128 Sir FredericJ: BmrniceU [May 19, 



is this — that the cuttings being continuously produced, can "be readily 

 carried away by a simple apparatus, a travelling chain of scoops (for 

 which room can be found between the machine and the sides of the 

 excavation), and can be poured, as produced, into waggons waiting 

 to convey them away. In this manner the operation and the pro- 

 gression of the machine may be continuous — with one qualification 

 however — the machine stands upon a bed, along which bed it is 

 capable of forward motion proportioned to the progress made at each 

 revolution ; but of course the time comes when after the machine has 

 gone forward to the extent limited by the bed, the end of its travel 

 is, for the time, reached, and then it is necessary to stop the machine, 

 and uphold it, while the bed is moved forward underneath to give it 

 a fresh point of support for a renewed start upon its journey. With 

 this exception however, the advance is, as I have said, continuous. 



XoTv although by the employment of machinery we can, by suit- 

 able appliances, make an excavation of almost any figure that may be 

 needed, there is no doubt that the plain circle form is the one which 

 of all others can be the most readily carried out, as for such a shape 

 nothing more is required than a revolving arm, or arms, carrying the 

 cutters upon the face, making thereby an absolutely cylindrical hole 

 of the size of the diameter of the arm. One of the working cutters 

 for the 7-foot hole, which is the size of the trial heading, is now 

 before you. 



I may mention, to show the way in which the excavation in this 

 material retains its figure without alteration, that the part first cut out 

 of the trial heading many months ago, is now as truly cylindrical, 

 and is as accurately of the same dimensions, as it was the very day it 

 was made ; no change of shape has taken place ; in fact, the polish 

 left by the cutter remains upon the circumference. 



I am aware that some comments have been made as to the 

 difficulty of getting rid of the quantity of stuff as fast as it is cut, 

 especially, it is said, if it be borne in mind that at the same time 

 materials may have to be taken into the tunnel, for the purpose of 

 lining it, and it is suggested that this, if a difficulty at the outset, and 

 near the ends of the tunnel, will be an increasing difficulty as the 

 tunnel progresses, and the distance to the working face therefore 

 increases. 



I will deal at once with this last state of things. Supposing that 

 trains of waggons may work within any stipulated distance the one 

 from the other, say for instance a quarter of a mile, it is obvious 

 that after the tunnel has attained a length of a quarter of a mile, you 

 may then establish a second train, to be running on the rails at the 

 same time as the first one, and when the tunnel has advanced half a 

 mile you may establish a third train, and so on ; that is to say, as you 

 attain each successive distance, such as you have determined shall be 

 that which ought to be preserved between the trains, you may then 

 provide another train. 



Those who raise this difficulty do not appear to see that it does 



