TRANSACTIONS OF THE SECTIONS. 171 
Pollock and Govan Railway near Glasgow, who had thus anticipated both Mr. Ste- 
phenson and Dr. Guyot. 
On some proposed Improvements in Valves, Stopcocks or Stoppers for regu- 
lating the Passage of Fluids, by the Use of Flexible Substances. By 
Georce BucHanaNn, F.R.S.E., Civil Engineer. 
The author adverted to the great importance of this subject in practical mechanics, 
affecting essentially all the arrangements for the supply of water to our cities and 
dwellings, and for the regulating.and feeding of our water cisterns, our ordinary 
boilers for hot water as well as the boilers of steam-engines, and also in the safety- 
valves and other valves of steam-engines, and in gas-works ; a wide field, but only 
into a small portion of which he meant to enter at present. Considering however 
the skill and perfection already attained by our engineers, and the many improve- 
ments introduced by eminent scientific and practical men, he might well feel diffident 
in bringing before the Association anything out of the usual course of practice, and 
could only plead the important and interesting nature of the subject, should the 
views not prove of practical value in themselves. 
The first improvement, and which applies to all valves of the lifting kind, conical 
or flat, and to the stoppers of bottles, consists in the introduction and use of a flexible 
substance, as vulcanized India-rubber, to form one of the bearing surfaces of the 
valve ; and this not as a washer in the usual way, but in the form of a distended mem- 
brane, stretched across the mouth of an opening or cavity formed in the centre or 
round the circumference of the lid of the valve. This opening or cavity is of larger 
diameter than that of the valve orifice, so that when the orifice is brought to press 
against the membrane, this latter presents, by its smooth and even surface and by 
its tension and great elasticity, the means of producing with facility a perfect contact 
with the metallic glass or other surface, to the exclusion of the fluid, and sealing the 
orifice by simpler means than any hitherto in use. The cavity behind the membrane 
may be either open or shut; if open, the pressure against the orifice of the valve in 
closing is resisted by the membrane, but in such a way that the elasticity and tension 
of all its parts are brought into action; different from the case of a washer, where 
the narrow bearing surface is only affected, compressing a thin ring of the soft ma- 
terial against the metal, while here the pressure is diffused over the whole surface, 
every particle of which is brought into play, and the substance thereby less liable to 
tear and wear and derangement. If the cavity behind the membrane be shut, then 
the pressure of the valve orifice is resisted, both by the elasticity of the membrane 
and by the confined air behind, presenting a sort of cushion of resistance, and along 
with the air, water or other fluid, is sometimes introduced as a fluid cushion. 
The bearing surface should be narrow, and so far indeed as the contact is con- 
cerned and the exclusion of the fluid, it may be reduced to a very thin edge; for 
Mr. Buchanan had found by various experiments that it is not so much the breadth 
of the surfaces in contact as their mutual pressure, on which the effect of excluding 
the fluid depends ; and the narrower therefore the surface is made, the greater is the 
intensity of any given pressure. 
Such is the principle of this first improvement upon valves, and so far as experience 
had gone the result was very satisfactory. He had found the vulcanized India-rubber 
to retain its form and tension for along period unimpaired. If applied loosely, the form 
was liable to change by pressure, but in the form of a distended membrane it re- 
tained its form and elasticity in a surprising manner, and this both with air and water. 
With hot water and steam of a moderate pressure, he had also reason to think it. 
-would answer, but had not tested it for sufficient Jength of time to speak decisively. 
The distension of the membrane he had contrived to produce in a very simple manner, 
by joining round the circumference of the membrane or disc previous to distension 
another similar disc with an opening in the centre, or-else a thickish ring, and then 
by applying a metallic ring of larger diameter than the membrane the required dis- 
tension was easily effected. 
Mr. Buchanan then illustrated the application by various experiments and models, 
and its peculiar adaptation in all cases of regulating the level of fluids where the ope- 
ration to be effected depends on a nice balance of forces ; and he had applied it suc- 
cessfully in this way as a ball-cock or regulating valve for cisterns, and also for hot 
