THE president's ADDRESS- 329 



great. Tlie necessity of tlie study of Hydro-dynamical laws by 

 tlie tin-dresser has been somewhat overlooked. The real points for 

 experimental examination ^Te, first, the specific gravity of the tin 

 ore (black tin) and of the gangue in which it is found ; secondly, 

 sizing, or the regulation of the flow of water to the si%e of the 

 particles which are to be retained, remembering that, the specific 

 gravity being the same, it will require a larger flow of water to 

 move a large particle than it will to move a smaller one. These 

 are points which have not been attended to with sufiicient exact- 

 ness by our tin-dressers ; at present the great cost of tin-dressing 

 is in the human labour, and in labour which is often done by 

 young and unskilled persons. It would not be difficult to con- 

 struct machinery, which should allow of stuff flowing on to it from 

 the stamps grate, and of passing onwards, over buddle after 

 buddle, frame after frame, until tin at all events fit for the ' ' burn- 

 ing house," passes off from the last table or buddle-frame. I 

 would earnestly call the attention of mine-agents to this import- 

 ant point. 



Whilst I am on the subject of economy in mine labour, allow 

 me to mention the Barrow Rock Brill, as a boring machine of 

 much value in diminishing the cost of labour. This-drill has in 

 this respect been very successful at Dolcoath mine, where it has 

 been in operation for about ten months, and that continuously 

 since the drill first used was shortened, while other drills, which 

 have been tried in various parts of Cornwall, have soon ceased 

 to work, from not having been found to be satisfactory. 



The Barrow Drill has the recommendation of being a strong, 

 portable, and handy machine, simple in construction, can be 

 worked for a small sum, and while at work it actually improves 

 the ventilation of the level. Its simplicity is in having few 

 moving parts, and it is so handy that it can be made to bear on any 

 point in the back, end, walls, or floor of the level. The rotation 

 of the borer as it works is effected by hand.* The machine itself 

 weighs, including the bed plates and gudgeon, only about 115 

 lbs., and the wrought iron bar or column for fixing the rcachine 

 for working weighs about 120 lbs. more. Some of the other 

 machines that have been tried weigh several tons. The com- 

 parative lightness of the Barrow machine is imjDortant for 



* The Borers now used are If, 1^, and 1 inch diameter. The length of stroke 

 is 4 inches, and gives 300 blows a minute. 



