40 Inquiry concerning the Nature of Heat, 



Time employed in cooling through 



the given interval of 10 degrees. 



Instrument Instrument 



No. i, No. 2, 



varnished, naked. 



Experiment No. 4. I coating of varnish, 42 min. 55 min. 



Experiment No. 5. 2 coatings, . . 35^ " 55^ " 



Experiment No. 6. 4 coatings, . . 30^ " 55^ " 



Experiment No. 7 . 8 coatings, . . 34^ " 55 " 



Experiment No. 8. Desirous of finding out what 

 effect colour would produce, I now painted the sides of 

 the instrument No. 2 black, with lamp-black mixed up 

 with size (this paint being laid upon the eighth coating 

 of the varnish), and, repeating the experiment, its re- 

 sults were as follows : 



Time employed in 



cooling through the 



given interval. 



The instrument No. i, naked, . . . . 55i m ' n - 

 The instrument No. 2, covered with 8 coatings of var- 

 nish, and painted black, ..... 34 " 



Experiment No. 9. Finding that the painting of this 

 thick coating of varnish black rendered the covering 

 still colder, or accelerated the cooling of the instrument, 

 I now washed off the black paint with warm water; 

 then washing off all the varnish with hot spirit of wine, 

 I painted the metallic sides of the instrument of a black 

 colour with lamp-black and size ; and when the paint 

 was quite dry, I repeated the experiment so often men- 

 tioned, when the results were as follows : 



Time employed in 



cooling through the 



given interval. 



The instrument No. i, sides naked, . . . 55& m ' n - 

 The instrument No. 2, painted black, . . . 35 " 



Experiment No. 10. In order to find out whether 

 the black colour had any particular efficacy in expediting 

 the cooling of the instrument, or whether another colour- 

 ing substance would not produce the same effect, when 



