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sink the pistons two inches, and four tltnes that 
weight, or 11801b. to sink them three inches, and 
upwards of a tun weight to bring them ^ an inch 
lower ; in every case the spring would continue to 
act with a force proportionate to the pressure. If a 
greater motion in the spring is required, let the 
tubes be deeper. If 8 inches deep the motion un¬ 
der equal pressure, will be the double of those I 
have mentioned. There are various ways in which 
these springs may be adapted to carriages. Of 
these, perhaps the cheapest, and the best, would 
be, two planks united by leather dressed in oil, 
and covered with elastick gum, so as to be perfect¬ 
ly air tight. For a chair, four bladders soaked in 
oil and covered whh strong leather, in the way of a 
foot ball, would make a cheap and excellent spring. 
The leather should be put on before the bladder is 
blown up, so that it may be smaller than the blad¬ 
der, and press them strongly in every part ; this 
would keep them from breaking or loosing any air 
when strained. These balls should be confined in 
boxes, that fit to their lower diameters, and over 
tliese the thorough braces that hold the chair should 
pass, and be fastened to the bars before and behind 
the chair ; this would not only render such a car¬ 
riage much lighter than those now in use, but by 
simplifying the machinery under it, also much 
cheaper. You will judge of the utility of my in¬ 
vention by an experiment I have already made. In 
travelling from Paris to Naples, we were three of 
us, with oiiicli baggage in my coach ; my springs 
