the power when working without feed in an abnormal manner, viz. with both the disks revolving in the same direction and at equal speeds. The experiments and their results may be tabulated as follows: Power required to drive a Carr's 7-feet Disintegrator under different conditions at about 400 revolutions per minute. When converting into flour 20 quarters of wheat per hour.... ... Gross indicatæd horse-power. 145 123 63 19 From this Table it will be seen that when the machine is working abnormally, it only requires 19 horse-power to drive it, this power being employed in overcoming the friction of the journals &c., and in driving the disks while acting on the air, after the manner of an ordinary fan. Directly, however, the machine is put to work in its normal way, so as to deal with the air by repeated reversals, the power mounts up to 63-horse. It will also be seen that to make 15 quarters of wheat into flour requires 60 horse-power more than to work the machine when acting upon air alone, or at the rate of 20 horse-power for each 5 quarters of wheat, a rate that is very fairly corroborated by the increased power of 22 horses, as shown by the Table to be necessary when the feed is increased by 5 quarters, viz. from 15 to 20 quarters per hour. Further experiments were made with the object of ascertaining the power absorbed whilst running the machine empty at varying speeds. As this, however, could only be done by altering the revolutions of the steam-engine itself, there were practical difficulties attending the experiments which rendered any great range impossible, and also somewhat impaired the accuracy of those which could be made. The general result, however, showed that the power, as was expected, varied as the cubes of the speeds. Although it appeared, from the foregoing experiments, that the Carr's machine when running empty takes, in round numbers, 50 per cent. of the power used by it when at work upon 15 quarters of wheat per hour, it must not be supposed that it is an uneconomic machine as compared with mill-stones. On the contrary, both in power consumed and space occupied, the comparison is greatly in its favour. To grind 20 quarters of wheat per hour would require at least 26 pairs of 4 feet 6 millstones at work, and these would demand from 200 to 250 horse-power, and would occupy, including the necessary spare stones for dressing, about fifteen times as much space as the disintegrator. On this point of "dressing," Carr's machine possesses a further great advantage. With ordinary millstones one sixth of the number are always out of work for this purpose; and not only are they thus idle, but the wages of highly skilled stonedressers have to be paid. In the Disintegrator nothing analogous to "dressing" is required. The wearing parts are the studs; and judging from appearances, it would be many years before they require renewal. The machine from the principle of its action possessing this peculiarity, that a worn stud, so long as it is strong enough to beat the particles without sensibly yielding to them, will do its work just as well as when it was new. It would be beyond the scope of this paper to enter into the question of the relative qualities of the products of this machine and of ordinary millstones. It ought, however, to be stated that Mr. Gibson expressed himself to the writer as highly satisfied on this point. On a direct-acting Combined Steam and Hydraulic Crane. On the Rainfall of Scotland. By ALEXANDER BUCHAN, M.A., F.R.S.E. Secretary of the Scottish Meteorological Society. The paper was illustrated by a map of Scotland, showing the average annual rainfall at 290 places, many of the averages being from observations carried on through long series of years. The map brought out the large rainfall in the west as compared with the east-a difference which is strongly marked even in the group of the Orkney Islands. The average rainfall in the west, at stations removed from the influence of hills, is from about 36 to 40 inches; but in the east in similar situations the rainfall is as low as from 24 to 28 inches. In casting the eye towards the watershed of the country running north and south, it is seen that in ascending toward it from the west there occurs a rapid but by no means uniform increase, and in descending from it toward the east a rapid but by no means uniform decrease. The largest rainfalls occur almost wholly among the hills forming that part of the watershed of Scotland which is north of the Forth and Clyde. The places characterized by the heaviest annual rainfall are, so far as observation has yet enabled us to determine, the following:-Glencroe, 128 inches; Ardlui, head of Loch Lomond, 115 inches; Bridge of Orchy, 110 inches; Tyndrum, 104 inches; Glen Quoich, 102 inches; and Portree, 101 inches. At no great distance from several of these places the rainfall is by no means excessive, thus pointing out an enormous difference of climate between places not far apart. Along the watershed of that part of Scotland which lies south of the Forth and Clyde, no such excessive rainfall occurs, the highest being 71 inches at Ettrick Pen Top 2268 feet high. This diminished rainfall in the south, as compared with that at places further north similarly situated, is due to the mountains of Ireland draining the south-west winds of part of their moisture before they arrive at these parts of Great Britain. The distribution of the rainfall is very instructive in many districts, as in the valley of the Forth, from the head of Loch Katrine to North Berwick, where the amount varies from 91 to 24 inches; in Clydesdale, where the quantity is greatest at the head and foot of the valley respectively, being considerably less at intermediate places; and along Loch Linnhe and through the Caledonian Valley, where the variations of the rainfall are very great, and strikingly show the influence of purely physical causes, such as the configuration of the surface, in determining the amounts. In all these districts, as well as elsewhere, many cases might be referred to which conclusively prove that the amount of the rainfall is very far from being determined by mere height. In truth it is to local considerations we must chiefly look for an explanation of the mode in which rain is distributed over any district; and hence in estimating the rainfall, particularly of hilly districts, no dogmatic rule can be laid down. From observations which have been made at fifty places for lengthened periods, it appears that the deficiency of the three driest consecutive years' rainfall from the average, is generally from one fourth to one seventh, but that in some cases it is as great as one third and in others as small as one ninth. Since then the deficiency of the three years of greatest drought has varied from about 33 to 11 per cent.; it is evident, at least in so far as Scotland is concerned, that no dogmatic rule can be given stating a rate of deficiency applicable to all cases. If those districts were shaded off in which the rainfall does not exceed 30 inches annually, the great grain-producing district of Scotland would be indicated; and it is interesting to note that in those districts which produce the best wheat the rainfall is lower than elsewhere, being in many places as low as 24 inches annually. On the Rainfall of the Northern Hemisphere in July, as contrasted with that of January, with Remarks on Atmospheric Circulation. By ALEXANDER BUCHAN, M.A., F.R.S.E. On the Great Heat of August 2nd-4th, 1868. On a new Mill for Disintegrating Wheat. By THOMAS CARR. In all previous mills and pulverizing machines the material operated on intervenes between, and is simultaneously in contact with two working surfaces. In this mill the disintegration is effected while the material is falling freely or being projected through the air unsupported, and no individual particle thereof, at the moment of disintegration, is ever in contact with more than one portion of the mill, viz. the particular beater striking and shattering it in mid air. It is also the only mill in which the projectile impetus in the material acted on contributes to its own disintegration. It consists of a series of beaters, formed of bars with open spaces between them, arranged cylindrically on disk-plates, around and parallel with a central axle. Into these disk-plates one end of each bar is rivetted, so that the bars stand at right angles to the faces of the disks, while their other ends are rivetted into rings, which so tie them that each bar is supported by the aggregate strength of the whole. These cylindrically arranged beaters (forming what may be called cages, from the slight resemblance they have to squirrel-cages) are of different diameters, so that when placed, as they are, concentrically one within the other, sufficient spaces may intervene between to isolate each, and give them the requisite clearance, and thus prevent any scrubbing or grinding-action on the material, which might ensue between them if they were rotating in too close proximity. These sets of beaters, of which for flour fourteen are used, are driven by means of an open and a crossed strap with extreme rapidity in contrary directions to one another, right and left alternately. The wheat flows in at the central orifice, and is thrown out by centrifugal force from the first cage at a tangent to its circle, and at a speed equivalent to that at which the beaters of the said cage are rotating, when, meeting the beaters of the next cage moving in an opposite direction, its direction is reversed, and it is again thrown outwards to meet the beaters of the third cage, also moving in a contrary direction, and so on with the other cages until (and that in less than a second from its first introduction) the fragments, reduced to fine flour, semolina, and bran, are delivered in a radiating shower alike from every part of the periphery into a surrounding casing, all the beaters (of which there are about 1000) being thus simultaneously effective, and the balance of the machine maintained. Thus, though with these different sets of beaters each acts independently, they are so arranged relatively to one another that not only is a repetition of the blows on the same material thereby obtained, as many times repeated as there are different sets of beaters, but the centrifugal force generated by the rotation of each set is caused to throw the material forward to the next set. Thus the first set of beaters throws it off and dashes it with great violence against the second, the second in like manner against the third, and so on in directions the reverse of that in which each successive set of beaters it strikes is moving, by which means the blows are enabled to act with redoubled energy on the separated particles of matter as they are discharged against them, precisely in the same way that stones are hurled from a sling. The machine can hardly be impaired by work further than the necessary wearing of the brasses of the four bearings. The crucible steel beaters, it is estimated, should last for ten years at least, and are then capable of being quickly replaced. The It can pulverize easily 20 qrs. of wheat per hour, and dispense with twenty-five pairs of millstones. The percentage of flour from it is nearly the same as from millstones; but the quality of flour from the new mill is greatly superior, it being shattered into a fine granular state, not felled or killed as the bakers call it. disintegrated flour absorbs more water, forms a raw paste of greater tenacity, and, when baked, a whiter, lighter, and much better keeping bread, with the sweet nutty flavour of the wheat most agreeably preserved. The cost of production of flour by this system is considerably less than by any other. Two of the machines have been successfully worked for many months at Messrs Gibson and Walker's Flour Mills, Bonnington, Edinburgh. On the Corliss Engine. By R. DOUGLAS. On the Gauge of Railways, By R. F. FAIRLIE, C.E. Last year, at the Liverpool Meeting of the Association, the author read a paper "On the Gauge for Railways of the Future," in which he pointed out the capacities of narrow-gauge lines, and showed how unfavourably the railway-system, as at present worked, contrasted with such lines when properly handled. He said that experience had confirmed the views he had then put forth; and he showed, by giving the dimensions of his carriages, both for passengers and for goods, that upon a 3-ft. gauge he is enabled to place stock of ample size and of less weight than can be done on the 3-ft. 6-inch lines. Whatever saving may be effected in first cost may be lost sight of, the great advantage lying in the saving effected in working expenses. Every ton of dead weight saved goes towards securing the prosperity of the line; and if we can obtain the ample platform which the 3-ft. gauge gives, combined with so much saving in weight, there is nothing left to be desired. In concluding, the author referred to one or two prevailing errors which he said existed with reference to the narrow gauge. The Rhysimeter, an Instrument for Measuring the Speed of Flowing Water or of Ships. By A. E. FLETCHER, F.C.S. The principle involved in the construction of this instrument is the same as that of the anemometer described by the author in 1869 (Brit. Assoc. Report, Trans. of Sect. p. 48). A straight tube is placed in the current whose velocity is to be measured, and held in a plane perpendicular to the direction of motion, so that the water flows across the open end of the pipe. This induces a tendency in the water of the pipe to flow out, and so causes a partial vacuum in it. At the same time another tube, whose end has been bent round through an angle of 90°, is held parallel to the straight tube in such a position that the bent end faces the current. In this the lateral induction is neutralized by the pressure of the current. The difference between the pressures exerted in the two tubes by the action of the flowing liquid is made a measure of its velocity. In order to accomplish this the tubes which dip into the stream are continued upwards till their ends are on a level with the eye of the observer. These ends are of glass; they are united at the top so as to form in fact one tube, bent in the shape of an inverted U. At the top of the bend, that is, in the centre of this bridge-piece, is a small exhausting syringe or pump. By means of this a partial vacuum can be formed in both of the long tubes whose ends dip into the running water, and the water be made to rise through them into the glass tubes at the top, which form the indicator of the instrument. The water is made to rise so far as to fill but partially the parallel glass tubes of the indicator, in order that a comparison may be made of the heights of the columns. If the terminal tubes below dip into still water, the heights of the columns will be equal, as they are held up by the same pressure; nor will it signify if one of them is further immersed in the water, for their upper ends are connected with the bridge-piece already mentioned. But if there is motion in the liquid into which the terminal tubes dip, a difference of height will be observed; the amount of this difference can be measured by a conveniently divided scale, and from it the speed of the current known. It is interesting now to observe that the mathematical formula which were educed to show the relation between the speed of the current of air, and the difference between the heights of the columns of ether in the indicator of the anemometer, apply correctly also to show the relation there is between the speed of the current of water, and the difference of the heights of the columns of water in the indicator of the rhysimeter. W w v will be the velocity of the water in feet per second. p-difference between the heights of the columns of water driven up the tubes measured in inches. W=weight in lbs. of cubic foot of water. To test the correctness of this by experiment, a steadily flowing stream was selected. The speed taken by the motion of a body floating on it was found to be 1 foot per second. The difference of the height of the water-columns was 0.375 inch. According to the formula the speed would have been 1003 feet per second. This close agreement between the results of experiment and of calculation proves the correctness of the calculations, not only as regards the rhysimeter, but as regards the anemometer also. When the speed of the water or other flowing liquid is so great as to make the difference between the heights of the columns in the indicator inconveniently long, it is easy to introduce a siphon containing mercury. In this the motion will be less in proportion as its specific gravity is greater than that of water. This is necessary when the rhysimeter is used to measure the speed of ships. The formula then becomes p=v2x0-08736, where v velocity of the ship in knots per hour, and p-height of column of mercury in inches. Below is a Table calculated from it; its correctness has been abundantly proved by experience. Hydraulic-pressure tubes for measuring the speed of ships have been adopted by Pitot, Darcy, Berthon, and Napier, but hitherto they have not been extensively used by sea-going vessels. TABLE showing the Speed of a Ship as indicated by the Rhysimeter. TABLE showing the Speed of Currents of Water as indicated by the Rhysimeter. |