JFurnacefor Ventilating Sewers. 177 



with which, the boat may be made to ascend will be as the 

 difference between the surface of the paddles, and the 

 transverse section. Consequently it may be increased at 

 pleasure by increasing the surface of the paddles. The 

 force thus obtained may be employed in moving a tow-boat 

 (and in this way a heavy-loaded river boat, seventy feet 

 long, and a canoe almost as large, were moved against the 

 current almost with the facility o( the tow-boat alone) ; or 

 the machinery may be attached to the common river-boats, 

 (as it will be no great incumbrance) and nothing more will 

 be necessary than to fasten the rope around the windlass, at 

 the foot of the rapids, where the rope may be sustained by 

 a buoy. The same rope may be made to move several 

 boats at the same time, each furnished with the proper ma- 

 chinery. A chain would be preferable to a rope, as it would 

 wear less, and would oxidate very slowly under water. 



6. Furnace for Ventilating Sewers. 



Mr. R. Bulkley has recently proposed, in a memorial to 

 the Mayor and Common Council of New-York, to remove 

 the foul air of sewers by means o( purifying furnaces. His 

 plan is, to construct furnaces above the sewers, so that their 

 draft may be supplied by the air of the sewers ; conse- 

 quently currents of air will be made to set towards these 

 furnaces through the openings of the sewers, instead of the 

 exhalations which now escape from them. The air of the 

 sewers will have to pass through the fire and the chimney of 

 the furnace before it can mix with the atmosphere; of 

 course it will be deprived of its noxious properties by the 

 decomposition it will undergo in the furnace. This is a 

 subject of no little importance, since these exhalations when 

 concentrated have been known to kill instantly, and when 

 more diluted to cause malignant fevers, particularly around 

 the openings of the sewers. Mr. B. contends that no other 

 effective plan of removing the evil can be devised since the 

 tide waters cannot be depended upon for cleansing the sew- 

 ers, on account of the small rise of the tides, (only five feet) 

 and no other means of forming a head of water sufficiently 

 powerful can be adopted. 



Vol. VII.— No. 1. 23 



