213 



TJie subjoined table gives the values Ibiiiid 



In tig. 2 are drawn (lie lines which have been constructed with 

 these values. They run asymptotical in regard to the line ^^=48. 



Fig. 2. 



It is evidejit that, for a case as the one cited here, «being equal, 

 the semi-continuous method gives much less favourable results than 

 the discontinuous one. 



Now, in some cases, however strange it may sound, it is not always 

 easy to make out which method we are dealing with. For instance, 

 "batten' work" is by no means always diseojitinuous or even semi- 

 continuous, but is often very much like the continuous method of 

 working. When tlie succession of (he concentration layers is not 

 disturbed by mechanical motion or an unfav(uiral)le form of the 



