The decision to sink the No. 3 Shaft was made because the increasing depth and northerly pitch of the orebody made the extraction of the ore from the lower levels through the present main shaft increasingly difficult and costly.Another factor was the necessity for improved ventilation of the lower levels. The high rock temperature gra:dient of about 10 F. per 72 ft. of depth will probably, in the future, necessitate some form of refrigeration to cool the air drawn into the mine and provision has been made for this should it become necessary.