Mr. Ure on Ventilation. 273 



walls of tbe case clipped, thus rendering the case air-tight at its lower 

 part. In the centre of the roof there was a tube nine inches high (k) by 

 three and a-half in diameter. At the sides of the i-oof, and at its ends, 

 were a series of additional tubular openings, each three-fourths of an inch 

 in diameter — in all, eleven in number (b). These projected above the top 

 one-half inch, so as to admit of an air-tight cap being put on each. Two 

 other tubes (c), equal in height to the centre one, were placed at either 

 end. These were one inch in diameter, and their use is noticed in the 

 sequel. The bottom of the case was perforated by a number of tubes (d) ; 

 these rising to the height of three inches in the interior of the case. They 

 could be opened or closed as desired. These openings when patent 

 permitted of the ventilation of the case on the most natural, and 

 consequently the most efficient principle. Practical difficulties, how- 

 ever, are in the way of the universal adoption of this system. The 

 apparatus designed by Mr. Ure had in view ventilation by the roof 

 alone, or in conjunction with the upper margins of walls. 



The subjects of experiment and points of comparison lay between 

 the two sorts of tubes first mentioned — the large central aperture 

 and the series of small ones. The case was lifted out of the water 

 channel, and six lamps placed on the case bottom — two at and equally 

 apart from the sides and near to each end, and two in the centre of 

 length. At this period the lamps were burning full blaze. The case 

 was now restored to its place with a diaphragm or division (e), of the 

 exact width, and extending the whole length of the centre tube, thus 

 dividing the tube into two semi-circular vents. By this arrangement, 

 as has long been known, two opposite currents were caused in the tube 

 — one on each side of the diaphragm ; the cold air passing in by the 

 one opening, while the heated air and products of combustion made 

 their escape by the other. In less than three minutes a great decay 

 of the energy of combustion in the lamps was quite perceptible, and in 

 about four minutes all the end lamps were much reduced in flame, and 

 two of them were nearly extinguished. The two in the centre, being 

 those immediately under tlie ventilating arrangement, continued to burn 

 more freely, but still languidly. At this stage the combustion was a 

 I rue maximum, and remained stationary. Its energy was indicated by 

 the whole amount and local distribution of ventilation which the apparatus 

 as used was capable of supplying. The mode of ventilation here ex- 

 perimented on has been lately patented, and is characterised by and 

 distinguished from that of Mr. Ure by one or more tubes placed in the 

 roof, and each equally divided by a diaphragm, the requisite supply of 

 cold, and the emission of heated and contaminated air, being expected 

 to take place by these semi-tubes. 



When the stationary point of ventilation by the model apparatus in 

 use had been reached, the eleven small openings distributed over the 

 top were quickly uncapped, the diaphragtn withdrawn, and an amount 

 of the opening of the largo centre tube, as nearly equal in area as 



