MECHANICAL AND USEFUL ARTS. 21 



frequently used for the recovery of this notable loss ; but apparently 

 ,from a misapprehension of the quantity of water necessary to be dis- 

 charged, and a want of knowledge of the amount of service required to 

 absorb the discharged heat, of a capacity greatly too small for their pur- 

 pose. If Peclet's formula for calculating this surface is to be trusted, 

 those chests on board the West India mail steamship La Plata, and 

 some of the British and North American Company's packets, are 

 ^th to -^th of the size that would be efficient. When these brine 

 chests, regenerators, or heat economizers, therefore, are made with a 

 sufficient amount of surface, so that abundance of water can be sup- 

 plied to and discharged from tlie boilers, with little loss of heat, then 

 there will be no incrustation of boilers, and a probable saving of from 

 12 to 13 per cent, of their fuel. Peclet's formula, or Professor 

 Eankine's reduction of it, which gives the probable amount of surface 

 required for a difference of temperature of 110° between the feed and 

 the discharged water, at T Vth. square foot per lb. of brine discharged 

 per hour, becomes under the same circumstances, and when the 

 quantity of brine discharged is equal to the quantity of water eva- 

 porated, iVtb square foot of surface per lb. of water evaporated per 

 hour. The introduction of Dr. Joule's spiral wires to the system 

 will probably render less surface efficient. This amount of discharge 

 and surface, it is expected, will prevent incrustation, and save nine- 

 tenths of the heat at present lost." 



GREAT CHIMNEY AT GLASGOW. 



Mr. Duncan Macfarlane, of Glasgow, C.E. and architect, has 

 published a description of the colossal Chimney recently completed at 

 Messrs. Townsend's Chemical Works, Crawford- street, Port Dundas. 

 It is described as being not only the largest structure of the kind, but 

 the loftiest building in the world, excepting the Great Pyramid of 

 Ghizeh, the spire of Strasburg Cathedral, and that of St. Stephen's, 

 Vienna. This chimney is circular on plan. 



Total height from foundation 46S feet. 



Height above ground 454 „ 



Outside diamet?r at level of ground ... 32 ,, 



Outeide diameter at top 14 ,, 



Thickness at level of ground 7 bricks. 



Thickness at top li „ 



In a report made on its probable stability, Professor Eankine 

 says — ''From previous experiments on the strength of the bricks 

 used in the chimney, I consider that their average resistance to crush- 

 ing is 90 tons per square foot. I calculate that, at the level of the 

 grouud, the pressure on the bricks arising from the weight of the 

 chimney, will be about 9 tons per square foot, or T Vth of the crush- 

 ing pressure. I consider that, in violent storms, the pressure on the 

 bricks at the leeward side of the chimney may sometimes be increased 

 to about 15 tons per square foot, or Jth of the crushing force. On 

 these grounds, I am of opinion that the chimney, if executed as 

 designed, will be safe against injury by crushing of the bricks." On 

 the 9th September, 1859, however, after a hurried construction, a 



