Purnace for Ventilating Sewers. 477 
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 of 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 
abuoy. 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 woul 
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 of purifying furnaces. His 
plan is, to construct furnaces above the sewers, so that their 
may be supplied by the air of the sewers ; conse- 
_ currents of air will be made to set towards these 
urnaces 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 
€composition it will undergo in the furnace. This is a 
and no other means of forming a head of water sufficiently 
Powerful can be adopted. 
Vor. VIL—No. 1. 23 
