132 



NATURE 



[Dec. lo, 1885 



bottom of the upper, iidmits the air in an upward direction 

 to the ceihng abo'* the heads of the occupants. Holes 

 bored in a perr<?ndicular direction in the bottom of the 

 upper sash, Jouvered panes to replace one of the squares 

 of glass, an arrangement for allowing one of the squares of 

 glass to fall inwards upon its lower border and providing 

 it witli side cheeks, or a double pane of glass in one 

 square open at the bottom outside and at the top inside — 

 all effect the same purpose and are simple and inexpensive 

 contrivances. Wall inlet ventilators, as the Sherringham 

 valve and Tobin's tubes, are constructed on the same 

 principles, fresh air, which in towns may be filtered 

 through muslin or cotton wool, or made to impinge upon 

 a tray containing water so as to deposit its sooty particles, 

 being admitted at a height of about 6 feet from the floor 

 and directed upwards towards the ceiling. The usual 

 outlet for vitiated air is the chimney-flue, and this for an 

 ordinary medium-sized sitting-room, with a fire burning, 

 is sufficient for three or four people, provided no gas is 

 alight, or the gas lamp has its own special ventilating 

 arrangements. With an ordinary fire, from 10,000 to 

 15,000 cubic feet of air are drawn up the chimney in an 

 hour. Valves placed so as to open into the flue near the 

 ceiling are sometimes used as outlets for foul air, such are 

 Neil Arnott's and Boyle's valves, which permit air to pass 

 into the flue, but prevent its return ; the only objections 

 to their use are that they occasionally permit the reflux of 

 smoke into the room, and their movements backwards 

 and forwards cause a slight clicking noise. In all new 

 buildings where efficient ventilation is desired, it would be 

 preferable to construct a shaft at one side of, or surround- 

 ing the chimney-flue, with an inlet near the ceiling of the 

 room and the outlet at the level of the chimney top, so 

 that the air escaping from the room would have its tem- 

 perature kept up by contact with the chimney, thus 

 aiding the updraught, w^hilst the risk of reflux of smoke 

 would be avoided. In all new domestic buildings a very 

 great improvement might be effected by providing for the 

 warming of the air before its entry into the apartments. 

 The window and wall inlet ventilators just described are 

 occasionally productive of draughts in cold weather, so 

 that it is more usual to find them closed or stopped up 

 than in action, or else admitting a very insufficient supply 

 of air ; but if the air be warmed before admittance to an 

 agreeable temperature a very large amount may be allowed 

 to enterwithout the fact being known to the occupants. The 

 ventilating stove invented by Captain Gallon, the Man- 

 chester school grate, and other forms effect this purpose 

 in the following manner : Behind the grate, which is lined 

 with fire-clay, is a chamber into which fresh air is ad- 

 initted by a pipe from the outside. The air, here warmed, 

 is admitted into the room by a pipe opening at about the 

 level of the chimney breast and guarded by a grating 

 which can be opened or closed as found convenient. In 

 the Manchester school grate the warmed air is admitted 

 by vertical pipes, like Tobin's tubes, opening on a level 

 with the chimney-piece. The danger in these grates is 

 that cracks may be formed by the heat of the fire in the 

 joints or in the cast-iron plates which surround the air 

 chamber, and thus direct communication be established 

 between the grate and air chamber with the result of 

 deleterious products of combustion being admitted into 

 the air of the room. When the stove is lined with fire-clay 

 there is no danger of the air in the chamber being over- 

 heated, producing charring of the organic matter in the 

 air and an offensive smell, which is so often noticed around 

 stoves where this precaution has not been taken. In 

 Mr. Saxon Snell's ventilating thermhydric stove the fresh 

 air is warmed by passing over hot water pipes in the 

 stove before entrance into the room, the hot water being 

 derived from a small boiler at the back of the grate. 

 The temperature of the water is not high enough to over- 

 heat the air. 



Gas is being gradually introduced for heating purposes, 



and with a reduction in its price we may look forward 

 to its more extended use. There are several ventilating 

 gas stoves by which air is admitted into a room warmed 

 after passing through the stove. It is important to 

 regulate the heat carefully so as not to overheat the stove 

 and the air which is passing through. In churches and 

 other public buildings air is usually warmed before entry 

 by passing over hot water pipes which circulate around the 

 building under the floor. In all large buildings the com- 

 bustion of gas may be made a very effective means of 

 getting rid of foul air. It has been found by experi- 

 ment that the combustion of one cubic foot of coal gas 

 causes the discharge of 1000 cubic feet of air. In theatres 

 where gas, although being gradually replaced by the 

 electric light, is still much used, the extraction of foul air 

 from the roof of the building by the sunlight burners pre- 

 sents no difficulty. The difficulty experienced is the 

 introduction of fresh air from below without causing 

 draughts. In private houses the use of an extraction shaft 

 over the gas chandelier or a Benham's ventilating globe 

 light, or a Mackinnel's ventilator greatly aid the extraction 

 of foul air from the ceiling, whilst the two latter are also 

 useful in providing inlets for fresh air which enters slightly 

 warmed near the ceiling, and is then directed horizontally 

 by flanges so as to be distributed over the room. Outlets 

 in the ceiling of a room may become inlets when a strong 

 fire is burning, as the draught up the chimney will over- 

 balance the extractive power of the gas and cause all 

 other openings into the room to be inlets. We may here 

 mention an ingenious method for warming the air admitted 

 by Tobin's tubes into a room : a row of small Bunsen 

 burners encircles the tube at its foot, and the products of 

 combustion are conveyed away by a tube which surrounds 

 the Tobin and opens into the outer air. 



In large public buildings, where expense is no object, 

 a combined method of ventilation by propulsion and ex- 

 traction presents many advantages. The amount of air 

 admitted can be easily regulated, warmed, cooled, or 

 moistened, and freed from impurities by filtration, and 

 enormous volumes are capable of being so supplied by 

 propulsion and removed by the extractive powers of a 

 furnace. In the Houses of Parliament where this system 

 is in operation, air is propelled by rotatory fans along con- 

 duits to the basement, where it is warmed in winter by 

 passing over steam pipes, and then passes upwards 

 through shafts into the space beneath the grated floor of 

 the flouse. The heat can be regulated by covering the 

 steam pipes with woollen cloths, and in summer the enter- 

 ing air can be sprayed with water or cooled. by passing 

 over ice in the conduits. The vitiated air in the House 

 passes through a perforated glass ceiling in the roof, and 

 is then conducted by a shaft to the basement of the 

 Clock Tower, where it passes into the flue of a large 

 furnace. 



The introduction of electricity for lighting and of gas 

 for heating purposes will, in the case of both public and 

 private buildings, considerably modify the methods of 

 ventilation now most generally used. 



CYCLES 



THE Institute of Mechanical Engineers held a general 

 meeting in the Corn Exchange, Coventry, on the 

 afternoon of Wednesday, October 3S, Mr. Jeremiah Head, 

 President, in the chair, when the Secretary read a paper 

 by Mr. R. E. Phillips, of London, " On the Construction 

 of Modern Cycles," of which an abstract follows : — 



The cycle industry in this country has grown with such 

 rapidity and has already assumed proportions of such 

 magnitude as to lead the author to hope that the present 

 paper may prove of some interest to the Institution. It 

 would not be possible within any reasonable limits to do 

 justice to all matters connected with cycles ; p,nA he 

 therefore purposes dealing only with their general con- 



