at 58 feet fall per mile have a speed of one mile in 2 minutes 12 seconds, or 26 miles an hour. This, therefore, gives a scope for improvement on the Liverpool line of about two miles per hour on their two inclined planes. To what greater length this progressive increase of time may be carried is difficult to determine, possibly to a fall of at least double the rate of descent; but as it is to be hoped no railway for passengers will ever again be constructed with such planes, we need not, perhaps, trouble ourselves to inquire into the extent of application. On these principles, the time of transit down planes descending more than six feet per mile, is likewise easily cal eulated. It is only multiplying the length of each descending plane in miles by 1 minute 27 seconds first augmented by as many seconds as the fall per mile exceeds six feet, and the sum of the times will be the time of descending all the planes. In regard to the expense of fuel, it appears to me, if the descent of any one plane does not exceed ten or twelve minutes of time, that is, five or six miles of length, little or nothing can be saved though all the steam be turned off; for, if the fire be not kept up, and the temperature of the water be allowed to sink, the engine will not be prepared for working the subsequent rise or level. Therefore, supposing as before the consumption of fuel to bear a constant ratio to the time, the expense of trans porting a ton of goods is in pence found by taking of the whole time of transit in minutes, or by multiplying the mi nutes of transit by such a decimal of a penny as the cost on a level actually is, whatever be the inclinations, if no one descent exceeds a run of about ten or twelve minutes, or a length of about five or six miles Though the expense of transit for fuel is considerable, it would appear, from the Liverpool and Manchester half yearly Reports, that the expense amounts to not more than a fourth or a fifth of the actual cost for locomotion. The men's wages for repairing, and the materials used for the repairs of the engines, &c., often exceed each the cost of fuel. This certainly argues very much against the present state of our machinery, and of the locomotive power on the Liverpool and Manchester line, and tells us, in no equivocal language, that the field for improvement is hitherto but little cultivated. On the face of it, we should say, if the machinery was in any but a most imperfect state, so great a disproportion could not exist between the aliment of motion and the mere wear and tear. I beg to observe I do not state this complainingly, but as a simple fact, and as a fact to stimulate our aspiring mechanics to bend more intensely their minds on the improvement of this valuable instrument. One of the most important steps towards the perfection of locomotive engines hitherto made, is that of sending the hot air and flame through the numerous small tubes traversing the water in the interior of the boiler. This improvement, I believe, is due to the suggestion of Mr. Booth, of the Liverpool and Manchester Railway. Without some such contrivance for increasing vaporization, the power of the engine would have been still exceedingly feeble. The first tubes were three inches diameter, and they are now, I believe, reduced to under an inch. If they could be still further diminished in diameter, and increased in number, it would contribute much more to the steam-generating power of the engine; while, I apprehend, it would greatly lessen the burning out of these tubes, and, consequently, the excessive expense of repairs. For, as the thickness of the tubes may be diminished in proportion to the diameter, if the diameters were, by way of example, reduced one half, and their thickness in proportion, the temperature of the heated air or flame passing through the tubes would be communicated to the water, and, conversely, the temperature of the water to the interior of the tube, in one half the time, or with double rapidity. Consequently the temperature of the interior surface of the tubes will always be kept nearer that of the water, that is, much lower than with thicker tubes, and the exfoliation of the tubes by the blast, or the burning out of them, therefore diminished; for the nearer the temperature of the tubes can be reduced to that of the water the better. If it was possible to keep them to the same temperature, they would, perhaps, hardly ever burn out. Besides, by diminishing the diameter to a half, we must quadruple the number of tubes, in order to carry off the same draught. This would double the heating and heated surface; and therefore, in my opinion, further diminish the exfoliating power of the fire by spreading its influence over a greater surface. Limits, however, must be set to this reduction of diameter. If the tubes were too small, they would be in danger of being choked by the particles of coke driven into them by the strong draught through the fire. Again, there would be a great inconvenience in the number of them. For instance, if the diameters were reduced one half, and the number of tubes quadrupled, at length, by going on in this way, we should fill the boiler entirely with tubes, or have them so thick as to have nothing but one mass of steam among them, particularly towards the fire-box end, by which most serious accidents might be engendered. However, it is well worth the while of mechanics to try to find the minimum diameters to which the tubes can be efficiently reduced. It is purely an experimental subject, and I have no doubt would well reward the labour of inquiry. It once occurred to me, that if the tubes were conical instead of cylindrical, it might be advantageous; but on more mature consideration I do not think it possibly could. Supposing they were conical, and that the less ends were towards the fire-box, their thicknesses gradually increasing with their diameters; then, though we should gain all that we have previously described with respect to reducing the diameter and thickness of the tubes, yet if the velocity of the hot air through the tubes bore any sensible ratio to the velocity with which such air transmits heat, that is, to the velocity with which the said air so heated would conduct sound, there would be a very serious loss of temperature by the expansion of the air, owing to the enlargement of the tubes as it passed through them. And, if the large ends of the cylinders were next the fire-box, though it may be the best possible arrangement-and we should certainly gain much where we before lost-yet, in practice, it may be attended with great inconvenience, from the disposition of the tubes to choke. The chief defect in the present locomotive boilers, is, in my opinion, the having of the fires at one end, and the want of a more equal distribution of heat through the water. A boiler, a description of which I have lately seen, invented by Mr. Joseph Gibbs, one of our civil engineers, appears to me to be grounded on good philosophical principles; but how it would answer in practice I am unable to say, never having seen it in work. His principle is to have the fire-box not far beneath the surface of the water, and to send the heated air in a spiral tube downwards towards the bottom, about which the jet of cold water is introduced. But enough of this subject; I have now not time to go into it. I am glad to find that since the publication of my observations on the excessive expense of carrying private Bills through Parliament, the subject has been taken up in the House; and I have again since heard it is intended to be brought forward next Session, and supported by several influential Members. I shall recur to it shortly. But it is not on the subject of Parliamentary expense only the public feeling wants to be roused; there are others of deep importance, which need to be brought before them. I hope I shall not presently be goaded to lay bare a scene of injustice, jobbing, and base trickery, that will make knaves themselves stare, and honest men shudder. JOHN HERAPATH. Kensington, August, 1835. Dear Sir, I enclose some papers relative to Halley's Comet, which I originally intended to keep for my own private use, but considering that they may be of more extensive utility were they to find a place in your valuable Magazine, I send thei to you for publication.* The path of the comet is taken, with a few corrections, from the Nautical Almanac. Pall Mall, London, August 22, 1835. E. HENDERSon. Table of the Right Ascension, Declination. Meridian (London) Allitude, and Meridional Passage of Halley's Comet of 75 years. One of the papers thus obligingly sent to us is a very accurate projection of the orbit of the comet and the part of the heavens through which it passes. We thought we should have been able to get this engraved in time for our present number; but as we find this to be impracticable, and the information contained in the other papers would suffer from delay, we must refer the reader, who may require the aid of a chart in his observations, to that given in the Nautical Almanac, or to the copy of it in the Companion to the Almanac for 1835. |