Bisbee daily review., 1903-04-18
CONCENTRATES.

Tn many mines sk1ps for baillrg are preferred to pumps, as being more economical. They may be run tandem where there is room in the head frame, and where this is possible a large amount of water can be handled cheaply.
 The presence of sulphuric acid in water may be detected by the use oi blue litimus paper, which it turns red. Barium chloride is also used to detect sulphuric acid. When barium chloride is added to water containing sulphuric acid an insoluble precipitate is formed (barium sulphate).
 ! Mill tailings are not usually suitable in the making of concrete, as they gen. erally contain sulphide minerals, which on oxidizaticn will tend to disintegrate the mass. Moreover, they are usually too fine. A ccarser sand is better for the purpose, and can be obtained by screening creek sand.
 Actual or brake horse power is the power the engine develops for use; | indicated horse power depends, in fact upon the efficiency of the engine. Nom inal horse power is usually understood to mean the power developed with sufh cient surplus to enable the engine tc continuously run at that load i A retaining wall can be made stronger if the several courses are laii so as to have an inclination inward toward the bank it is to support. The base of the wall should also be broader than the upper portion of the wall Where rock is to be supported, often dry wall will answer as well as ma sorry.
 The Dalmatia mine in Kelsey dis trict, Fl Dorado county. California, in 1888, is believed to have been the first mine to be equipped with electric pow CT in that state Water from Rock creek ditch was utilized to drive a Pel ton wheel, which ran dynamo of 12t H. P. The current was transmitted one mile to the Dalmatia works and one and a half miles beyond to the Gopher Boulder.
 Gilsonite, which is also caled uintah ite, is a hydro-carbon compound, occur ring near Fort Duchesre, Utah. It js brittle and has a black color with 8 brilliant luster. It fuses readily ir the flame of candle, and burns like sealing wax Eaterite is a soft hy- drocarbon compound, being elastic bitumen, resembling india rubber. and of considerable commercial value. 1 It is not always possible to identify a surface rock that has been much altered by oxidizirg. though familiarity with certain rocks makes it more easy to recognize them. Diorite and cia !. base. hard. tough rocks when in nor nal condition, often weather to soft decompoSed masses of brownish color wholly unlike the original rock; yet miners familiar with both are noi likely to be mistaken.
 There are in California seyera thousand Chinese laoorers. some oi whom find employment in she mines but of these comparatively few are employed by American companies The greater number work for Chinese companies or individuals, or work ir placer mines for themselves Th5 total number of Chinese thus em ployed, however, does not probably exceed 5000 cut of total of 1s,0e' miners in the state. Of these vers few work underground. being mostly l employed in the large hydraulic nine in the northern counties.
 A small machine drill will not cut as many feet in hard ground in given time as a large one, but ;he cost oi operating a small rnachire. for wages consumption of air. cost Of repairs etc, often make drilling with the smaller machine really less expensive than with the large ones. and the gen eral result more satisfactory in under ground mining operations- In driving tunnels of large size thro"gh hard rock. and in extensive quarry work the larger drills are preferred and do cheaper work