and Contraction of Building Stones. Wt 



in part to imperfections in the measuring apparatus ; but as the 

 hygrometric state of the stone was not recorded, we can take no 

 account of it in our deductions. These discrepancies, however, 

 will have but Httle effect upon the general result, for it will be 

 observed that there is always an increase in the length of stone 

 for an increase of temperature, when any two experiments are 

 considered which are removed from each other by several de- 

 grees. 



From the facts ascertained concerning the expansion of other 

 substances, we may assume that the expansion of stone is uni- 

 form ; and that, within the range of our experiments, each of 

 the stones increased in length by a common difference for each 

 degree of the thermometer. To find an approximate value for 

 this common difference, say for the granite, we substract the 

 first observed length from the last, and, if these experiments 

 were accurate, the difference .0470 would be ninety-six times 

 the common difference, ninety-six being the difference in degrees 

 between the extreme temperatures : the same operation being 

 performed with the second experiment, and that next the last ; 

 the difference .0298 (the difference in lengths) should be eighty- 

 six times the common difference. By thus comparing the ex- 

 treme experiments of those which remain, we obtain the follow- 

 ing Table. 



u2 



