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THE POPULAR SCIENCE MONTHLY. 



the brake, and a third on the grating outside to handle the sinker 

 and instruments and to guide the wire as it passes overboard ; a 

 machinist is at the hoisting engine, and the recorder takes a posi- 

 tion for reading the register. When the sinker is let go, the ves- 

 sel is manoeuvred so as to keep the wire vertical, and the friction 

 line is adjusted so as to allow it to descend from seventy to one 

 hundred fathoms per minute. The instant the sinker strikes bot- 





I'U. 



-Sol NuiM, ; The Sinker going down. 



tom, which is unmistakably indicated by the sudden release of 

 the wire from strain, the reel is stopped by the friction line and 

 brake ; the recorder notes the number of turns of the reel indi- 

 cated by the register and determines the depth ; the cranks are 

 shipped and sufficient wire is hove in by hand to allow the end of 

 the sounding rod to clear the bottom. Steam is then admitted to 

 the cylinder of the hoisting engine, and the wire is reeled in slowly 

 at first but finally at the rate of one hundred to one hundred and 

 fifty fathoms per minute. The last ten fathoms are reeled in by 

 hand, then the thermometer is read and the specimen of the bot- 

 tom soil brought up in the sounding cylinder is examined. 



