Advantage of using tripod drills for unsound rock.... Use of tripod drills where rock contains pockets of clay- Arrangement of churn drill holes for multiple shots. Advantage of flat-lying beds_-_ Difficulties encountered in steeply inclined beds___ 37 37 37 37 38 40 41 42 42 42 42 43 43 43 43 43 44 Use of different grades of explosives in same drill hole__ 70 Examples of shots in which detonating fuse was em- General considerations in blasting_. 87 91 Proper balance between explosive cost and drilling cost__ Proper balance between size of blast and size of steam Secondary blasting_. Definition of secondary blasting___. Conditions governing the extent of secondary blasting___. Advantages of "block-holing" over 46 mud-capping" method_ Method of block-hole blasting 95 Circumstances that justify the mud-capping method__. Examples of excessive secondary blasting costs-_-_ Examples illustrating blasting efficiency_ Examples of quarry costs____ Blasting records____ Importance of keeping records___. 96 97 97 100 100 101 Examples of blasting records_. Safety in blasting__. 102 106 Desirability of changing from hand methods to steam-shovel 120 Solution of difficulties in changing from hand-loading to 120 Need of improved processes of mixing raw materials.. Mixing processes in cement plants---- Dry processes Typical examples of dry processes_ The semiwet process... Description of the process_ The advantages of the semiwet process_ Desirability of proper plant design___. Economic conditions---- Conditions governing plant location_. Transportation. Fuel 139 140 140 140 141 141 142 142 144 144 145 145 146 146 147 148 148 148 149 149 149 Publications that may be obtained only through the Superintendent of Documents 151 TABLES. 8 TABLE 1 Total recorded production of principal hydraulic cements in 2. Production, in barrels, and percentage of total output of Port- 3. Kind of rock, number, depth, and arrangement of churn drill 4. Compositions of 40 per cent and 60 per cent "straight" nitro- |