HAYES. — ERRORS IN COOUNG CURVES. 



19 



beam of light to fall upon the disc ; and whenever a slit in the disc 

 moves across this beam of light a momentary Hash passes into Si. By 

 var}'ing the number of slits in the disc, the period between flashes can 

 be made nearly any length between one second and one minute. 



Fig. 6. 



Fig. 7. 



Fig. 8. 



The Heating Part of the Apparatus. 



The copper block and thermo-couples. — The heating part of the ap- 

 paratus may be briefly described with the aid of Figures S and 9. 

 Figure H repre.sents the cross-section of a copper cylinder five inches 

 lung and three inches in diameter. Two holes, each three inches deep, 

 are synmietrically drilled in the top of the cylinder. These holes have 

 a diameter nearly one millimeter greater than the diameter of the pro- 

 tection tube tu be experimented upon. A protection tube is placed in 

 each of the holes in order that the heat capacity may be the same for 

 each. One of these tubes is closed at the lower end and the other one 

 left open. Within the closed tube an ordinary copper-coustantan 



