274 Mr. Ure on Ventilation. 



possible to the sum of the areas of the eleven small ones, was instantly 

 closed up by means of a cap with an opening in the centre, two inches 

 in diameter (f). The absolute amount of space for charge and discharge 

 was thus left equal to that in the first experiment with the single divided 

 tube. In about 90 seconds the combustion of the lamps was restored 

 to their original brilliancy. The dispersed short tubes supplied the cold 

 air, the heated air making a strong escape by the opening left in the 

 large tube. The entire area of the large opening being about 9'6 square 

 inches ; the sum of the areas of the eleven small ones about 6'5, and 

 the area of the discharge tube in this experiment about 3-1, the sum of 

 these two last are equal to the area of the first or large tube. This last 

 experiment was further continued by closing in succession several of the 

 small tubes so as to reduce the energy of combustion to the diminished 

 condition attained and rested at in the first experiment with the single 

 divided tube, being the maximum referred to, as determined, in the first 

 experiment shown. The number of tubes ultimately closed amounted to 

 four, leaving only seven open, when a condition sensibly better than the 

 stationary state then referred to, was in three minutes arrived at. At 

 this stage the combustion was not only less languid, but continued more 

 uniformly distributed. According to this result the sum of the areas 

 of the seven tubes for the descending current being about 4'1 square 

 inches, and the area of the descending tube 3"1, together 7 "2, the 

 ventilation by Mr. Ure's method of the dispersed tubes was as efiec- 

 tive as that in the first experiment (96 square inches), with less than 

 three-fourths of roof opening, while from the uniformity of the rate of com- 

 iustion in all the lamjos, the ventilation was more equably distributed. A 

 third experiment was made, in which the seven entrance tubes remained 

 as before, but instead of the two-inch escape tube, two tubes, each one 

 inch in diameter (c), situated at different parts of the roof, were opened. 

 The result was that the combustion was still as perfect as in the first 

 experiment. The areas of the entrance tubes being as before 4'1, and 

 the areas of discharge tubes 1'56, in all 5"66 square inches for charge 

 and discharge, the dissimilarity in necessary roof opening came to be 

 9'6, as compared with 5'66, or little more than one-half The cost for 

 the erecting on the large scale of the two arrangements, when calculated, 

 was found to be in favour of Mr. Ure's proposed method. Other experi- 

 ments bearing on the certainty and direction of the currents, were suc- 

 cessfully exhibited to the meeting. 



Mr. Ure, in conclusion, considered that distinct tubes, of unequal 

 lengths, should be employed in ventilation, the taller for the ascending 

 current, and the shorter for the descending ; that the tubes, particularly 

 the smaller ones, so as not to interfere with the uniform appearance or 

 elegance of buildings, might be distributed around the upper walls, or 

 on the roofs of the apartments. Those for the ascending current might 

 consist of one centrally placed or several judiciously disposed at inter- 

 vals along the roof, or otherwise, according to convenience or necessity. 



