128 ANNUAL OF SCIENTIFIC DISCOVERY. 



mixture closely approaching to a molecular combination, if indeed 

 plates so thin could be made without splitting atoms. 



The principles of capillary attraction lead to a similar result. 

 It has been proved that the dynamic value of the heat required to 

 prevent a body from cooling when stretched is rather more than 

 half the work spent in stretching it. Hence, if we calculate the 

 work required to stretch it to any extent, and multiply the result 

 by three-halves, we have an estimate, near enough for the present 

 purpose, of the augmentation of energy experienced by a liquid 

 film when stretched and kept at a constant temperature. Taking 

 .08 of a gramme weight per centimetre of breadth as the capillary 

 tension of a surface of water, and therefore .16 as that of a water 

 bubble, a quantity of water expanded to a thinness of one two- 

 hundred-millionth of a centimetre would, if its tension remained 

 constant, have more energy than the same mass of water in ordi- 

 nary condition by about 1100 times as much as suffices to warm it 

 by 1 Centigrade. This is more than enough to drive the liquid 

 into vapor. Hence, if a film of one two-hundred-millionth of a 

 centimetre can exist as a liquid at all, it is perfectly certain that it 

 cannot be many molecules in thickness. The argument from the 

 Kenetic Theory of gases leads to a similar conclusion, as do other 

 electrical measurements. The result of the series of experiments 

 first mentioned gives a certain result for the value (one four-hun- 

 dred-millionth of a centimetre) there given, and a high probabili- 

 ty that the limit is at least one two-hundred-millionth of a centi- 

 metre. 



THE CONTINUITY OF THE GASEOUS A.ND LIQUID STATES OF 



MATTER. 



Among the most important results of physical investigation 

 recently obtained, are those of Dr. Andrews, on the continuity of 

 the gaseous and liquid states of matter. 



The transition from the gaseous to the liquid state, and from 

 the liquid to the solid, has been regarded as necessarily abrupt, 

 with the exception of the plastic condition assumed by some solids 

 just before liquefaction. Dr. Andrews has shown that this is very 

 far from being the case. 



A series of experiments was undertaken by Dr. Andrews, in 

 1861, in which oxygen, hydrogen, nitrogen, carbonic oxide and 

 nitric oxide were submitted to pressures greater than had pre- 

 viously been obtained in glass tubes, and while under this pres- 

 sure they were submitted to the cold of the carbonic acid and 

 ether bath. None of these gases exhibited any appearance of 

 liquefaction, although reduced to less than one five-hundredth of 

 their ordinary volume by the combined action of cold and pres- 

 sure. A short time later a number of experiments were under- 

 taken with carbonic acid, this being liquefied under certain fixed 

 conditions of pressure and temperature. 



These, together with some later researches, form the subject of 

 the lecture of which this article is an abstract. 



In the earlier experiments Dr. Andrews found that " on par- 



