A HISTORY OF SCIENCE 



statement and explanation of several of these will form 

 the concluding part of the present essay. 



" i. I observed one morning, in winter, that the in- 

 sides of the panes of glass in the windows of my bed- 

 chamber were all of them moist, but that those which 

 had been covered by an inside shutter during the night 

 were much more so than the others which had been 

 uncovered. Supposing that this diversity of appear- 

 ance depended upon a difference of temperature, I 

 applied the naked bulbs of two delicate thermometers 

 to a covered and uncovered pane; on which I found 

 that the former was three degrees colder than the 

 latter. The air of the chamber, though no fire was 

 kept in it, was at this time eleven and one-half de- 

 grees warmer than that without. Similar experiments 

 were made on many other mornings, the results of 

 which were that the warmth' of the internal air ex- 

 ceeded that of the external from eight to eighteen de- 

 grees, the temperature of the covered panes would be 

 from one to five degrees less than the uncovered ; that 

 the covered were sometimes dewed, while the uncov- 

 ered were dry ; that at other times both were free from 

 moisture ; that the outsides of the covered and uncov- 

 ered panes had similar differences with respect to heat, 

 though not so great as those of the inner surfaces ; and 

 that no variation in the quantity of these differences 

 was occasioned by the weather's being cloudy or fair, 

 provided the heat of the internal air exceeded that of 

 the external equally in both of those states of the 

 atmosphere. 



"The remote reason of these differences did not im- 

 mediately present itself. I soon, however, saw that 



1 88 



