204 THE JIINERS' FRIEND. 



worse, hj ttcenti/ or thirty years Use in any Force-work, 

 where constantly worked, and where they Rise and Fall 

 twenty times oftener than my Valves will do. 



Miner. But what think you, Sir, if you should meet with 

 such Corrosive Water in some of our Mines, as will in a little 

 time eat throug'h your Copper Vessels. 



Author. Truly Sir, this Question does a little startle me, 

 because I never expected to meet any Water of such a 

 Corrosive quality in any Mine : And could I find out a Mi^ie, 

 whose icater abounds with such Acid Particles, as to Destroy 

 or Injure the Copper Vessels of my Engine, I would Drain 

 that Mine for nothing but the ivater I shall take up ; because 

 the water wovild be more valuable than any Oar (I believe) 

 in England. And were there even a tenth part of Aqua 

 Fortis to nine Tenths of Common water., which is impossible 

 to suppo.se it should be ; I say, such a water could have no 

 Effect on the Coppers., were that water to lodge some time in 

 the Copper Vessels, much less in passing through them with 

 that Celerity and Rapid motion that always acpanies (ivV) it. 



Miner. But Sir, will not such a Continual Fire, as must 

 be kept under your Boylers, hum them out in two or thre 

 Months time, and spoil the Work of your Engine. 



Author. I can assure you they will not Decay in some 

 years, (unless some Fellow be hired or imployed on purpose 

 to do it. And should any Villain be imployed to hum, break, 

 or Destroy any of the Engines now used in your Works for 

 liaising of Water, we are then on the same Level with you 

 in that point. But I will give you one Reason why my 

 Engines will not easily Decay, and I am sure that will go 

 further with yoii than all the Affirmation I can make. For 

 first of all, Although a white Heat will melt Copper, and a 

 red Heat, and sudden cooling it again, will Scale the Copper, 

 yet such a Heat as is possible for it to have or suffer while 

 Water is in the Boyler, can have no ill Effect, or cause any 

 Alteration in our Copper. A Friend of mine has Coppers 

 used in Sugar Boyling of twenty years standing. They may 

 be a small matter worn with cleaning on the Inside, whereas 

 on the Outside there does not appear the least visible Decay : 

 For as soon as the Fire has thrown a thin Coat of Soot on 



