OF ARTS AND SCIENCES. 139 



In writing these formulas I have assumed that all the acids are 

 12-basic, smce it has been shown that there are salts of the sixteen-, 

 eighteen-, and twenty-atom series which correspond with this view. 

 I shall resume the discussion of the subject in connection with the 

 phospho-moljbdates, and at the same time examine in detail the ques- 

 tion of the existence of a distinct class of pyro-salts of the tungstic 

 and moljbdic series. 



i^To be continued.) 



