MR. SAMUEL HALL'S REEFing paddles. for there is a great difference between the effect of the atoms in solution in the wetting water, and any deposit on the glass, of these atoms in accumulation. In the plate, the Focal Radiance, surrounded by illumination through the whole glass, is supposed to fall on a plank of a leaking vessel, which it is necessary to examine. Omitting very many other things, I limit myself to the two following observations on scientific theory. It is evident that the heterogeneous light might, by the application of a prism, be separated into its component parts, and that prismatic colours might be exhibited on the paper in the water; and also secondly, that a case is evidently possible, in which the foci might be of real flame. I am familiarized with descending into the watery deep in summer's noontide and wintry night; but my most interesting meditation, or dreamy vision, or reverie, on these subjects, was one day when I descended in the diving-helmet and water-tight dress, sometimes viewing the rocks and sea-plants at the bottom, and sometimes gazing upwards through the crystalline Atlantic ocean, near the wild and caverned, stupendous billow torn cliffs of my native Clare, while the summer sun was gleaming down upon me in meridian effulgence through the water. It was the very sanctuary of meditation. There is a deeply solemn, mystic interest, in scientific meditation on subjects like these of which I am treating, when the soul holds its communion with itself, beneath the waters of the ocean-the mirror of God! Thou glorious mirror where the Almighty's form Glasses itself in tempests; in all time, Calm or convulsed in breeze, or gale, or storm, Icing the pole, or in the torrid clime Dark heaving; boundless, endless, and sublime The image of eternity-the throne Of the Invisible; even from out thy slime The monsters of the deep are made; each zone Obeys thee; thou goest forth, dread, fathomless, alone. I have the honour to be, My dear Sir, your most sincere friend, THOMAS STEELE, Inventor of the Communicating Diving Bell. MR. SAMUEL HALL'S REEFING PADDLES. 453 Sir,-As I almost daily meet with parties who, from not understanding the scientific principles upon which results of the highest importance are derived from reefing the paddle-wheels of steamvessels, and who, consequently, deny the extent of the advantages which I contend will be obtained by my patent reefing wheels, I feel it a duty that I owe to myself, as well as to the public, to give my opinion, as below, of the relative efficient power of steam-engines, according to the speed at which they are working; such being the question at issue, and upon which some of the extraordinary advantages of my reefing wheels in a great measure depend. I give my opinion without fear of contradiction, as I imagine that there are but few persons who will venture publicly to deny positive facts, however they may indulge in speculative opinions (to use the mildest term) privately. As the iron steam barge, to which my reefing wheels are applying, will, within a week from this time, be in activity on the Thames, my statements will be confirmed or be proved to be incorrect before your Magazine for next week goes to the press, and had the slightest doubt remained upon my mind, I should have had the prudence to delay till then giving the present publicity to an opinion upon a subject which I contend is so simple that any competent mechanic will be surprised that it should become a matter of discussion, and so simple that it would be a disgrace to the merest tyro in mechanics not to understand it. If such be the case, I would ask, what value can attach to the opinion of those persons who cannot comprehend that this mode of extracting from engines the full power for which they were constructed (instead of losing one-half or two-thirds of it, as the case may be) will form, simple as it seems, a new and important era in steam navigation. I am, Sir, Your most obedient servant, SAMUEL HALL. Basford, near Nottingham, March 17, 1840. I, Samuel Hall, consider it to be an indisputable fact that all the strokes performed by a steam-engine are coequal in power, the pressure of the steain on one side of the piston, and the state of the vacuum on the other side being assumed to be always the same. Thus for instance every stroke of an engine of 120 horse power calculated to make 24 strokes per minute is equal to 5 horse, consequently, if from the deep immersion of a vessel containing such -engine, or from other causes, its number of strokes be reduced one-half, or to 12 strokes per minute, it will be performing only 60 horse, or one-half of its power, if the number of strokes be reduced to 8 it will be doing the duty of only 40 horse, or one-third of its power and so in proportion to the reduced number of strokes of the engine, will its power be diminished. SOLUTIONS OF ASTRONOMICAL QUESTIONS. Sir, I have not had an opportunity of seeing any of the numbers of the Magazine for this last month; yesterday I happened to see No. 864, in which I find that "Nautilus" has given another solution of Iver Mc Iver's astronomical question, which seems to afford him much satisfaction; whether the scientific readers of the Mechanics' Magazine will be much edified by his last performance I very much doubt. The equation from which he deduces the polar angle ZPS (see No. 858) is tan. a tan. L. cot. L'. cosec. A cot. A, where L and L' are the latitudes of the two places, and A their difference of longitude. Now this equation (in its present state) is not at all adapted for logarithmic computation, on that account "Nautilus" has been compelled to call to his aid no less than three different sets of tables, viz., log., sines, tangents, &c.; log. of numbers; and - natural sines, tangents, &c. Now this The following solution is shorter, and perhaps better, than my first. Using the same notation as in my first solution, and expressing the difference of longitude (2 A) in time. (L+L') = 107° 26' 2" cosec. 0.020428 .. L'=51° 28′ 39′′ cot. 9.900955 (L—L') = 4 28 4 sin. 8.892605 EXPERIMENTS WITH HALL'S HYDRAULIC BELT. Sir,-Hall's hydraulic belt having lately elicited some degree of interest, and as many of your readers may feel anxious to learn something of its capabilities and how far it may compete with the common mode of raising water by the pump, HALL'S HYDRAULIC BELT. both as regards economy and power, I beg to subjoin the results of two trials I lately witnessed in Portman Market. The particulars of which I carefully noted at the time; as also a general comparison with the supposed work of a pump similarly circumstanced. 1st Trial.-From an average depth of 130 feet, with a 7 inch woollen band, the quantity of water discharged in 113 minutes into the cistern was 85 cubic feet, or 74th cubic feet per minute, equal to about 45 gallons. 2nd Trial. From the same depth and with the same band, the quantity of water discharged into the cistern in six minutes was about 49.44 cubic feet, or 8.24 feet per minute, about 514 gallons per minute. The increase of effect in the second trial must be attributed to the engine being allowed to get into full play before commencing to check its work, and also to the additional pressure of steam in this instance (5 lbs. per square inch), consequently, additional velocity of band -although it will be observed, that the work did not follow precisely in an equal ratio. It has been found that the most effective velocity for the band is about 1,000 feet per minute, and that for every additional inch in the breadth of the band, there are from seven to eight gallons gained per minute. It would perhaps be advisable to determine also the best degree of immersion for the lower drum, which could easily be effected, by observing during one of the trials (since the height of water in the well is variable) the period of the greatest discharge. If we take the 2nd experiment to be the average work of the band under the most favourable circumstances, and compare it with the work of a pump in good condition worked by the same power," accordingly to the formula given by Tredgold, we shall find the effect by the 455 band to be about 73% per. cent of the power, while that of the pump is only 53, giving a superiority to the former of about 20 per cent. Certainly a vast advantage, but not equal to what was represented, viz.: that the effect by the band was 87 per cent. of the power. But it should be borne in mind that this comparison is made for a lift of 130 feet; where the friction and weight of the pump rods necessarily absorb a great proportion of the power of the engine; at lesser depths, the results would be more equalized. Thus, at a 20 feet lift, making use of the same rule, the effect of the same power pumping would be 361⁄2 cubic feet per minute, or 226 gallons, equivalent from the above data to the work of a 31 inch band. The question then is, whether to raise a column of water of this breadth would require an additional velocity of band? Under any circumstance, additional power, even supposing the substitution of several small bands. If so, the efficiency of the machine diminished with the diminished lift, a law directly opposed to that of the action of the pump, and one, if established to any extent strongly militating against the economy of its use at short depths. Moreover, it should be observed, in calculating the power of the engine I have used the formula of Tredgold, where nearly 3rds is allowed for waste and loss, an enormous allowance and much greater than is usually made. But after all, these can be considered nothing else than rough comparisons, it would be next to impossible to approximate with any thing like a satisfactory result, to an equation of the two methods without actual experiment of both, and that under the same conditions of trial. I should in conclusion observe, that the principle by which the water is raised and sustained, is not, as has been erroneously supposed by capillary attraction or any material absorption by the belt, but simply from the action of the air about the band, which, partaking also of its speed, passes in a continuous current through the water, and so long as the momentum of this exceeds the gravity of the fluid raised, so long will the column be sustained. March 14, 1840. INDICUS. HOOPER'S REGISTERED POST-OFFICE LETTER WEIGHTS. The principle of these little machines for weighing letters is that of the good old fashioned steelyards, excepting that the fulcrum or point of balance is changed instead of the position of the weight. In use, the results are the same, and the objects of the change in this case seem to have been a desire to obviate the objections which apply to moveable weights. They are attached to stands and frames of various kinds. Fig. 1 is one variety, the steelyard is Fig. 1 నా Figure 2 is another form of the same description of balance. It has only a very short pillar or fulcrum, and to weigh the letter, this must be placed near the edge of the table as shown in the figure. H. Sir,-Having observed in your last number a description and drawing of an improved ball cock worked by two ball levers and cranks, I venture to submit to you a drawing of my patent ball ccck, which, with a small ball, and no extraneous arrangement, performs without any friction a full service of liquor, and does not begin to close until the reservoir is filled to the nose of the cock. By the quiet action of the eccentric at the end of my ball lever, regurgitation and jar of the pipe is wholly avoided. Sudden action is indeed an enemy, which, under the pressure of high service cannot fail in producing evil both in the line of duct and in the machine itself, and I apprehend that its bad effect would be great in J.+J.'s otherwise ingenious design. In my professional capacity as architect and hydraulic engineer, I have used very many of my ball cocks, and find them valuable from the circumstance that they can neither stick nor fail in shutting. The Great Western Railway reservoir at Paddington, is supplied by one of those of a 3 fall water way, and either with low or very high pressure performs its service with great ease and perfect regularity. They may be made from half inch to three feet service. In a few days I will send you for your inspection a drawing of my locomotive gauge cocks, and should you think either them or this communication likely to interest your readers, I should |