240 William E. Ford, 



However, on the assumption that the change in molecular 

 volume is uniform for the entire series the average of all the dif- 

 ferences between the measured and calculated specific gravities, 

 as given in column V of the table, is .026 or whert the signs are 

 considered, — .005. Considering the complexity of the problem 

 and recognizing the fact that the changes in the specific gravity 

 are not only due to the variation in percentages of the normal 

 dolomite molecule present, but must also depend upon the pos- 

 sible variation in the amounts of the different isomorphous mole- 

 cules, it is felt that the agreement between the calculated and 

 measured values is, in general, surprisingly close. 



From this it is seen that, whatever may be the true explanation 

 of the physical changes involved in the chemical progression of 

 dolomite, it is possible from its analysis to calculate closely what 



the specific gravity of a given specimen should be. Table VI 

 gives the necessary data for making such calculations. In prac- 

 tice it has been found that with a number of problems to be 

 calculated, it was simpler to obtain the required values by graph- 



