IO2 Notes on the Use of the Formulas 



peculiar to heating apparatus ; in all practical applications of 

 theory, the calculations always depend on certain given quanti- 

 ties or conditions which are never more than approximately 

 known, and every apparatus or machine, for whatever purpose it 

 may be destined, should possess an excess of power or of strength 

 designed to cover the uncertainties of calculation, or to satisfy 

 exceptional circumstances. 



