The Florence tribune., 1901-06-22

have been all crushed, broken and mingled with debris from the surface to the 750. No one was hurt. Forum. ately only one miner was in that part of the mine, and he had time to get out of the way of the crash before the stull- floor was broken through.
 The plant of the mine was not damaged, being on firm ground south of the main stopes. The southeran part of the mine was not affected and the mine work has since proceeded as usual. The damage is regarded as nominal. Most of the ore of the north end of the mine down to the water level at the 760 had been removed, but some broken down ore remains under the wreck.
 This extensive caving and crushing is another example out of many, of the futility of attempting to hold up mountain with timbers. Even on the Ccmstock lode. at Virginia City, with in sight almost of the superb pine for ests of the Sierra Nevadas, the trans fer of large portions of those forests to the interior of the mines in the shape of square sets, framed and set with geometrical precision, served only the temporary purpose of checking in- cipient caving of the walls and secur- ing the safety of the miners for time. But when heavy splitting off from the walls began, with crowding at one side or the other. the beautiful symme- try of the square set structure was inn paired and the posts were thrown out of the perpendicular, the structure had more the nature of trap than secure shield. So it was at the Emma, in Utah; at the Silver King and the United Verde, in Arizona, and will ever be in mines where there are large stopped spaces with walls liable to split off and fall in. It is only question of few months or years in most cases, when collapse must come and gener- ally with fatal suddenness and great loss of property and life.
 How, then, shall we work such de- posits? This is question confronting the mining engineer and requiring his best efforts for it's solution. It is not new problem, and each case has it's peculiar conditions, so that no fixed rule or method can be insisted on. There is, however, one general plan which may be adopted. If the walls are unstable and unsafe caviIg should be regarded as advantageous. Let the ground cave in and follow the extrac- tion. Do not try to hold it up. Ke- move the ore below the wreckage in such way that this wreckage shall follow slowly but surely and fill the spaces from which the ore has been re- moved. Attack the unbroken ore 1T such a way as to remove it in blocks or slices of convenient width, as in the long wall system of mining coal. O. drifts may be run at right angles just under the wreckage so as to block ou
 regular squares, one. after the other
 being removed.
 Access may be had by side drifts O
 galleries in the firm ground. Int stopes may be carried across the lode O.
 parallel with the walls. The remova
 of a small area of the solid lode doe
 not precipitate 8 run or sudden cave
 Usually the movement of the loos'
 debris is gradual and gives time fol
 the removal of broken ore. If ther
 are deads and waste these can de piled
 back as in drift mining in gold grave
 placers. This method of stoping ou
 the ore in slices may be varied as re gards the breadth of the slice and it height according to the conditions. the debris stands up well and does nc crowd the miners, broad openings ca . be made.
 { Temporary protection from the fall 7 ing of small fragments can be secure 3 by line of Jimoers or supports col ] cred by blanks or steel plates, all ( r which may be withdrawn and move . forward as the extraction proceed D Timbers or steel supports may be mad i, taperiug so as to be easily withdraw 2 from the debris of rocks and timber l Any timbers lost in the caving tend { e form mat or net work, which is l protection against rapid and sudde ,- fall of earth and stones.
 ?. The plan of filling in old stopes 1 t loose attle earth, stones or broken ros t has the disadvantage that such stu ,f runs too freely and cannot be subs l. quently underrun with the same secu a ity as 6 mass of coarse rock and tir
 Der wreckage, which moves slow 'o downwards.
 1T B. E. Denure met with a serious g IS cident in runaway to-day at moo IS He left his team standing on the soui