AT FREIBERG. 



407 



true that you can follow any product on which you happen to alight, and find out one line 

 of main products through which the ore has been transformed to that particular one, but 

 to understand even what other agencies have had their influence in the formation of 

 the substance, you must consult either the text of the chart (in the few cases where 

 such explanation is given) or some more detailed work on the Freiberg processes ; and 

 in addition to this defect it is not always easy when practically the same substance 

 (as Raw Lead, &c), resulting from different operations, is scattered in a dozen places on 

 the " tree" to find that which is required. Again, it is not easy to follow the processes 

 analytically as in their actual sequence, for the reason indicated before, that but one of 

 the many products is selected as the most important in every line, and these lines sepa- 

 rate one set of products from the others with which they are mixed for their further 

 treatment. Another objection to it is, that it only mentions the composition of the 

 charges in the most important cases, and leaves those reagents which are not ores, en- 

 tirely out of consideration; and another, that no other but pyro-chemical processes are 

 given, and not all of these. In the substitute which I propose for this •' tree," the 

 attempt has been made to attain to a system which, while it represents the actual se- 

 quence and co-sequence of processes, permits an empirical view of these which it requires 

 but little technical information to understand. 



