constantly in a state of motion, so that the surface of the excreta will be constantly exposed to the hot air, thereby thoroughly drying it. The drying is effected by connection of a large pipe to a boiler specially constructed for burning the cinders and vegetable refuse referred to, the heat as hot air passing through the pipe and through the revolving cylinder or machine, and absorbing the water of the excreta, the effect of which is that a charge of 3 tons 10 cwt. of excreta is reduced in about eight hours to 5 cwt. of material, very similar in appearance to hard dry clay. To each ton of the excreta there is added 20 lb. sulphuric acid, and thus the ammonia is fixed and not driven off by the heat. The heat passes from the machines through flues, is utilised for completing the drying on a drying floor, and conveyed to condensers, which reduce the temperature and drive off the vapoury particles; it is then forced by a blower through a furnace, and finds its way up the chimney. The manufactured product is taken from the machines, placed in an adjoining shed, and ground in a pugmill to a "poudrette.” The following analysis by the borough analysist, shows the composition of the manure : * Containing nitrogen equal to 6·71 per cent. of ammonia, or cal- + Equal to 1.84 per cent. of soluble phosphate of lime. N.B.-Before being sent away the manure is further dried by being spread out on the drying floor as above explained, until the moisture is reduced to about 12 per cent. As the works are at present in a transitory state, it is almost impossible to say what will be the amount of manure, and the cost of manufacture, but the demand for concentrated manure so far has exceeded the supply. It is hoped at an early period to give an account of the result of the working of these late improvements. The Members also viewed one of Lyon's patent disinfecting machines which has lately been erected at these works. Votes of thanks were passed to the Mayor for the use of his reception room, and to Mr. Alderman Taylor, and Mr. T. B. Ball (gas manager), for their kindness and attention to the Members on visiting the manure works and gas works. WILKINSON'S TRAMWAY LOCOMOTIVE. Extracted from a Paper read before the Liverpool Engineering Society, 25th April, 1883. OWING to the ever-varying conditions under which the boiler of a tramway locomotive has to work, due to the sudden changes in the nature of the roads, from dead levels to the steepest inclines (as, for instance, at Huddersfield, from level to 1 in 11), which does not happen in railway practice (a gradient of 1 in 75 being considered excessive on a railway), the boiler of a tramway engine should be of the most sensitive nature, as one moment it necessarily is not required to generate steam, save in a very small quantity, and in the next it is called upon to work to its utmost evaporative power as above, which sudden requisition obtains more or less on all steam-worked tramways, owing to the before-named sudden changes in levels. The boiler is an improved Field's patent, viz. vertical, with an internal fire-box, which gives an annular water space all round, between the outside of fire-box plates and the inside of boiler shell plates, as is usual in all vertical and locomotive boilers. The crown plate of fire-box is perforated with a number of holes, and into each hole is fitted a hanging tube, which tubes are closed at the lower end, and when at work are consequently full of water. These tubes hanging from the crown of fire-box are exposed to the most intense heat of the furnace, which is placed immediately beneath them, and being th of an inch thick only in section of metal (iron), must necessarily be extremely sensitive generators of steam, and would boil dry intermittently if they were not provided with some appliance to counteract that evil, which is done as follows: Each tube has, hanging loosely inside it, another tube fitted with conical mouthpiece, with three feathers or wings on the underside of cone to preserve an annular space between the top end of the large tube and the underside of cone. The action due to the natural law (the difference in specific gravity between hot and cold water) that the cooler water always descends to the bottom, is as follows, viz.: As soon as heat is applied to the external surface of the tube which hangs over the fire, the water in the annular space between the inner and outer tube begins to ascend, and is somewhat deflected by the cone at the top, and the cooler water begins to descend the inner tube, and as the heat is increasing so in a proportionate rate is the speed of the two currents (ascending and descending) increased, thereby creating a very rapid "circulation" and bringing every particle of water rapidly in its turn into close contact with the fire or furnace, with an interposition of only 4th of an inch of iron between the water and said fire. These tubes being fastened only at one end in the tube plate, the other end hanging free over the fire, are at liberty to expand or contract to any extent, and thereby are not in the least affected by unequal and varying temperatures as in the locomotive type of boiler, where the tubes are secured at each end in a rigid tube plate, and are a constant source of annoyance in small locomotive boilers, by the fire-box tube plate becoming leaky after a few months' service, these leakages never, under any circumstances, happening in this boiler. Whenever the boiler should happen to get short of water through carelessness and inattention, the crown plate of fire-box is the first part to become exposed, and consequently the tubes will boil dry at once, and being so much thinner in section of metal than the tube plate, coupled with the fact that they are so much nearer the fire, the consequence is, that one or more of them will simply tear open at the lower end and allow the steam and a little of the water to escape harmlessly and put out the fire at once before the crown plate can become overheated and do any damage. This type of boiler can be examined in every part by the eye, and can be got at easily by the hand in every part for cleaning thoroughly, which cannot be done in the locomotive kind, where trust has to be put to "Providence and a hose pipe" for cleaning. Inside the boiler at E E, Fig. 1, is fixed a loose dish to catch any hard mud or scale which may from time to time drop from the uptake at the water level where such mud often accumulates, and dropping off into the conical mouth of internal tubes, impedes the free circulation of the water, and causes damage to the outer tube by burning. Further, this boiler has been well tried and tested under the most extreme pressure of hard firing for sufficient length of time to establish its lasting qualities: i. e. the Leeds and Liverpool Canal Company have fourteen of these boilers fitted on steamboats carrying goods between Liverpool and Leeds (128 miles by canal); each boat runs twenty-four hours per day, the boilers being fired to the utmost capacity of their evaporative power, with a much stronger blast and forced draught than is ever required for tramway purposes, and are entirely in the hands of the most inexperienced men, viz. the ordinary canal boatmen (no engine-men being carried, each boatman attending to the engines in his turn whilst the others sleep), consequently the boilers are doing two ordinary weeks' work in one, with a most excellent result, some of |
