not otherwise pay to strip and mine. Also in every case the 

 increased use of railroad ties in open pit mining makes in the 

 aggregate amount of lumber used a large item. 



In order to more fully understand the relative basis of 

 these two methods of iron mining, we will take the figures for 

 the 1912 season which show that there was a total of 34,- 

 000,000 tons of iron ore mined and shipped from the Vermil- 

 lion, Missabe and Cuyuna ranges. Of this amount, approx- 

 imately 10,000,000 tons was mined by the underground method, 

 and 24,000,000 tons from open pits. In other words, nearly 

 oae-third of the ore mined last year was produced by under- 

 ground mining. 



To mine those 10,000,00 tons of ore a certain amount of 

 timber had to be used. This is commonly divided into two 

 classes, as, mining timber and "lagging." Mining timber is 

 nothing more or less than small logs, from six inches to ten 

 or twelve inches at the small or top ends and of usual log 

 lengths, of tamarack, spruce or jack pine. This timber is 

 used in what is termed "sets." That is, for cribbing up the 

 sides and tops of the lateral shafts, or "stopes," and on all 

 four sides of the vertical shafts, thereby protecting the lives 

 of the men employed from falling rocks and cave-ins and thus 

 rendering the mines safer to work in. This must be carried 

 on at all times as the work and mining progresses. It is 

 practically all ruined by blasting before the "stopes" are 

 abandoned so that none is re-used. 



To define "lagging" so that it will be easily understood, one 

 may call it "poor cord wood." It is cut from all of the smaller 

 standing timter and the tops of the trees that the mining tim- 

 ber has been made from and trimmed down to two or three 

 inches. All kinds of timber goes into this, such as cedar, birch, 

 tamarack, jack pine, spruce and balsam, green, dead or fire 

 killed. "Lagging" is cut six feet long. The large pieces are 

 split and the smaller ones are left round. This is used in 

 the tops of the working ends of the "stopes," both to protect 

 the lives of the miners and to separate the iron ore from the 

 overburden or ground when the blasts are set off and the 

 mass comes down. Consequently all of this is broken up at 

 every setting and must be replaced with new material each 

 time. Therefore a great deal of this is used. This explains 

 briefly what timber is used for in underground mining and 

 the necessity for it in carrying on the work. 



[18) 



