APPENDIX 287 



Page 63. 



SINCE the first edition of this book has been published, 

 Prof. Dewar, in a series of three lectures at the Royal 

 Institution of Great Britain, 1 has made most instructive, 

 and fundamental experiments, by means of liquid air, 

 which may be taken as illustrating the conception given in 

 the formula fig. 5, p. 55. We propose in this Appendix 

 to explain these experiments by means of this formula. 



First we must premise the constitution of the atmo- 

 sphere. 



Air in the main consists of two classes of gaseous 

 molecules, 2 Nitrogen and Oxygen molecules. Roughly 

 speaking, there are about four times the number of 

 Nitrogen molecules to Oxygen molecules. * ^v 

 Other atomic and molecular matter exist ; ( ) 

 but they are, in volume, not of sufficient 

 importance to notice here. 



According to our view, this envelope of 

 air which surrounds the world consists of 

 free molecules, which increase in dimensions 

 (i.e. temperature) the higher we rise from 

 the surface of the earth. 



The following conveys the conception, 

 where a, in the diagram, fig. 1, represents 

 the ultimate dimensions of the molecule, 

 holding the greatest quantity of Ether, 

 and fe, a smaller molecule, holding a less 

 quantity of Ether, a, therefore, is of greater Fifr lt 



i Jan. 20th, 27th, and Feb. 3rd, 1898. 



3 It is not quite certain if the gaseous units of which the air 

 consists are atoms or molecules. In order to convey our idea simply 

 \ve will assume them to be molecules. 



