308 PHILOSOPHY OF STORMS. 



it passes, and thus to know how much the barometer will 

 fall under the centre of the. ascending column, and how much 

 it will rise all round the column by the rapid outspreading 

 of the air above. Data for making these several calcula- 

 tions are known proximately, and may be stated very briefly 

 as follows. 



1. The decrease of temperature in ascending in the at- 

 mosphere. 



2. The diminution of pressure which the ascending cur- 

 rent experiences at all heights in its ascent. 



3. The degree of cold produced by that diminished pressure. 



4. The quantity of vapor in the air at the surface of the 

 earth, from which the npmoving column is supplied. 



5. The number of degrees the dew point is below the 

 temperature of the air at the time. 



6. The height to which the air will ascend before it be- 

 gins to form cloud from the cold of diminished pressure. 



7. The quantity of vapor which will be condensed by 

 this cold, at all heights to which the current ascends. 



8. The quantity of latent caloric of elasticity evolved by 

 the vapor thus condensed. 



9. The quantity of latent caloric of fluidity evolved by 

 the vapor thus condensed in case of hail or snow. 



10. The specific caloric of air at different densities. 



11. The number of degrees the air would be heated, or 

 rather prevented from being cooled, in its upward motion, 

 by the caloric of elasticity, and caloric of fluidity thus given 

 out. 



12. The diminution of the specific gravity of the air 

 in the cloud, produced by the evolution of this latent 

 caloric. 



13. The height to which the air will ascend before all 

 the vapor is condensed which can be condensed by the cold 

 of diminished pressure. 



14. The quantity of space left unoccupied by the con- 



