290 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 51 



directly from the diagram not only the work done but also, with but 

 little trouble, the increase or diminution of heat. 



The altitude above the earth's surface does not enter into the 

 formulae and graphic diagrams used in this method of treatment, a 

 circumstance that is of great importance for the complete under- 

 standing of meteorological processes. From this we can conclude 

 that such changes of temperature as accompany the ascent or 

 descent of the air are not to be referred back to the work of eleva- 

 tion, but are conditioned only by the changes of atmospheric pres- 

 sure associated with the change of altitude. If this view had been 

 properly considered earlier, one would never have accepted the 

 erroneous idea that the cooling in ascending currents is a conse- 

 quence of the work done in elevating the air. 



Notwithstanding all this, it does not seem advisable to make use 

 of this method in the present memoir since it demands an abstrac- 

 tion too great to suit the new ideas that are immediately press- 

 ing for attention. 



If we wish to consider the conditions in a vertical column of 

 air then the altitude of any point above the surface of the earth 

 is the determining item that seems to us especially characteristic. 

 Even if we know that the atmospheric pressure diminishes with the 

 altitude, still this pressure makes no such direct impression on our 

 senses as does the altitude. 



If we introduce the altitude as one of the coordinates then we 

 more appropriately choose it as the ordinate, while the other ele- 

 ment whose relation to the altitude is to be presented should be 

 laid off as abscissa. 



It is evident that this method of presentation can be applied not 

 only to the temperature but to all meteorological elements that 

 have any relation whatever to the altitude, such as the pressure, 

 moisture, electric potential, etc. 



If the curve of temperature is plotted in this way, then we obtain 

 the diagram that W. M. Davis has used (with only a change imposed 

 by the English system of measures), and from which he has drawn a 

 system of consequences, to which I also had arrived somewhat 

 earlier by another method and which I have developed quite recently 

 in the above-mentioned memoir (of May 5, 1898) from a different 

 point of view. 



In the present memoir the last mentioned style of presentation 

 is always used and the metric units of i° C. and 100 meters of alti- 

 tude are represented by the same equal distances measured along the 

 axes of abscissas and ordinates, respectively. This offers the great 



