340 Dr. Ure’s new experimental researches 
able to determine, with great precision, the elastic forces of 
vapours at any temperature, from zero of Fahrenheit, to a 
much higher degree of heat than even Betancourt seems 
to have reached. The experiments were made soon after 
that time, but circumstances have till now prevented me from 
arranging them for publication. 
With Betancourt's apparatus I am not acquainted, 
having seen only the brief table of results, inserted in our 
systematical works on chemistry. Professor Robison’s con- 
sisted of a strong boiler or digester, containing the water, 
and furnished with three small apertures; the first receiving 
the bulb of a thermometer, the second covered with a safety 
valve, and the third having a barometer tube attached. At 
first I used a similar construction, but finding it hazardous, 
and somewhat unmanageable in the high heats, and difficult 
to render air tight in the lower temperatures, I abandoned it, 
after some unsatisfactory trials. At the low degrees of heat, 
the vacant part of the barometer tube introduces errors, since 
it has not the temperature of the boiler; and the bulb of the 
barometer, used in high heats, occasions a similar fallacy in 
the determination of the true elasticities. 
Still, however, it was ingeniously conceived, and the results 
furnish good approximations, creditable to the celebrated 
experimenter.* They agree nearly with those of Betan- 
court, being obtained probably in a similar way. The method 
adopted by Mr. Dalton, is recommended by an elegant 
simplicity. It is merely a common barometer, into which a 
little of the vapour-giving liquid is introduced, so as to 
moisten, and float above the mercury. The vapour which is 
* See Encyclopaedia Brkannica, vol. xvii. p. 739, ad Edition. 
