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124. has passed the Cagniard de la Tour point or not is not known, and therefore it cannot well be anticipated whether the coming on of that state sooner or later with particular bodies will influence them in relation to the more general law referred to above.

The law already suggested gives great encouragement to the continuance of those efforts which are directed to the condensation of oxygen, hydrogen and nitrogen, by the attainment and application of lower temperatures than those yet applied. If to reduce carbonic acid from the pressure of two atmospheres to that of one, we require to abstract only about half the number of degrees that is necessary to produce the same effect with sulphurous acid, it is to be expected that a far less abstraction will suffice to produce the same effect with nitrogen or hydrogen, so that further diminution of temperature and improved apparatus for pressure may very well be expected to give us these bodies in the liquid or solid state.

Royal Institution, Feb. 19, 1845.

Historical Statement respecting the Liquefaction of Gases.

not aware at the time when I first observed the liquefaction of chlorine gas, nor until very lately, that any of the class of bodies called gases, had been reduced into the fluid form; but having during the last few weeks ought for instances where such results might have been afforded without the knowledge of the experimenter, I was surprised to find several recorded cases. I have thought it right therefore to bring these cases together, and only justice to endeavour to secure for them a more general attention than they appear as yet to have gained. I shall notice in chronological order, the fruitless, as well as the successful attempts, and those which probably occurred without being observed, as well as those which were remarked and described as such.

Carbonic Acid, &c.—The 'Philosophical Transactions' for 1797 contain, p. 222, an account of experiments made by Count Rumford, to determine the force of fired gunpowder.