682 Boring Operations in Fort William^ [No. 103. 



one of the connecting joints, 160 feet from the surface, the remaining 

 320 feet attached to the jumper, being left within the bore. 



Under these circumstances the only hope of being able to con- 

 tinue the operations lay in the practicability of unscrewing and 

 raising the rods, and this after much difficulty was at length so far 

 satisfactorily effected by the use of an ingenious instrument designed 

 by Captain John Thomson, that 29(^ of the 320 feet of the rods 

 were successfully extracted. This instrument consisted of three 

 steel arms rivetted to an iron bell, in the manner shewn in sketch 

 No. Ill, and subsequently welded to the end of the undermost 

 boring rod. The interior surfaces of the steel arms were cut in 

 grooves so inclined, that on the head of the rod to be extracted 

 being grasped within them, and a rotatory motion communicated to 

 the instrument from above, the teeth cut into the soft iron, and by 

 the hold thus obtained, the unscrewing and raising were effected. 

 The bell acted as a guide, and was made of diameter just sufficient to 

 admit of the instrument being readily worked within the tubing. It 

 became necessary to pass iron pins through all the connecting joints 

 of the rods, otherwise the rotatory motion would have unscrewed 

 them. 



On the 16th of February, 1839, the instrument above described 

 was again successfully employed in unscrewing twenty feet more of 

 the fractured rods. After this a single rod, only ten feet in length, 

 remained attached to the jumper, and repeated attempts were made to 

 effect its extrication, till at length during one of these, its joint 

 unfortunately broke off, leaving the difficulty greater than ever. The 

 only remedy which presented itself, was to construct a second instru- 

 ment of which the steel arms would be long enough to lay hold of the 

 shoulder strap in the centre of the rod. This instrupient, after 

 several unsuccessful attempts had been made with it to unscrew the 

 broken rod, also gave way, the upper part appearing with one arm 

 attached to it, while the other two arms attached to the bell remained 

 below. By the use of the conical worm auger the broken instrument 

 was occasionally raised as high as thirty feet, but the hold of it could 

 never be retained to any greater height, some obstacle to its further 

 progress upwards invariably meeting it there, and effectually prevent- 

 ing its removal. 



