Bisbee daily review., 1906-06-10
AIR BLASTS ]" IN ATLANTIC
 MINE
Are Becoming More Numerous and of Greater intensity Than Formerly Experienced in Mine.
Similar Occurrences to Those at Atlantic Have Been Re- corded in New South Wales and India.
Especial CorrespondenceD

Especial Correspondence.)
 CALUMEr, Mlcn., June I.-"Air blasts" more numerous and of greater Intensity than formerly experienced, occurred thls week in the Atlantic mine. These disturbances have been nUoed al lne AtlanIic Tor the last two years, but they have become more nu- lnerous and of greater force in the last few weeks. Owing to the hang inS wall seCUlng to sucn an extent that the sidps could not be operated, all lrIninS worK was uisconunued aDouC three weeNs ago, and every available nan put to woFk on the re-timberinS l and re-opening of the shafts. Produc- tlCn was discontinued ana tAe mil cIosSd. The disturbances of the past few days have been the rnost violent that the Atlantic has experienced and naturally caused considerable alarm tO the residents Of the mining section. 1 The force Of the shocks was felt five . and six miles from the property.
 Disturbances resulting from .'alr | blasts form an interesting subject. the ore 50 because it is not we'll under stood. Similar occurrences to those at the Atlantic underground have been lCcoTded in the Hillgrove district, New | South Wales, and in the MysoTe mines, in India. These "air blasts are not iii reality explosions. They are due to the bursting of rock under great pressure and the disturbance to the
 air of thu mine produced by the shock Eof disruption In mines where the rock is under particular strain by iee-
 son of big cavities created by stoping, causing large masses of ground to cS- isc under unbalanced stress, the "air blasts" are more frequent. It is con- non practice to. support the hanging i wall by means of portions of lode l which, are left standing, to do duty as pillars. When the pressure from
 above becomes too great for these pillars to hold the ground, they do not
 yield gently, but, like a cubical block
 UT der a testing machine, they break
 suddenly with explosive violence,
 AS F. V. Sperr. professor of mining
 iI che Michigan College of Mines has pointed out. the bursting force IS due [" external and not internal condi-
 tens. When the pressure has become
 more than the pillar of lode rock can
 bear and +he moment of rupture has
 arrived, even the scratch of a pick
 will precipitate a crash. In mines
 where the rock will not stand and the
 walls settle slowly, so IS to fin the excavations made by stoping, there are no air blasts or disturbances Of that nature. When large Areas e5 root which are left hanging nnaiIV laIl, they act like a piston and force the air out of the old stopes with all . the violence of a gas explosion.
 The large explosions in the Atlantic and which were quite pronouncsd in : the Quincy recently, are due to shs sanie Nenerai cause, and that is gen. erai condition Of strain due to 1he re- moyal of rock by mining. It js renortaa that the disturbances a. Hiiisrovs New South Wales, have gained in se.
 verify as the mine has deepened. In
 the neighboring Sunlight mine. these
 troubles are no. known, as tht vork.
 ings are in slate of a more yfeIdina
 character
 In the case Of wide lodes, such as
 the amygdaloid copper bearing forma-
 lions in the Lake Superior district tim
 Der IS used very sparingg, and pii- iars are left to support the old work
 hgs- There i3 nothing % prevent such troublesome consequences as ar
 blasts, and hence the anaoyence. with |, rassible danger, due to them .s sure.
 10 increase as the strains in the rock become greater through the extension
 Of the mine workings, both deeper and lateralIy.
 At tho Atlantic mine d. surface cracked considerably near No. 4. an
 old shaft which was abandoned a num-
 Der of years ago. Two large caye-ins occurred in that vicinity, one hole being 10 by. 15 feet, and the other slightly smaller. Numerous cracks appeared in the earth, so,re two to
 six incnes wide. Tn this connection
 t is interesting 10 1oss that the usual
 supply of water for domestic purposes
 has failed the residents. Wells which
 were in use for years are now abso-
 luieIy d-y The Assures which have j opened in the Fock undoubtedly
 drained the wells. fn some places the
 rnilroad tracks are 5adIy twisted and the ties lifted ogr of the ground.
 While the explosions in .he { ian
 tic have caused Q serious impairment ! of the mines earning powers, y, is ! gratifying to note that no fata ties
 have resulted. In the last dis, arb 1 (ContiHued on Pag. 14)