624 GASES, DIFFUSION OF 



months' test in Gottingon, when it was applied to forty street-lamps in tho principal 

 thoroughfares; and tho Gas Commission certified that the apparatus had worked 

 continuously to their satisfaction. But the experiments more recently conducted at 

 Preston were as follow : 



' The apparatus was fitted to a lamp near the Lady's Walk, Moor Park, a mile and a 

 quarter distant from the gas works in Glover Street, whence the apparatus was to bo 

 operated. Tho times having been previously agreed upon at which tho lamp should 

 be lighted and the light extinguished, watches were carefully compared, so that the 

 feasibility of at will almost instantaneously changing the gas-prossuro in tho lamp 

 apparatus to a definite extent, by means of a regulator at works far removed from the 

 lamps, might be demonstrated. The regulator in Glover Street being operated upon 

 at the agreed times, the lamp a mile and a quarter distant was lighted with scarcely 

 any perceptible lapse of time, left burning for five minutes, as had been previously 

 arranged, and then was promptly extinguished. This process was repeated several 

 times. Similar experiments were tried on a lamp in Ribblesdalo Place, and on 

 another in Fishergate, the two being in sight of each other, about a quarter of a milo 

 apart, and tho same distance from the gas-works. They were lighted simultaneously 

 by one operation on tho regulator at the agreed time, and both lights were extin- 

 guished promptly when the pressure was reduced. The several lamps used for tho 

 trial were taken at hap-hazard, none of the service-pipes having been tested for 

 defects ; nevertheless, the experiments were considered highly satisfactory. 



' For lighting sunlights the foregoing arrangement is modified, only one battery 

 being used for each cluster of lights. The vessel containing the liquid is placed in 

 the middle, and is carried by a hollow centre-piece above it, from which the several 

 arms or branches of the sunlight project radially. The centre-piece is screwed on to 

 the gas-pipe, whose lower end passes down into the vessel containing the liquid, and 

 is enlarged at its lower part, and leads to the centre-piece above. The lower end of 

 the pipe is closed by the liquid when the gas is at its minimum pressure, and opened 

 by increasing the pressure, tho galvanic circuit being completed for igniting tho 

 gas by a temporary augmentation of pressure, as in the street-lamp apparatus. 

 Tho electrodes are situated at each side of one burner only, across which the 

 platinum wire passes, and all the burners being within lighting range of each 

 other, the whole of the gas jets are rapidly ignited. The dip of the pipe into the 

 liquid may be varied, as required, by simply turning the centre-piece. The requisite 

 changes in the gas-pressure are effected by means of a suitable regulator, as well 

 understood. 



'The office desk, or table apparatus, is an ingenious modification, in which the 

 battery resembles those of the street and sunlight arrangements, except that, there 

 being a hydrostatic tap, and the electromotive fluid being brought into contact with 

 the zinc by the pressure of the gas, the zinc is lowered into the acid by a mechanical 

 arrangement, operated by hand-pressure upon a suitable knob, by which, at the 

 same time, an ordinary gas-tap is opened, the platinum is moved over, and ignites 

 the issuing gas. A spring returns the zinc and platinum wire to their original 

 positions, on the removal of the pressure from the knob.' 



GASEOUS. All permanently elastic fluids are usually so called. Oxygen, 

 hydrogen, nitrogen, are gaseous bodies. 



GASES, ABSORPTION OP. All bodies, liquid or solid, absorb gases, tho 

 amount of gases absorbed depending on some mechanical conditions which are l>y no 

 means satisfactorily explained. This is not the place to enter into any examination 

 of this most interesting and important question. Yet, as the consideration of the 

 phenomena involved is continually pressing itself upon the manufacturer, some brief 

 notice appears necessary. 



Gases are absorbed by liquids under two distinct sets of laws, according as tho gas 

 enters into chemical combination with the liquid or not. The amount of gas 

 absorbed by a liquid, on which it exerts no chemical action, depends on tho specific 

 nature of the gas and tho liquid, on temperature, and on pressure. 



Gases are absorbed by solids in virtue of some power residing upon their surfaces. 

 Tho phenomena of 'catalytic' action, of 'capillary' attraction, and of 'exosmose' 

 and ' endosmoso,' appear to be all duo to the force which compels the condensation 

 of gases, and liquids upon tho surfaces of all solids. Under CHAHCOAL, many 

 examples of this are given. Tho whole subject demands an investigation which it 

 has not yet received, See Watts's ' Dictionary of Chemistry ' for a very full desc-rip- 

 tion of all the important experiments which bwir upon tho subjirt. 



GASES, DirruSIOM 1 OF. All gases and all vapours, have a tcndciu-y to 

 diffuse themselves through one another. Tho spontaneous evaporation of wat'-r is 

 an example of vapour-diffusion. The way in which coal-gas mixes itself with the 

 air of an apartment is one of gas-diffusion. The point to bo remembered, however, 



