82 TEAR-BOOK OF FACTS. 



an ample current of air for all the purposes of ventilation. An entrance to the 

 main passage will be provided in Rose-street, similar to the ordinary side 

 entrances, but of such dimensions as will allow of the ready admission of the 

 main pipes for gas and water, which, as all the service pipes will be laid in sunken 

 channels, can be readily carried to any required point on a small truck kept in 

 the subway for the purpose. Provisions have also been made for the hydrants 

 or fire-plugs, and for the service of the street-lamps, but these are matters of 

 detail which would doubtless be subjects for final arrangements with the ditl'erent 

 companies. 



Careful estimates have been prepared, showing the cost of the private vaults to 

 the houses, the paving of the foot and carriage ways, and the cost of the ordi- 

 nary sewer, including digging, side entrances, ventilating shafts, gullies, &C., by 

 which it appears that the extra cost of constructing the subway as now proposed 

 will not exceed 21. Os. lid. per foot run, or about 11. per foot frontage on each 

 house, which, together with the cost of the vaults, sewers, and road, might either 

 be charged at once on those taking up the ground-rents, or be added as an 

 annual charge, in addition to the ground-rent, and which would of course form 

 a part of the annual rental to be sold when the Hoard should think fit to realize 

 the ground-rents. The estimates in all cases are given at so much per foot rim 

 on the frontages, so that the charge on each house may be seen more readily. 



Premiums were offered by the Board for the best designs for a 

 subway, and we may conclude that the plan adopted was the result 

 of careful consideration of all that were submitted. 



(Nearly forty years since, Mr. Williams, of Birchin-lane, published 

 an octavo volume, projecting a system of subways for the. metropolis, 

 and otherwise advocated the measure at considerable cost, but 

 without satisfactory results.) 



BEGENERATTVE HOT- BLAST STOVES. 



Mr. Cowper's Regenerative Hot-blast Stoves will doubtless intro- 

 duce great improvements, chiefly of an economical character, in that 

 very important business — the iron manufacture. It is now pretty 

 generally acknowledged that a much hotter blast than the ordinary 

 one would greatly improve and economize the production of pig- 

 iron in the smelting-furnace : ironmasters have often tried how far 

 they could go in obtaining a higher temperature, and have of course 

 soon arrived at a limit from the destruction which ensued of the 

 cast-iron pipes ; and it is obvious that there must always be a wide 

 difference between the temperature of the air heated inside a cast- 

 iron pipe and the fire outside the pipe heating it, as there will be the 

 difference in temperature between the fire and the pipe, together with 

 the difference in temperature between the pipe and the air passing 

 through it. These differences must be considerable, in order to 

 ensure a tolerably rapid conduction of the heat ; so that in no case 

 can the hot-blast approach at all near to the temperature of the fire, 

 nor indeed would the cast- iron. stand if anything of the sort were 

 attempted; in fact, it is well known that care is necessary in damping 

 the fires of common hot-blast stoves, when the cooling effect of the 

 air inside the pipes is taken away by the blast being Stopped, at 

 tapping time or on any other occasion. The temperature at which 

 the products of combustion pan away from ordinary stoves is from 

 1250" to 1500°, whilst the blast is heated to about 700° only. 



To remedy these evils, and seoqre a Mast of 1400 < r 1500°, 

 Mr. Cowper employs Mr. Siemens' sVegenerative furnatv BYStem, in 



