HOWELL'S READING EASEL. [Registered under the Act for the Protection of Articles of Utility.] A SINGLE glance at the prefixed engravings will suffice to satisfy any one that this is one of the most valuable presents which has been made for a long time past to the reading public. It is literally an instrument for making reading easy; for reducing it to an affair of the eyes alone, and leaving the hands, feet, in short every other part of the body, at perfect liberty. It forms an occasional appendage to a chair or sofa, which can be attached or detached at pleasure, with almost the same facility as a book can be taken up or thrown aside; and it supports the book while in use at whatever height and distance may suit best the optical powers of the reader. The figures 1, 2, and 3 represent the easel as in actual use; fig. 4, the appearance it assumes when folded up to be laid (like the book) aside; fig. 5 is a side elevation, and fig. 6 a front elevation of the instrument by itself, and on a larger scale, than in the other figures. A is a horizontal foundation piece, which is slightly arched on the inside, and from a to b on the top surface cut with ratchet-shaped grooves in it, as indicated by the dotted lines. B is an upright, consisting of two pieces connected together by a hinge at d, and attached at bottom by a strong hinge-joint to the horizontal foundation piece Ă. C is a spur, which is hinged to the back of B, and when let down takes into the ratchet grooves on the top surface of A, so as to fix the upright B at any When required angle of inclination. the instrument is not in use, this spur is thrown back into a recess made for it between c and d. D is a flap for holding the book or manuscript to be read. It consists of four separate pieces, 1, 2, 3, and 4, connected together at the back by a piece of cloth, or other flexible material connected thereto, so as to allow of the pieces being folded up together, when out of use; the outer piece, 4, is inserted edgewise into a stock, 5; and that stock is made fast to the upright B at any elevation desired, by means of the holdfasts E E. F is a spring inserted between two holdfasts, in order to keep the flap more firmly in the position assigned to it. G is a moveable ledge piece for the bottom of the book or manuscript to rest on; it turns on a pin, e, at one end, and when let down is kept fast in its place (as represented in fig. 2) by a catch, f. A Fig. 5. Fig. 6. E G is a screw clamp attached to the boss in the bottom of the foundation piece A, by means of which the instrument is secured to the side rail of the chair, or sofa, or other seat, of the person intending to make use of it. The clamp embraces the rail within the space H, and is screwed up tightly to it by the screw I. MR. MALLET'S METHOD OP OBTAINING VACUUM FOR ATMOSPHERIC RAILWAYS BY DIRECT CONDENSATION OF STEAM (CONCLUDED FROM P. 214.) WE are now enabled to determine the amount of vacuum that we shall obtain in the six miles of 15-inch tube by the use of the apparatus. The capacity of the tube=38872 cubic feet. r=38872 cubic feet. b-38872 2 =19436 cubic feet. Or assuming r=200, and b=95 as before, we have for the first stroke, 200 d=9687 x 30=20.34 inches of 95 + 200 the rarefaction; and hence the vacuum at the first stroke, MR. MALLET'S ATMOSPHERIC RAILWAY IMPROVEMENTS. To which we have further to apply a correction for the leakage taking place by the long valve, &c., during the time of exhaustion. Supposing both vacuum vessels empty, and the steam surcharged in the boilers, and in a condition to blow off, which would be the state of the apparatus after the passage of one train, and at the moment when a vacuum was required for the second, in such a state of things three strokes can be completed in the time that the air will rush from the tube into the vacuum vessels, added to the time required to fill one vessel with steam, condense it, and again equilibrate its amount of vacuum with the air of the tube. We need not go beyond the third stroke, because it is plain that at it we shall have a vacuum sufficient to start the train. It is therefore necessary to determine the time of blowing off the steam into the vacuum vessels; of the air from the tube rushing into them, and of the condensation of the vacuum vessels full of steam, which latter is only limited by the time in which the steam from the vacuum vessels can get into the condenser. These times cannot be correctly calculated for want of experimental data. The usual formula give no approach to the results shown by experience. Judging, however, from experience in analogous cases, I estimate that 227 The steam at 45 lbs. will fill the vacuum vessel in from thirty to forty seconds, expelling the air before it; the dimensions of the tubes being such as shown on the drawings. The air of the tube will equilibrate with the vacuum vessel in from twenty to forty seconds. The time of condensation will be ten seconds. Now, Barlow states that the vacuumgauge fell at Wormholt Scrubbs at about the average rate of 4 inches per minute, when all was at rest, by leakage, the vacuum being from 21 to 12 inches of mercury. Now in vessels of unlike capacity, but with the same amounts of leakage and vacuum, the fall of the gauge in the same time will be inversely as the capacities of the vessels leaked into; and as in the present case the railway tube will be constantly in communication with one vacuum vessel of half its own capacity, the average fall of the gauge per minute by leakage, on half a mile of 15-inch pipe, will be reduced in the proportion of the capacity of the 15-inch tube + the vacuum vessel, to the capacity of a 9-inch tube. We may, therefore, in round numbers, consider the leakage as equal to an average fall of the gauge of 1 inch of mercury per minute. The vessels, as stated, being already exhausted, the times of the first and second strokes will be forty seconds each, and the time of the third stroke will be about eighty seconds. We have therefore at the first, second, and third strokes the following falls of the gauge due to leakage :— four strokes made at equal intervals during the transit of the train will more than meet this; or as the transit is made in twelve minutes, we must have one stroke made every three minutes, and for this the boilers are adequate. We have thus then to complete the transit of one train over six miles of 15inch pipe to make seven strokes. But we have already shown that each of these requires 12 cubic feet of water to be evaporated from 70° Fahrenheit into steam at 45 lbs. per square inch, and that each cubic foot so evaporated consumes 5.9 lbs. of coal. Hence, to pass one train over six miles, we must consume 5.9 × 12=70'8 x 7=495'6 lbs. of coal; or say 500 lbs. of coal, including the power to feed the boiler and open valves. We have further to determine the amount of power requisite for feeding the boilers with water, and for opening the valves, &c. Four cubic feet of water is to be evaporated per minute at 45 lbs. per square inch-3 atmospheres, which is equal to four cubic feet of water raised 3 x 34 feet =102 feet + the lift of the suction pipe, say 10 feet more=112 feet in all. This is 4 x 62.5 × 112 feet=250 lbs. 112 feet per minute, or 28,000 lbs. 1 foot high per minute, or less than one horse power. The opening of the valves would probably, from their construction (double beat), not require one-half of this-but assume it as much, then two horse power will be more than enough=20 lbs. of coal per hour, or about 3 lbs. of coals per train passed over six miles. Let us now compare this with the consumption of coal requisite to pass one train over six miles of 15-inch pipe by the present air-pump system. At thirty miles per hour the six miles is passed over in twelve minutes. The air-pump must make as many strokes as will clear the pipe of air during this time. At Wormholt Scrubbs, capacity of pump 14.4 cubic feet, and the ratio of the pump to the pipe 1: 85. Capacity of six miles of 15-inch pipe-5280 × 6 × 1.23=38966 cubic feet. Ratio of tube to pump 38966: 144, or as 2710: 1. Hence the pump must make 2710 strokes in twelve minutes 226 strokes per minute. = 2710 =say The pressure for 18 inches vacuum is 5.49 lbs. per square inch; 3.75 feet length of stroke × 226-846.5 feet per minute; area of pump=1104 square inch. 1104 x 5'49 × 846.5 Hence, =155.5 33.000 horse power to discharge the pipe. Assuming the piston and valve leakage the same nearly as for 9-inch pipe, and doubling both for the double length, (which will about compensate for errors in additional joint leakage,) we have the total power for six miles of 15-inch pipe as follows, viz. :— Increasing now the pump space in the ratio of 25: 217, and the vacuum space as half a mile of 9-inch pipe to six miles of 15-inch pipe, or as 1166: 38966, or as 1 24-8, we have The capacity of pump. Cubic feet. 125 The capacity of vacuum space. 38966 or in the ratio of 312: 1. The ratio of rarefaction is therefore 1, and the number of strokes without leakage N_log. 30—log.(30—18) __ 1·477—1·079 _0·398 =199 strokes, log. 312-log. 311 2.494-2-492 ⚫002 to which adding 50 per cent. for lost power, makes 298, say 298, total number of strokes to obtain the vacuum. Then as 58 298 :: 1′ 30′′: the time=463" 7′ 7′′. Hence we have 217 horse power at work about eight minutes from starting to obtain the vacuum, and for twelve minutes to maintain the vacuum during the train's transit-in all twenty minutes, or one-third of an hour; and hence the amount of coal consumed to pass one train, at 12 lbs. per hour per horse power, or at 10 lbs. per hour per horse power, = the former measure is that which may be in practice calculated on, reducing therefore the above in the ratio of 52,000: 33,000 for nominal horse power, we have the nominal horse power 138, and the consumption of coal, at 12 lbs. per hour per horse power, required to pass one train=552 lbs. ATMOSPHERIC RAILWAYS BY DIRECT CONDENSATION OF STEAM. It is, therefore, established that an economy of fuel or of power results by my method over the present system, in the ratio of 500: 552, taking the least favourable views respecting my method, and assuming a perfection in the airpump which does not exist. The largest losses sustained in this method of exhaustion are those due to leakage by the long valve. And if Mr. Bergin's results as to its amount are correct, reducing it in the ratio of 3: 8, the saving in power or fuel by this method would be greatly more considerable than I have here estimated it. It has been shown that the rapidity of producing the exhaustion in the tube, or of obtaining the vacuum, is dependent with a given proportion between the capacity of the vacuum vessels, and that of the tube, solely upon the velocity with which air can rush into a vacuum through a long orifice. i am warranted, therefore, in concluding that the practical limit set by construction and outlay to the size of the vacuum vessels, is within a very large range indeed-the only limit set to the length of tube or distance between station and station. Six miles, therefore, seems by no means to be the utmost limit of this distance. In comparing the rapidity of obtaining the vacuum in six miles of pipe by this method with that of the air-pump and 217 horse power, it will be observed that eighteen inches and upwards of vacuum is produced by this method in two minutes, whereas eighteen inches exactly is only obtained by the engine in seven minutes seven seconds. It seems, therefore, by no means vain to suppose that even three times this length, or eighteen miles of pipe in one length, might be exhausted by this method. The time of exit of the air at that length would not probably equal the time of exhausting six miles by the pump. By combining this mode of producing the vacuum with my other proposal for storing or husbanding it, and also by the very nature of this apparatus itself, which, after the passage of a train, always will permit the steam of the boilers to be worked down in procuring and storing a vacuum equal to the capacity of both vacuum vessels, plus the condenser ; and further, by the application of my proposed arrangements for withdrawing and 229 smothering the fires of the boilers between the trains, I consider that nearly the whole power of the steam would be made available. It is sufficiently obvious that this form of apparatus is at least as simple, and as little subject to derangement, as an engine and air-pump with boilers of equal power; I have, therefore, lastly to show how they stand comparatively as to outlay. ESTIMATE. Apparatus for Direct Exhaustion. 220 tons of boiler work Jacketing. Engine and valve gear, &c. Total £5,575 600 500 1,000 7,675 Apparatus on Existing Plan. 217 horse-power engine and airpump, at Samuda's estimate of 50l. per h. p. for both. . 10,850 Saving on each station, or every six miles in favour of direct exhaustion. £3,175 Without charging the existing system with any outlay for engine station buildings, the whole of which are included in the preceding estimate. Description of the Engravings. Fig. 1 (see No. 1154) is a sectional ground plan of the station buildings, &c. Fig. 2 is a longitudinal section through A B of the station buildings, with side elevation of boilers, condenser, steamengine, and valves, &c. Fig. 5. Transverse section through CD, with end elevations of the vacuum vessels, condenser, &c. a a, &c., are the six Cornish boilers; five are worked together. bb, &c., the steam chests, on top of which are safety valves, as also duplicate safety valves at c c. dd, the air tunnels, conveying draught to the fire-places, as shown in fig. 6, (No. 1155.) e, the smoke tunnel, common to all the boilers, and conveying the smoke, &c., to the stalk f, beneath the boilers. This tunnel is so arranged that any one boiler can be worked irrespective of the others. 9 g, the wheel work, or other gearing, |