194 PHILOSOPHICAL TRANSACTIONS. [aNNO 1738. 



thus blow stronger or weaker, in regard to the velocity by which the top and 

 bottom of the bellows meet ; the blast also will last in proportion to the quan- 

 tity of air, drawn into the bellows through the valve or wind-clap. 



This happens after the same manner in our water-bellows ; for the contained 

 air cannot force itself down through the water, more than through a well- 

 secured deal-board with pitch. When the bellows are lowered down into the 

 water ; the contained air must necessarily be compressed by the water, which 

 rises alternately into the bellows A, a ; so that the air must recede, and pass 

 through the leathern tubes k, r, where it meets with the least resistance. From 

 all which it undoubtedly follows, that the larger, that is to say, the more air 

 these water-bellows are made to contain, and the greater the velocity is by 

 which they are made to descend into the water, so much greater is their effect; 

 and that the effect which they are able to perform, must be equal to that of 

 leathern or wooden bellows of the same capacity, in containing an equal quan^ 

 tityofair. in, 



As to the advantages which this new invention has over others, it is well 

 known that the power which works the common bellows, used at iron furnaces, 

 must be sufficient not only to compress the bellows, but at the same time to 

 force down the lever with its weight or counterpoise; which lever serves again 

 to raise the bellows, when the cog or button on the axle-tree of the water- 

 wheel slides off from the bellows-tree ; so that the power must be sufficient at 

 once to produce two different effects ; whereas these new water-bellows require 

 scarcely any greater power than what is necessary to overcome the friction near 

 the centre of motion, or the axis c ; for in this invention an advantage is ob- 

 tained, which very rarely happens in mechanics, viz. that the weight to be 

 moved is, on the balance in equilibrio ; since the bellows a, a cannot be other- 

 wise conceived, than as two equal, though heavy weights, in a pair of scales, 

 which balance each other, though their weight be ever so great; so that, if each 

 of these bellows should weigh a ton, they must still equiponderate ; which is so 

 much easier attained to, as it requires very little art to make them both of a 

 weight, and order them at equal distances from the centre of motion. It is 

 consequently known how small a power is required to set the scales of a balance, 

 with equal weights, in motion, notwithstanding the weight may be as great ag 

 possible ; all which may with good reason be applied to these water-bellows. 



And though it cannot be denied, but that the bellows which sinks down into 

 the water-hole or sump n, becomes so much lighter, as it loses of its weight in 

 water, by which means the water-bellows to be raised seems so much heavier, 

 as the former loses of its weight, by being let down into the water ; yet this is 

 compensated, if we consider, that the water which falls down along the sloping 



