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COUNT RUMFORD'S NEW EXPERIMENTS 



Time of the ex- 

 periment. . 



Hence light does 

 not give more 

 heat abfolutely 

 by being con- 

 denfed. 



The rays were 

 convergent in 

 the preceding 

 experiments. 



This experiment was begun at 7 minutes 30 feconds after 

 II, and finimed at 22 minutes 40 feconds after 12, the iky 

 being perfeclly clear during the time. 



On comparing all the remits of this experiment, we fee, 

 that the refervoir A, which was placed very near the focus, was 

 more flowly heated than the refervoir B, which was at a consi- 

 derable diftance from it*. The differences of time however 

 taken to heat them an equal number of degrees were very 

 trifling, and I think may be eafily explained, without fuppo- 

 fing the condenfation of light to increafe (qu. diminiih?) its 

 faculiy of exciting heat. 



In both the preceding experiments the folar rays ftriking on 

 the refervoirs of heat were convergent, and they were even 

 equally fo on both fides. To determine whether parallel rays 

 have the fame power of exciting heat as convergent rays, I 

 made the following experiment. 



Experiment III. 

 When one vefTel Having removed the lens from before the refervoir B, Ifuf- 



ScparaHefra^s fered the direa fa >' S of the fu " t0 h]l ° U the b,ackened face of 



of the fun with- the refervoir, through the circular hole three inches and half 

 out interception, ; n diameter in the round brafs plate, which had been conftantly 



placed before that lens in the preceding experiments. 



The refervoir A. was placed behind its lens as in the former 



experiments, and at the place where the folar fpe£irum had fix 



lines diameter. 



* Did not the elevated temperature of the fmaller furface fuftain 

 its power of abforbing heat, conformably to the known laws of heated 

 bodies? — N. 



Having 



