INTRODUCTION. 



11 



the third column or those in the fourth are employed: but of course 

 the selection should be consistent throughout. Chemists are about 

 equally divided as to the use of the two series. For many purposes the 

 O = 16 basis is the more convenient, as it gives even figures for several 

 common elements. 



Such elements as enter into the calculation of cement, plaster, lime, 

 fuel, or slag are given in black-faced type for convenience of reference. 



TABLE 3. 

 ATOMIC WEIGHTS OF ELEMENTS. 



